--- gcc/internals-1 2018/04/24 16:37:52 1.1 +++ gcc/internals-1 2018/04/24 16:40:34 1.1.1.4 @@ -1,157 +1,180 @@ -Info file internals, produced by texinfo-format-buffer -*-Text-*- -from file internals.texinfo - +Info file internals, produced by Makeinfo, -*- Text -*- from input +file internals.texinfo. This file documents the internals of the GNU compiler. -Copyright (C) 1987 Richard M. Stallman. +Copyright (C) 1988 Free Software Foundation, Inc. -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled "GNU CC General Public License" is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled "GNU CC General Public License" may be -included in a translation approved by the author instead of in the original +Permission is granted to make and distribute verbatim copies of this +manual provided the copyright notice and this permission notice are +preserved on all copies. + +Permission is granted to copy and distribute modified versions of +this manual under the conditions for verbatim copying, provided also +that the section entitled ``GNU CC General Public License'' is +included exactly as in the original, and provided that the entire +resulting derived work is distributed under the terms of a permission +notice identical to this one. + +Permission is granted to copy and distribute translations of this +manual into another language, under the above conditions for modified +versions, except that the section entitled ``GNU CC General Public +License'' and this permission notice may be included in translations +approved by the Free Software Foundation instead of in the original English. - -  -File: internals Node: Top, Up: (DIR), Next: Switches +File: internals, Node: Top, Next: Copying, Up: (DIR) Introduction ************ -This manual documents how to install and port the GNU C compiler. +This manual documents how to run, install and port the GNU C +compiler, as well as its new features and incompatibilities, and how +to report bugs. * Menu: * Copying:: GNU CC General Public License says how you can copy and share GNU CC. -* Switches:: Command switches supported by `gcc'. +* Contributors:: People who have contributed to GNU CC. +* Options:: Command options supported by `gcc'. * Installation:: How to configure, compile and install GNU CC. +* Trouble:: If you have trouble installing GNU CC. +* Incompatibilities:: Incompatibilities of GNU CC. +* Extensions:: GNU extensions to the C language. +* Bugs:: How to report bugs (if you want to get them fixed). * Portability:: Goals of GNU CC's portability features. +* Interface:: Function-call interface of GNU CC output. * Passes:: Order of passes, what they do, and what each file is for. * RTL:: The intermediate representation that most passes work on. * Machine Desc:: How to write machine description instruction patterns. * Machine Macros:: How to write the machine description C macros. +  -File: internals Node: Copying, Prev: Top, Up: Top, Next: Switches +File: internals, Node: Copying, Next: Contributors, Prev: Top, Up: Top GNU CC GENERAL PUBLIC LICENSE ***************************** + (Clarified 11 Feb 1988) + The license agreements of most software companies keep you at the mercy of those companies. By contrast, our general public license is -intended to give everyone the right to share GNU CC. To make sure that -you get the rights we want you to have, we need to make restrictions -that forbid anyone to deny you these rights or to ask you to surrender -the rights. Hence this license agreement. +intended to give everyone the right to share GNU CC. To make sure +that you get the rights we want you to have, we need to make +restrictions that forbid anyone to deny you these rights or to ask +you to surrender the rights. Hence this license agreement. Specifically, we want to make sure that you have the right to give -away copies of GNU CC, that you receive source code or else can get it -if you want it, that you can change GNU CC or use pieces of it in new -free programs, and that you know you can do these things. +away copies of GNU CC, that you receive source code or else can get +it if you want it, that you can change GNU CC or use pieces of it in +new free programs, and that you know you can do these things. To make sure that everyone has such rights, we have to forbid you to deprive anyone else of these rights. For example, if you distribute -copies of GNU CC, you must give the recipients all the rights that you -have. You must make sure that they, too, receive or can get the +copies of GNU CC, you must give the recipients all the rights that +you have. You must make sure that they, too, receive or can get the source code. And you must tell them their rights. Also, for our own protection, we must make certain that everyone -finds out that there is no warranty for GNU CC. If GNU CC is modified by -someone else and passed on, we want its recipients to know that what -they have is not what we distributed, so that any problems introduced -by others will not reflect on our reputation. +finds out that there is no warranty for GNU CC. If GNU CC is +modified by someone else and passed on, we want its recipients to +know that what they have is not what we distributed, so that any +problems introduced by others will not reflect on our reputation. - Therefore we (Richard Stallman and the Free Software Fundation, + Therefore we (Richard Stallman and the Free Software Foundation, Inc.) make the following terms which say what you must do to be allowed to distribute or change GNU CC. - COPYING POLICIES ================ - 1. You may copy and distribute verbatim copies of GNU CC source code as - you receive it, in any medium, provided that you conspicuously and - appropriately publish on each copy a valid copyright notice - "Copyright (C) 1987 Free Software Foundation, Inc." (or - with the year updated if that is appropriate); keep intact the notices - on all files that refer to this License Agreement and to the absence - of any warranty; and give any other recipients of the GNU CC program a - copy of this License Agreement along with the program. You may charge - a distribution fee for the physical act of transferring a copy. - - 2. You may modify your copy or copies of GNU CC or any portion of it, - and copy and distribute such modifications under the terms of - Paragraph 1 above, provided that you also do the following: - + 1. You may copy and distribute verbatim copies of GNU CC source + code as you receive it, in any medium, provided that you + conspicuously and appropriately publish on each copy a valid + copyright notice ``Copyright (C) 1988 Free Software Foundation, + Inc.'' (or with whatever year is appropriate); keep intact the + notices on all files that refer to this License Agreement and to + the absence of any warranty; and give any other recipients of + the GNU CC program a copy of this License Agreement along with + the program. You may charge a distribution fee for the physical + act of transferring a copy. + + 2. You may modify your copy or copies of GNU CC or any portion of + it, and copy and distribute such modifications under the terms + of Paragraph 1 above, provided that you also do the following: + * cause the modified files to carry prominent notices stating that you changed the files and the date of any change; and - + * cause the whole of any work that you distribute or publish, - that in whole or in part contains or is a derivative of GNU CC or - any part thereof, to be licensed at no charge to all third - parties on terms identical to those contained in this License - Agreement (except that you may choose to grant more extensive - warranty protection to some or all third parties, at your - option). - + that in whole or in part contains or is a derivative of GNU + CC or any part thereof, to be licensed at no charge to all + third parties on terms identical to those contained in this + License Agreement (except that you may choose to grant more + extensive warranty protection to some or all third parties, + at your option). + * You may charge a distribution fee for the physical act of - transferring a copy, and you may at your option offer warranty - protection in exchange for a fee. - - 3. You may copy and distribute GNU CC or any portion of it in - compiled, executable or object code form under the terms of Paragraphs - 1 and 2 above provided that you do the following: - - * cause each such copy to be accompanied by the - corresponding machine-readable source code, which must - be distributed under the terms of Paragraphs 1 and 2 above; or, - - * cause each such copy to be accompanied by a - written offer, with no time limit, to give any third party - free (except for a nominal shipping charge) a machine readable - copy of the corresponding source code, to be distributed + transferring a copy, and you may at your option offer + warranty protection in exchange for a fee. + + Mere aggregation of another unrelated program with this program + (or its derivative) on a volume of a storage or distribution + medium does not bring the other program under the scope of these + terms. + + 3. You may copy and distribute GNU CC (or a portion or derivative + of it, under Paragraph 2) in object code or executable form + under the terms of Paragraphs 1 and 2 above provided that you + also do one of the following: + + * accompany it with the complete corresponding + machine-readable source code, which must be distributed under the terms of Paragraphs 1 and 2 above; or, - - * in the case of a recipient of GNU CC in compiled, executable - or object code form (without the corresponding source code) you - shall cause copies you distribute to be accompanied by a copy - of the written offer of source code which you received along - with the copy you received. - + + * accompany it with a written offer, valid for at least three + years, to give any third party free (except for a nominal + shipping charge) a complete machine-readable copy of the + corresponding source code, to be distributed under the + terms of Paragraphs 1 and 2 above; or, + + * accompany it with the information you received as to where + the corresponding source code may be obtained. (This + alternative is allowed only for noncommercial distribution + and only if you received the program in object code or + executable form alone.) + + For an executable file, complete source code means all the + source code for all modules it contains; but, as a special + exception, it need not include source code for modules which are + standard libraries that accompany the operating system on which + the executable file runs. + 4. You may not copy, sublicense, distribute or transfer GNU CC - except as expressly provided under this License Agreement. Any attempt - otherwise to copy, sublicense, distribute or transfer GNU CC is void and - your rights to use the program under this License agreement shall be - automatically terminated. However, parties who have received computer - software programs from you with this License Agreement will not have - their licenses terminated so long as such parties remain in full compliance. - - 5. If you wish to incorporate parts of GNU CC into other free programs - whose distribution conditions are different, write to the Free Software - Foundation at 1000 Mass Ave, Cambridge, MA 02138. We have not yet worked - out a simple rule that can be stated here, but we will often permit this. - We will be guided by the two goals of preserving the free status of all - derivatives our free software and of promoting the sharing and reuse of - software. + except as expressly provided under this License Agreement. Any + attempt otherwise to copy, sublicense, distribute or transfer + GNU CC is void and your rights to use the program under this + License agreement shall be automatically terminated. However, + parties who have received computer software programs from you + with this License Agreement will not have their licenses + terminated so long as such parties remain in full compliance. + + 5. If you wish to incorporate parts of GNU CC into other free + programs whose distribution conditions are different, write to + the Free Software Foundation at 675 Mass Ave, Cambridge, MA + 02139. We have not yet worked out a simple rule that can be + stated here, but we will often permit this. We will be guided + by the two goals of preserving the free status of all + derivatives of our free software and of promoting the sharing + and reuse of software. Your comments and suggestions about our licensing policies and our -software are welcome! Please contact the Free Software Foundation, Inc., -1000 Mass Ave, Cambridge, MA 02138, or call (617) 876-3296. - +software are welcome! Please contact the Free Software Foundation, +Inc., 675 Mass Ave, Cambridge, MA 02139, or call (617) 876-3296. NO WARRANTY =========== @@ -159,1014 +182,1029 @@ NO WARRANTY BECAUSE GNU CC IS LICENSED FREE OF CHARGE, WE PROVIDE ABSOLUTELY NO WARRANTY, TO THE EXTENT PERMITTED BY APPLICABLE STATE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING, FREE SOFTWARE FOUNDATION, INC, -RICHARD M. STALLMAN AND/OR OTHER PARTIES PROVIDE GNU CC "AS IS" WITHOUT -WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT -LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR -A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND -PERFORMANCE OF GNU CC IS WITH YOU. SHOULD GNU CC PROVE DEFECTIVE, YOU -ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. +RICHARD M. STALLMAN AND/OR OTHER PARTIES PROVIDE GNU CC "AS IS" +WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, +BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND +FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY +AND PERFORMANCE OF GNU CC IS WITH YOU. SHOULD GNU CC PROVE +DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR +CORRECTION. - IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW WILL RICHARD M. + IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW WILL RICHARD M. STALLMAN, THE FREE SOFTWARE FOUNDATION, INC., AND/OR ANY OTHER PARTY -WHO MAY MODIFY AND REDISTRIBUTE GNU CC AS PERMITTED ABOVE, BE LIABLE TO -YOU FOR DAMAGES, INCLUDING ANY LOST PROFITS, LOST MONIES, OR OTHER -SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR -INABILITY TO USE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA -BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY THIRD PARTIES OR A -FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS) GNU CC, EVEN -IF YOU HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, OR FOR -ANY CLAIM BY ANY OTHER PARTY. +WHO MAY MODIFY AND REDISTRIBUTE GNU CC AS PERMITTED ABOVE, BE LIABLE +TO YOU FOR DAMAGES, INCLUDING ANY LOST PROFITS, LOST MONIES, OR OTHER +SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE +OR INABILITY TO USE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR +DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY THIRD PARTIES +OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS) GNU +CC, EVEN IF YOU HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, +OR FOR ANY CLAIM BY ANY OTHER PARTY. + + + +File: internals, Node: Contributors, Next: Options, Prev: Copying, Up: Top + +Contributors to GNU CC +********************** + +In addition to Richard Stallman, several people have written parts of +GNU CC. + + * The idea of using RTL and some of the optimization ideas came + from the U. of Arizona Portable Optimizer, written by Jack + Davidson and Christopher Fraser. See ``Register Allocation and + Exhaustive Peephole Optimization'', Software Practice and + Experience 14 (9), Sept. 1984, 857-866. + + * Paul Rubin wrote most of the preprocessor. + + * Leonard Tower wrote parts of the parser, RTL generator, RTL + definitions, and of the Vax machine description. + + * Ted Lemon wrote parts of the RTL reader and printer. + + * Nobuyuki Hikichi of Software Research Associates, Tokyo, + contributed the support for the SONY NEWS machine. + + * Charles LaBrec contributed the support for the Integrated + Solutions 68020 system. + + * Michael Tiemann of MCC wrote most of the description of the + National Semiconductor 32000 series cpu. He also wrote the code + for inline function integration and for the SPARC cpu and + Motorola 88000 cpu and part of the Sun FPA support. + + * Jan Stein of the Chalmers Computer Society provided support for + Genix, as well as part of the 32000 machine description. + + * Randy Smith finished the Sun FPA support. + + * Robert Brown implemented the support for Encore 32000 systems. + + * David Kashtan of SRI adapted GNU CC to the Vomit-Making System. + + * Alex Crain provided changes for the 3b1. + + * Greg Satz and Chris Hanson assisted in making GNU CC work on + HP-UX for the 9000 series 300. + + * William Schelter did most of the work on the Intel 80386 support. +  -File: internals Node: Switches, Prev: Copying, Up: Top, Next: Installation +File: internals, Node: Options, Next: Installation, Prev: Contributors, Up: Top + +GNU CC Command Options +********************** -GNU CC Switches -*************** +The GNU C compiler uses a command syntax much like the Unix C compiler. +The `gcc' program accepts options and file names as operands. +Multiple single-letter options may *not* be grouped: `-dr' is very +different from `-d -r'. + +When you invoke GNU CC, it normally does preprocessing, compilation, +assembly and linking. File names which end in `.c' are taken as C +source to be preprocessed and compiled; compiler output files plus +any input files with names ending in `.s' are assembled; then the +resulting object files, plus any other input files, are linked +together to produce an executable. + +Command options allow you to stop this process at an intermediate +stage. For example, the `-c' option says not to run the linker. +Then the output consists of object files output by the assembler. + +Other command options are passed on to one stage. Some options +control the preprocessor and others the compiler itself. Yet other +options control the assembler and linker; these are not documented +here because the GNU assembler and linker are not yet released. + +Here are the options to control the overall compilation process, +including those that say whether to link, whether to assemble, and so +on. + +`-o FILE' + Place output in file FILE. This applies regardless to whatever + sort of output is being produced, whether it be an executable + file, an object file, an assembler file or preprocessed C code. + + If `-o' is not specified, the default is to put an executable + file in `a.out', the object file `SOURCE.c' in `SOURCE.o', an + assembler file in `SOURCE.s', and preprocessed C on standard + output. + +`-c' + Compile or assemble the source files, but do not link. Produce + object files with names made by replacing `.c' or `.s' with `.o' + at the end of the input file names. Do nothing at all for + object files specified as input. + +`-S' + Compile into assembler code but do not assemble. The assembler + output file name is made by replacing `.c' with `.s' at the end + of the input file name. Do nothing at all for assembler source + files or object files specified as input. + +`-E' + Run only the C preprocessor. Preprocess all the C source files + specified and output the results to standard output. + +`-v' + Compiler driver program prints the commands it executes as it + runs the preprocessor, compiler proper, assembler and linker. + Some of these are directed to print their own version numbers. + +`-BPREFIX' + Compiler driver program tries PREFIX as a prefix for each + program it tries to run. These programs are `cpp', `cc1', `as' + and `ld'. + + For each subprogram to be run, the compiler driver first tries + the `-B' prefix, if any. If that name is not found, or if `-B' + was not specified, the driver tries two standard prefixes, which + are `/usr/lib/gcc-' and `/usr/local/lib/gcc-'. If neither of + those results in a file name that is found, the unmodified + program name is searched for using the directories specified in + your `PATH' environment variable. + + The run-time support file `gnulib' is also searched for using + the `-B' prefix, if needed. If it is not found there, the two + standard prefixes above are tried, and that is all. The file is + left out of the link if it is not found by those means. Most of + the time, on most machines, you can do without it. + +These options control the details of C compilation itself. + +`-ansi' + Support all ANSI standard C programs. + + This turns off certain features of GNU C that are incompatible + with ANSI C, such as the `asm', `inline' and `typeof' keywords, + and predefined macros such as `unix' and `vax' that identify the + type of system you are using. It also enables the undesirable + and rarely used ANSI trigraph feature. + + The `-ansi' option does not cause non-ANSI programs to be + rejected gratuitously. For that, `-pedantic' is required in + addition to `-ansi'. + + The macro `__STRICT_ANSI__' is predefined when the `-ansi' + option is used. Some header files may notice this macro and + refrain from declaring certain functions or defining certain + macros that the ANSI standard doesn't call for; this is to avoid + interfering with any programs that might use these names for + other things. + +`-traditional' + Attempt to support some aspects of traditional C compilers. + Specifically: + + * All `extern' declarations take effect globally even if they + are written inside of a function definition. This includes + implicit declarations of functions. + + * The keywords `typeof', `inline', `signed', `const' and + `volatile' are not recognized. + + * Comparisons between pointers and integers are always allowed. + + * Integer types `unsigned short' and `unsigned char' promote + to `unsigned int'. + + * Out-of-range floating point literals are not an error. + + * In the preprocessor, comments convert to nothing at all, + rather than to a space. This allows traditional token + concatenation. + + * In the preprocessor, macro arguments are recognized within + string constants in a macro definition (and their values + are stringified, though without additional quote marks, + when they appear in such a context). The preprocessor + always considers a string constant to end at a newline. + +`-O' + Optimize. Optimizing compilation takes somewhat more time, and + a lot more memory for a large function. + + Without `-O', the compiler's goal is to reduce the cost of + compilation and to make debugging produce the expected results. + Statements are independent: if you stop the program with a + breakpoint between statements, you can then assign a new value + to any variable or change the program counter to any other + statement in the function and get exactly the results you would + expect from the source code. + + Without `-O', only variables declared `register' are allocated + in registers. The resulting compiled code is a little worse + than produced by PCC without `-O'. + + With `-O', the compiler tries to reduce code size and execution + time. + + Some of the `-f' options described below turn specific kinds of + optimization on or off. + +`-g' + Produce debugging information in the operating system's native + format (for DBX or SDB). + + Unlike most other C compilers, GNU CC allows you to use `-g' + with `-O'. The shortcuts taken by optimized code may + occasionally produce surprising results: some variables you + declared may not exist at all; flow of control may briefly move + where you did not expect it; some statements may not be executed + because they compute constant results or their values were + already at hand; some statements may execute in different places + because they were moved out of loops. Nevertheless it proves + possible to debug optimized output. This makes it reasonable to + use the optimizer for programs that might have bugs. + +`-gg' + Produce debugging information in GDB's own format. This + requires the GNU assembler and linker in order to work. + +`-w' + Inhibit all warning messages. + +`-W' + Print extra warning messages for these events: + + * An automatic variable is used without first being + initialized. + + These warnings are possible only in optimizing compilation, + because they require data flow information that is computed + only when optimizing. They occur only for variables that + are candidates for register allocation. Therefore, they do + not occur for a variable that is declared `volatile', or + whose address is taken, or whose size is other than 1, 2, 4 + or 8 bytes. Also, they do not occur for structures, unions + or arrays, even when they are in registers. + + Note that there may be no warning about a variable that is + used only to compute a value that itself is never used, + because such computations may be deleted by the flow + analysis pass before the warnings are printed. + + These warnings are made optional because GNU CC is not + smart enough to see all the reasons why the code might be + correct despite appearing to have an error. Here is one + example of how this can happen: + + { + int x; + switch (y) + { + case 1: x = 1; + break; + case 2: x = 4; + break; + case 3: x = 5; + } + foo (x); + } + + If the value of `y' is always 1, 2 or 3, then `x' is always + initialized, but GNU CC doesn't know this. Here is another + common case: + + { + int save_y; + if (change_y) save_y = y, y = new_y; + ... + if (change_y) y = save_y; + } + + This has no bug because `save_y' is used only if it is set. + + * A nonvolatile automatic variable might be changed by a call + to `longjmp'. These warnings as well are possible only in + optimizing compilation. + + The compiler sees only the calls to `setjmp'. It cannot + know where `longjmp' will be called; in fact, a signal + handler could call it at any point in the code. As a + result, you may get a warning even when there is in fact no + problem because `longjmp' cannot in fact be called at the + place which would cause a problem. + + * A function can return either with or without a value. + (Falling off the end of the function body is considered + returning without a value.) For example, this function + would inspire such a warning: + + foo (a) + { + if (a > 0) + return a; + } + + Spurious warnings can occur because GNU CC does not realize + that certain functions (including `abort' and `longjmp') + will never return. + + In the future, other useful warnings may also be enabled by this + option. + +`-Wimplicit' + Warn whenever a function is implicitly declared. + +`-Wreturn-type' + Warn whenever a function is defined with a return-type that + defaults to `int'. Also warn about any `return' statement with + no return-value in a function whose return-type is not `void'. + +`-Wcomment' + Warn whenever a comment-start sequence `/*' appears in a comment. + +`-Wall' + All of the above `-W' options combined. + +`-Wwrite-strings' + Give string constants the type `const char[LENGTH]' so that + copying the address of one into a non-`const' `char *' pointer + will get a warning. These warnings will help you find at + compile time code that can try to write into a string constant, + but only if you have been very careful about using `const' in + declarations and prototypes. Otherwise, it will just be a + nuisance; this is why we did not make `-Wall' request these + warnings. + +`-p' + Generate extra code to write profile information suitable for + the analysis program `prof'. + +`-pg' + Generate extra code to write profile information suitable for + the analysis program `gprof'. + +`-lLIBRARY' + Search a standard list of directories for a library named + LIBRARY, which is actually a file named `libLIBRARY.a'. The + linker uses this file as if it had been specified precisely by + name. + + The directories searched include several standard system + directories plus any that you specify with `-L'. + + Normally the files found this way are library files--archive + files whose members are object files. The linker handles an + archive file by scanning through it for members which define + symbols that have so far been referenced but not defined. But + if the file that is found is an ordinary object file, it is + linked in the usual fashion. The only difference between using + an `-l' option and specifying a file name is that `-l' searches + several directories. + +`-LDIR' + Add directory DIR to the list of directories to be searched for + `-l'. + +`-nostdlib' + Don't use the standard system libraries and startup files when + linking. Only the files you specify (plus `gnulib') will be + passed to the linker. + +`-mMACHINESPEC' + Machine-dependent option specifying something about the type of + target machine. These options are defined by the macro + `TARGET_SWITCHES' in the machine description. The default for + the options is also defined by that macro, which enables you to + change the defaults. + + These are the `-m' options defined in the 68000 machine + description: + + `-m68020' + `-mc68020' + Generate output for a 68020 (rather than a 68000). This is + the default if you use the unmodified sources. + + `-m68000' + `-mc68000' + Generate output for a 68000 (rather than a 68020). + + `-m68881' + Generate output containing 68881 instructions for floating + point. This is the default if you use the unmodified + sources. + + `-mfpa' + Generate output containing Sun FPA instructions for + floating point. + + `-msoft-float' + Generate output containing library calls for floating point. + + `-mshort' + Consider type `int' to be 16 bits wide, like `short int'. + + `-mnobitfield' + Do not use the bit-field instructions. `-m68000' implies + `-mnobitfield'. + + `-mbitfield' + Do use the bit-field instructions. `-m68020' implies + `-mbitfield'. This is the default if you use the + unmodified sources. + + `-mrtd' + Use a different function-calling convention, in which + functions that take a fixed number of arguments return with + the `rtd' instruction, which pops their arguments while + returning. This saves one instruction in the caller since + there is no need to pop the arguments there. + + This calling convention is incompatible with the one + normally used on Unix, so you cannot use it if you need to + call libraries compiled with the Unix compiler. + + Also, you must provide function prototypes for all + functions that take variable numbers of arguments + (including `printf'); otherwise incorrect code will be + generated for calls to those functions. + + In addition, seriously incorrect code will result if you + call a function with too many arguments. (Normally, extra + arguments are harmlessly ignored.) + + The `rtd' instruction is supported by the 68010 and 68020 + processors, but not by the 68000. + + These `-m' options are defined in the Vax machine description: + + `-munix' + Do not output certain jump instructions (`aobleq' and so + on) that the Unix assembler for the Vax cannot handle + across long ranges. + + `-mgnu' + Do output those jump instructions, on the assumption that + you will assemble with the GNU assembler. + + `-mg' + Output code for g-format floating point numbers instead of + d-format. + +`-fFLAG' + Specify machine-independent flags. These are the flags: + + `-ffloat-store' + Do not store floating-point variables in registers. This + prevents undesirable excess precision on machines such as + the 68000 where the floating registers (of the 68881) keep + more precision than a `double' is supposed to have. + + For most programs, the excess precision does only good, but + a few programs rely on the precise definition of IEEE + floating point. Use `-ffloat-store' for such programs. + + `-fno-asm' + Do not recognize `asm', `inline' or `typeof' as a keyword. + These words may then be used as identifiers. + + `-fno-defer-pop' + Always pop the arguments to each function call as soon as + that function returns. Normally the compiler (when + optimizing) lets arguments accumulate on the stack for + several function calls and pops them all at once. + + `-fcombine-regs' + Allow the combine pass to combine an instruction that + copies one register into another. This might or might not + produce better code when used in addition to `-O'. I am + interested in hearing about the difference this makes. + + `-fforce-mem' + Force memory operands to be copied into registers before + doing arithmetic on them. This may produce better code by + making all memory references potential common + subexpressions. When they are not common subexpressions, + instruction combination should eliminate the separate + register-load. I am interested in hearing about the + difference this makes. + + `-fforce-addr' + Force memory address constants to be copied into registers + before doing arithmetic on them. This may produce better + code just as `-fforce-mem' may. I am interested in hearing + about the difference this makes. + + `-fomit-frame-pointer' + Don't keep the frame pointer in a register for functions + that don't need one. This avoids the instructions to save, + set up and restore frame pointers; it also makes an extra + register available in many functions. *It also makes + debugging impossible.* + + On some machines, such as the Vax, this flag has no effect, + because the standard calling sequence automatically handles + the frame pointer and nothing is saved by pretending it + doesn't exist. The machine-description macro + `FRAME_POINTER_REQUIRED' controls whether a target machine + supports this flag. *Note Registers::. + + `-finline-functions' + Integrate all simple functions into their callers. The + compiler heuristically decides which functions are simple + enough to be worth integrating in this way. + + If all calls to a given function are integrated, and the + function is declared `static', then the function is + normally not output as assembler code in its own right. + + `-fkeep-inline-functions' + Even if all calls to a given function are integrated, and + the function is declared `static', nevertheless output a + separate run-time callable version of the function. + + `-fwritable-strings' + Store string constants in the writable data segment and + don't uniquize them. This is for compatibility with old + programs which assume they can write into string constants. + Writing into string constants is a very bad idea; + ``constants'' should be constant. + + `-fno-function-cse' + Do not put function addresses in registers; make each + instruction that calls a constant function contain the + function's address explicitly. + + This option results in less efficient code, but some + strange hacks that alter the assembler output may be + confused by the optimizations performed when this option is + not used. + + `-fvolatile' + Consider all memory references through pointers to be + volatile. + + `-funsigned-char' + Let the type `char' be the unsigned, like `unsigned char'. + + Each kind of machine has a default for what `char' should + be. It is either like `unsigned char' by default or like + `signed char' by default. (Actually, at present, the + default is always signed.) + + The type `char' is always a distinct type from either + `signed char' or `unsigned char', even though its behavior + is always just like one of those two. + + `-fsigned-char' + Let the type `char' be signed, like `signed char'. + + `-ffixed-REG' + Treat the register named REG as a fixed register; generated + code should never refer to it (except perhaps as a stack + pointer, frame pointer or in some other fixed role). + + REG must be the name of a register. The register names + accepted are machine-specific and are defined in the + `REGISTER_NAMES' macro in the machine description macro file. + + `-fcall-used-REG' + Treat the register named REG as an allocatable register + that is clobbered by function calls. It may be allocated + for temporaries or variables that do not live across a call. + Functions compiled this way will not save and restore the + register REG. + + Use of this flag for a register that has a fixed pervasive + role in the machine's execution model, such as the stack + pointer or frame pointer, will produce disastrous results. + + `-fcall-saved-REG' + Treat the register named REG as an allocatable register + saved by functions. It may be allocated even for + temporaries or variables that live across a call. + Functions compiled this way will save and restore the + register REG if they use it. + + Use of this flag for a register that has a fixed pervasive + role in the machine's execution model, such as the stack + pointer or frame pointer, will produce disastrous results. + + A different sort of disaster will result from the use of + this flag for a register in which function values are may + be returned. -`-O' - Do optimize. - -`-g' - Produce debugging information in DBX format. - -`-c' - Compile but do not link the object files. - -`-o FILE' - Place linker output in file FILE. - -`-S' - Compile into assembler code but do not assemble. - -`-mMACHINESPEC' - Machine-dependent switch specifying something about the type - of target machine. For example, using the 68000 machine description, - `-m68000' specifies do not use the 68020 instructions, - and `-msoft-float' specifies do not use the 68881 floating point - instructions. - -`-dLETTERS' - Says to make debugging dumps at times specified by LETTERS. +`-dLETTERS' + Says to make debugging dumps at times specified by LETTERS. Here are the possible letters: - - `t' - Dump syntax-tree. - `r' + + `r' Dump after RTL generation. - `j' + + `j' Dump after first jump optimization. - `s' - Dump after CSE. - `L' + + `J' + Dump after last jump optimization. + + `s' + Dump after CSE (including the jump optimization that + sometimes follows CSE). + + `L' Dump after loop optimization. - `f' + + `f' Dump after flow analysis. - `c' + + `c' Dump after instruction combination. - `l' + + `l' Dump after local register allocation. - `g' + + `g' Dump after global register allocation. - -`-pedantic' - Attempt to support strict ANSI standard C. Valid ANSI standard C - programs should compile properly with or without this switch. - However, without this switch, certain useful or traditional constructs - banned by the standard are supported. With this switch, they are - rejected. There is no reason to use this switch; it exists only - to satisfy pedants. - -`E' - Preprocess the input files and output the results to standard output. - -`C' - Tell the preprocessor not to discard comments. Used with the `-E' - switch. - -`IDIR' + + `m' + Print statistics on memory usage, at the end of the run. + +`-pedantic' + Issue all the warnings demanded by strict ANSI standard C; + reject all programs that use forbidden extensions. + + Valid ANSI standard C programs should compile properly with or + without this option (though a rare few will require `-ansi'). + However, without this option, certain GNU extensions and + traditional C features are supported as well. With this option, + they are rejected. There is no reason to use this option; it + exists only to satisfy pedants. + +These options control the C preprocessor, which is run on each C +source file before actual compilation. If you use the `-E' option, +nothing is done except C preprocessing. Some of these options make +sense only together with `-E' because they request preprocessor +output that is not suitable for actual compilation. + +`-C' + Tell the preprocessor not to discard comments. Used with the + `-E' option. + +`-IDIR' Search directory DIR for include files. - -`DMACRO' + +`-I-' + Any directories specified with `-I' options before the `-I-' + option are searched only for the case of `#include "FILE"'; they + are not searched for `#include '. + + If additional directories are specified with `-I' options after + the `-I-', these directories are searched for all `#include' + directives. (Ordinarily *all* `-I' directories are used this + way.) + + In addition, the `-I-' option inhibits the use of the current + directory as the first search directory for `#include "FILE"'. + Therefore, the current directory is searched only if it is + requested explicitly with `-I.'. Specifying both `-I-' and + `-I.' allows you to control precisely which directories are + searched before the current one and which are searched after. + +`-nostdinc' + Do not search the standard system directories for header files. + Only the directories you have specified with `-I' options (and + the current directory, if appropriate) are searched. + + Between `-nostdinc' and `-I-', you can eliminate all directories + from the search path except those you specify. + +`-M' + Tell the preprocessor to output a rule suitable for `make' + describing the dependencies of each source file. For each + source file, the preprocessor outputs one `make'-rule whose + target is the object file name for that source file and whose + dependencies are all the files `#include'd in it. This rule may + be a single line or may be continued with `\'-newline if it is + long. + + `-M' implies `-E'. + +`-MM' + Like `-M' but the output mentions only the user-header files + included with `#include "FILE"'. System header files included + with `#include ' are omitted. + + `-MM' implies `-E'. + +`-DMACRO' Define macro MACRO with the empty string as its definition. - -`DMACRO=DEFN' + +`-DMACRO=DEFN' Define macro MACRO as DEFN. - -`UMACRO' + +`-UMACRO' Undefine macro MACRO. - -`w' - Inhibit warning messages. - -`v' - Compiler driver program prints the commands it executes as it runs - the preprocessor, compiler proper, assembler and linker. - -`BPREFIX' - Compiler driver program tries PREFIX as a prefix for each program - it tries to run. These programs are `cpp', `cc1', - `as' and `ld'. - - For each subprogram to be run, the compiler driver first tries the - `-B' prefix, if any. If that name is not found, or if `-B' - was not specified, the driver tries two standard prefixes, which are - `/usr/lib/gcc-' and `/usr/local/lib/gcc-'. If neither of - those results in a file name that is found, the unmodified program - name is searched for using the `PATH' environment variable. + +`-T' + Support ANSI C trigraphs. You don't want to know about this + brain-damage. The `-ansi' option also has this effect. +  -File: internals Node: Installation, Prev: Switches, Up: Top, Next: Portability +File: internals, Node: Installation, Next: Trouble, Prev: Options, Up: Top Installing GNU CC ***************** - 1. Choose configuration files. - - * Make a symbolic link from file `config.h' to the top-level - config file for the machine you are using. Its name should be - `config-MACHINE.h'. This file is responsible for - defining information about the host machine. It includes - `tm.h'. - - * Make a symbolic link from `tm.h' to the machine-description - macro file for your machine (its name should be - `tm-MACHINE.h'). - - * Make a symbolic link from `md' to the - machine description pattern file (its name should be - `MACHINE.md'). - - * Make a symbolic link from - `aux-output.c' to the output-subroutine file for your machine - (its name should be `MACHINE-output.c'). - - 2. Make sure the Bison parser generator is installed. - - 3. Build the compiler. Just type `make' in the compiler directory. - - 4. Delete `*.o' in the compiler directory. The executables from - the previous step remain for the next step. - - 5. Remake the compiler with - - make CC=./gcc CFLAGS="-g -O -I." - - 6. Install the compiler's passes. Copy the file `cc1' just made - to `/usr/local/lib/gcc-cc1'. - - Make the file `/usr/local/lib/gcc-cpp' either a link to `/lib/cpp' - or a copy of the file `cpp' generated by `make'. - - *Warning: the GNU CPP may not work for @file{ioctl.h}.* This - cannot be fixed in the GNU CPP because the bug is in `ioctl.h': - at least on some machines, it relies on behavior that is incompatible - with ANSI C. This behavior consists of substituting for macro - argument names when they appear inside of character constants. - - 7. Install the compiler driver. This is the file `gcc' generated - by `make'. +Here is the procedure for installing GNU CC on a Unix system. - -File: internals Node: Portability, Prev: Installation, Up: Top, Next: Passes +* Menu: -GNU CC and Portability -********************** +* VMS Install:: See below for installation on VMS. -The main goal of GNU CC was to make a good, fast compiler for machines in -the class that the GNU system aims to run on: 32-bit machines that address -8-bit bytes and have several general registers. Elegance, theoretical -power and simplicity are only secondary. - -GNU CC gets most of the information about the target machine from a machine -description which gives an algebraic formula for each of the machine's -instructions. This is a very clean way to describe the target. But when -the compiler needs information that is difficult to express in this -fashion, I have not hesitated to define an ad-hoc parameter to the machine -description. The purpose of portability is to reduce the total work needed -on the compiler; it was not of interest for its own sake. - -GNU CC does not contain machine dependent code, but it does contain code -that depends on machine parameters such as endianness (whether the most -significant byte has the highest or lowest address of the bytes in a word) -and the availability of autoincrement addressing. In the RTL-generation -pass, it is often necessary to have multiple strategies for generating code -for a particular kind of syntax tree, strategies that are usable for different -combinations of parameters. Often I have not tried to address all possible -cases, but only the common ones or only the ones that I have encountered. -As a result, a new target may require additional strategies. You will know -if this happens because the compiler will call `abort'. Fortunately, -the new strategies can be added to all versions of the compiler, and will -be relevant only for target machines that need them. + 1. Edit `Makefile'. If you are using HPUX, or any form of system + V, you must make a few changes described in comments at the + beginning of the file. - -File: internals Node: Passes, Prev: Portability, Up: Top, Next: RTL + 2. On a Sequent system, go to the Berkeley universe. -Passes and Files of the Compiler -******************************** + 3. Choose configuration files. -The overall control structure of the compiler is in `toplev.c'. This -file is responsible for initialization, decoding arguments, opening and -closing files, and sequencing the passes. - -The parsing pass is invoked only once, to parse the entire input. Each -time a complete function definition or top-level data definition is read, -the parsing pass calls the function `rest_of_compilation' in -`toplev.c', which is responsible for all further processing necessary, -ending with output of the assembler language. All other compiler passes -run, in sequence, within `rest_of_compilation'. After -`rest_of_compilation' returns from compiling a function definition, -the storage used for its compilation is entirely freed. - -Here is a list of all the passes of the compiler and their source files. -Also included is a description of where debugging dumps can be requested -with `-d' switches. - - * Parsing. This pass reads the entire text of a function definition, - constructing a syntax tree. The tree representation does not entirely - follow C syntax, because it is intended to support other languages as well. - - C data type analysis is also done in this pass, and every tree node that - represents an expression has a data type attached. Variables are represented - as declaration nodes. - - Constant folding and associative-law simplifications are also done during - this pass. - - The source files of the parsing pass are `parse.y', `decl.c', - `typecheck.c', `stor-layout.c', `fold-const.c', and - `tree.c'. The last three are intended to be language-independent. - There are also header files `parse.h', `c-tree.h', - `tree.h' and `tree.def'. The last two define the format of - the tree representation. - - * RTL generation. This pass converts the tree structure for one - function into RTL code. - - This is where the bulk of target-parameter-dependent code is found, - since often it is necessary for strategies to apply only when certain - standard kinds of instructions are available. The purpose of named - instruction patterns is to provide this information to the RTL - generation pass. - - Optimization is done in this pass for `if'-conditions that are - comparisons, boolean operations or conditional expressions. Tail - recursion is detected at this time also. Decisions are made about how - best to arrange loops and how to output `switch' statements. - - The files of the RTL generation pass are `stmt.c', `expr.c', - `explow.c', `expmed.c', `optabs.c' and `emit-rtl.c'. - Also, the file `insn-emit.c', generated from the machine description - by the program `genemit', is used in this pass. The header files - `expr.h' is used for communication within this pass. - - The header files `insn-flags.h' and `insn-codes.h', generated from - the machine description by the programs `genflags' and `gencodes', - tell this pass which standard names are available for use and which patterns - correspond to them. - - Aside from debugging information output, none of the following passes - refers to the tree structure representation of the function. - - The switch `-dr' causes a debugging dump of the RTL code after this - pass. This dump file's name is made by appending `.rtl' to the - input file name. - - * Jump optimization. This pass simplifies jumps to the following instruction, - jumps across jumps, and jumps to jumps. It deletes unreferenced labels - and unreachable code, except that unreachable code that contains a loop - is not recognized as unreachable in this pass. (Such loops are deleted - later in the basic block analysis.) - - Jump optimization is performed two or three times. The first time is - immediately following RTL generation. - - The source file of this pass is `jump.c'. - - The switch `-dj' causes a debugging dump of the RTL code after this - pass is run for the first time. This dump file's name is made by appending - `.jump' to the input file name. - - * Register scan. This pass finds the first and last use of each - register, as a guide for common subexpression elimination. Its source - is in `regclass.c'. - - * Common subexpression elimination. This pass also does constant - propagation. Its source file is `cse.c'. If constant - propagation causes conditional jumps to become unconditional or to - become no-ops, jump optimization is run again when cse is finished. - - The switch `-ds' causes a debugging dump of the RTL code after - this pass. This dump file's name is made by appending `.cse' to - the input file name. - - * Loop optimization. This pass moves constant expressions out of loops. - Its source file is `loop.c'. - - The switch `-dL' causes a debugging dump of the RTL code after - this pass. This dump file's name is made by appending `.loop' to - the input file name. - - * Stupid register allocation is performed at this point in a - nonoptimizing compilation. It does a little data flow analysis as - well. When stupid register allocation is in use, the next pass - executed is the reloading pass; the others in between are skipped. - The source file is `stupid.c', with header file `stupid.h' - used for communication with the RTL generation pass. - - * Data flow analysis (`flow.c'). This pass divides the program - into basic blocks (and in the process deletes unreachable loops); then - it computes which pseudo-registers are live at each point in the - program, and makes the first instruction that uses a value point at - the instruction that computed the value. - - This pass also deletes computations whose results are never used, and - combines memory references with add or subtract instructions to make - autoincrement or autodecrement addressing. - - The switch `-df' causes a debugging dump of the RTL code after - this pass. This dump file's name is made by appending `.flow' to - the input file name. If stupid register allocation is in use, this - dump file reflects the full results of such allocation. - - * Instruction combination (`combine.c'). This pass attempts to - combine groups of two or three instructions that are related by data - flow into single instructions. It combines the RTL expressions for - the instructions by substitution, simplifies the result using algebra, - and then attempts to match the result against the machine description. - - The switch `-dc' causes a debugging dump of the RTL code after - this pass. This dump file's name is made by appending `.combine' - to the input file name. - - * Register class preferencing. The RTL code is scanned to find out - which register class is best for each pseudo register. The source file - is `regclass.c'. - - * Local register allocation (`local-alloc.c'). This pass allocates - hard registers to pseudo registers that are used only within one basic - block. Because the basic block is linear, it can use fast and powerful - techniques to do a very good job. - - The switch `-dl' causes a debugging dump of the RTL code after - this pass. This dump file's name is made by appending `.lreg' to - the input file name. - - * Global register allocation (`global-alloc.c'). This pass - allocates hard registers for the remaining pseudo registers (those - whose life spans are not contained in one basic block). - - * Reloading. This pass finds instructions that are invalid because a - value has failed to end up in a register, or has ended up in a - register of the wrong kind. It fixes up these instructions by - reloading the problematical values into registers temporarily. - Additional instructions are generated to do the copying. - - Source files are `reload.c' and `reload1.c', plus the header - `reload.h' used for communication between them. - - The switch `-dg' causes a debugging dump of the RTL code after - this pass. This dump file's name is made by appending `.greg' to - the input file name. - - * Jump optimization is repeated, this time including cross-jumping. - - * Final. This pass outputs the assembler code for the function. It is - also responsible for identifying no-op move instructions and spurious - test and compare instructions. The function entry and exit sequences - are generated directly as assembler code in this pass; they never - exist as RTL. Pseudo registers that did not get hard registers are - given stack slots in this pass. - - The source files are `final.c' plus `insn-output.c'; the - latter is generated automatically from the machine description by the - tool `genoutput'. The header file `conditions.h' is used - for communication between these files. - - * Debugging information output. This is run after final because it must - output the stack slot offsets for pseudo registers that did not get - hard registers. Source files are `dbxout.c' for DBX symbol table - format and `symout.c' for GDB's own symbol table format. - -Some additional files are used by all or many passes: - - * Every pass uses `machmode.def', which defines the machine modes. - - * All the passes that work with RTL use the header files `rtl.h' - and `rtl.def', and subroutines in file `rtl.c'. The - tools `gen*' also use these files to read and work with the - machine description RTL. - - * Several passes refer to the header file `insn-config.h' which - contains a few parameters (C macro definitions) generated - automatically from the machine description RTL by the tool - `genconfig'. - - * Several passes use the instruction recognizer, which consists of - `recog.c' and `recog.h', plus the files `insn-recog.c' - and `insn-extract.c' that are generated automatically from the - machine description by the tools `genrecog' and `genextract'. - - * Several passes use the header file `regs.h' which defines the - information recorded about pseudo register usage, `basic-block.h' - which defines the information recorded about basic blocks. - - * `hard-reg-set.h' defines the type `HARD_REG_SET', a bit-vector - with a bit for each hard register, and some macros to manipulate it. - This type is just `int' if the machine has few enough hard registers; - otherwise it is an array of `int' and some of the macros expand - into loops. + * Make a symbolic link named `config.h' to the top-level + config file for the machine you are using (*note + Config::.). This file is responsible for defining + information about the host machine. It includes `tm.h'. - -File: internals Node: RTL, Prev: Passes, Up: Top, Next: Machine Desc + The file's name should be `config-MACHINE.h', with these + exceptions: -RTL Representation -****************** + `config-vms.h' + for vaxen running VMS. -Most of the work of the compiler is done on an intermediate representation -called register tranfer language. In this language, the instructions to be -output are described, pretty much one by one, in an algebraic form that -describes what the instruction does. - -RTL is inspired by Lisp lists. It has both an internal form, made up of -structures that point at other structures, and a textual form that is used -in the machine description and in printed debugging dumps. The textual -form uses nested parentheses to indicate the pointers in the internal form. + `config-vaxv.h' + for vaxen running system V. -* Menu: + `config-i386v.h' + for Intel 80386's running system V. -* RTL Objects:: Expressions vs vectors vs strings vs integers. -* Accessors:: Macros to access expression operands or vector elts. -* Machine Modes:: Describing the size and format of a datum. -* Constants:: Expressions with constant values. -* Regs and Memory:: Expressions representing register contents or memory. -* Arithmetic:: Expressions representing arithmetic on other expressions. -* Comparisons:: Expressions representing comparison of expressions. -* Bit Fields:: Expressions representing bit-fields in memory or reg. -* Conversions:: Extending, truncating, floating or fixing. -* RTL Declarations:: Declaring volatility, constancy, etc. -* Side Effects:: Expressions for storing in registers, etc. -* Incdec:: Embedded side-effects for autoincrement addressing. -* Insns:: Expression types for entire insns. -* Sharing:: Some expressions are unique; others *must* be copied. + `config-sun4.h' + for Suns (model 3 or 4) running *operating system* + version 4. - -File: internals Node: RTL Objects, Prev: RTL, Up: RTL, Next: Accessors + `config-hp9k3.h' + for the HP 9000 series 300. -RTL Object Types -================ + `config-gnx.h' + for the ns32000 running Genix -RTL uses four kinds of objects: expressions, integers, strings and vectors. -Expressions are the most important ones. An RTL expression is a C -structure, but it is usually referred to with a pointer; a type that is -given the typedef name `rtx'. - -An integer is simply an `int', and a string is a `char *'. -Within rtl code, strings appear only inside `symbol_ref' expressions, -but they appear in other contexts in the rtl expressions that make up -machine descriptions. Their written form uses decimal digits. - -A string is a sequence of characters. In core it is represented as a -`char *' in usual C fashion, and they are written in C syntax as well. -However, strings in RTL may never be null. If you write an empty string in -a machine description, it is represented in core as a null pointer rather -than as a pointer to a null character. In certain contexts, these null -pointers instead of strings are valid. - -A vector contains an arbitrary, specified number of pointers to -expressions. The number of elements in the vector is explicitly present in -the vector. The written form of a vector consists of square brackets -(`[...]') surrounding the elements, in sequence and with -whitespace separating them. Vectors of length zero are not created; null -pointers are used instead. - -Expressions are classified by "expression code". The expression code -is a name defined in `rtl.def', which is also (in upper case) a C -enumeration constant. The possible expression codes and their meanings are -machine-independent. The code of an rtx can be extracted with the macro -`GET_CODE (X)' and altered with `PUT_CODE (X, -NEWCODE)'. - -The expression code determines how many operands the expression contains, -and what kinds of objects they are. In RTL, unlike Lisp, you cannot tell -by looking at an operand what kind of object it is. Instead, you must know -from its context---from the expression code of the containing expression. -For example, in an expression of code `subreg', the first operand is -to be regarded as an expression and the second operand as an integer. In -an expression of code `plus', there are two operands, both of which -are to be regarded as expressions. In a `symbol_ref' expression, -there is one operand, which is to be regarded as a string. - -Expressions are written as parentheses containing the name of the -expression type, its flags and machine mode if any, and then the operands -of the expression (separated by spaces). + If your system does not support symbolic links, you might + want to set up `config.h' to contain a `#include' command + which refers to the appropriate file. -In a few contexts a null pointer is valid where an expression is normally -wanted. The written form of this is `(nil)'. + * Make a symbolic link named `tm.h' to the + machine-description macro file for your machine (its name + should be `tm-MACHINE.h'). - -File: internals Node: Accessors, Prev: RTL Objects, Up: RTL, Next: Machine Modes + If your system is a 68000, don't use the file `tm-m68k.h' + directly. Instead, use one of these files: -Access to Operands -================== + `tm-sun3.h' + for Sun 3 machines. -For each expression type `rtl.def' specifies the number of contained -objects and their kinds, with four possibilities: `e' for expression -(actually a pointer to an expression), `i' for integer, `s' for -string, and `E' for vector of expressions. The sequence of letters -for an expression code is called its "format". Thus, the format of -`subreg' is `ei'. - -Two other format characters are used occasionally: `u' and `0'. -`u' is equivalent to `e' except that it is printed differently in -debugging dumps, and `0' means a slot whose contents do not fit any -normal category. `0' slots are not printed at all in dumps, and are -often used in special ways by small parts of the compiler. - -There are macros to get the number of operands and the format of an -expression code: - -`GET_RTX_LENGTH (CODE)' - Number of operands of an rtx of code CODE. - -`GET_RTX_FORMAT (CODE)' - The format of an rtx of code CODE, as a C string. - -Operands of expressions are accessed using the macros `XEXP', -`XINT' and `XSTR'. Each of these macros takes two arguments: an -expression-pointer (rtx) and an operand number (counting from zero). Thus, - - XEXP (x, 2) - -accesses operand 2 of expression X, as an expression. - - XINT (x, 2) - -accesses the same operand as an integer. `XSTR', used in the same -fashion, would access it as a string. - -Any operand can be accessed as an integer, as an expression or as a string. -You must choose the correct method of access for the kind of value actually -stored in the operand. You would do this based on the expression code of -the containing expression. That is also how you would know how many -operands there are. - -For example, if X is a `subreg' expression, you know that it has -two operands which can be correctly accessed as `XEXP (x, 0)' and -`XINT (x, 1)'. If you did `XINT (x, 0)', you would get the -address of the expression operand but cast as an integer; that might -occasionally be useful, but it would be cleaner to write `(int) XEXP -(x, 0)'. `XEXP (x, 1)' would also compile without error, and would -return the second, integer operand cast as an expression pointer, which -would probably result in a crash when accessed. Nothing stops you from -writing `XEXP (x, 28)' either, but this will access memory past the -end of the expression with unpredictable results. - -Access to operands which are vectors is more complicated. You can use the -macro `XVEC' to get the vector-pointer itself, or the macros -`XVECEXP' and `XVECLEN' to access the elements and length of a -vector. - -`XVEC (EXP, IDX)' - Access the vector-pointer which is operand number IDX in EXP. - -`XVECLEN (EXP, IDX)' - Access the length (number of elements) in the vector which is - in operand number IDX in EXP. This value is an `int'. - -`XVECLEN (EXP, IDX, ELTNUM)' - Access element number ELTNUM in the vector which is - in operand number IDX in EXP. This value is an `rtx'. - - It is up to you to make sure that ELTNUM is not negative - and is less than `XVECLEN (EXP, IDX)'. - -All the macros defined in this section expand into lvalues and therefore -can be used to assign the operands, lengths and vector elements as well as -to access them. + `tm-sun2.h' + for Sun 2 machines. - -File: internals Node: Machine Modes, Prev: Accessors, Up: RTL, Next: Constants + `tm-3b1.h' + for AT&T 3b1 (aka 7300 Unix PC). -Machine Modes -============= + `tm-isi68.h' + for Integrated Solutions systems. -A machine mode describes a size of data object and the representation used -for it. In the C code, machine modes are represented by an enumeration -type, `enum machine_mode'. Each rtl expression has room for a machine -mode and so do certain kinds of tree expressions (declarations and types, -to be precise). - -In debugging dumps and machine descriptions, the machine mode of an RTL -expression is written after the expression code with a colon to separate -them. The letters `mode' which appear at the end of each machine mode -name are omitted. For example, `(reg:SI 38)' is a `reg' -expression with machine mode `SImode'. If the mode is -`VOIDmode', it is not written at all. - -Here is a table of machine modes. - -`QImode' - "Quarter-Integer" mode represents a single byte treated as an integer. - -`HImode' - "Half-Integer" mode represents a two-byte integer. - -`SImode' - "Single Integer" mode represents a four-byte integer. - -`DImode' - "Double Integer" mode represents an eight-byte integer. - -`TImode' - "Tetra Integer" (?) mode represents a sixteen-byte integer. - -`SFmode' - "Single Floating" mode represents a single-precision (four byte) floating - point number. - -`DFmode' - "Double Floating" mode represents a double-precision (eight byte) floating - point number. - -`TFmode' - "Tetra Floating" mode represents a quadruple-precision (sixteen byte) - floating point number. - -`BLKmode' - "Block" mode represents values that are aggregates to which none of - the other modes apply. In rtl, only memory references can have this mode, - and only if they appear in string-move or vector instructions. On machines - which have no such instructions, `BLKmode' will not appear in RTL. - -`VOIDmode' - Void mode means the absence of a mode or an unspecified mode. - For example, RTL expresslons of code `const_int' have mode - `VOIDmode' because they can be taken to have whatever mode the context - requires. In debugging dumps of RTL, `VOIDmode' is expressed by - the absence of any mode. - -`EPmode' - "Entry Pointer" mode is intended to be used for function variables in - Pascal and other block structured languages. Such values contain - both a function address and a static chain pointer for access to - automatic variables of outer levels. This mode is only partially - implemented since C does not use it. - -`CSImode, ...' - "Complex Single Integer" mode stands for a complex number represented - as a pair of `SImode' integers. Any of the integer and floating modes - may have `C' prefixed to its name to obtain a complex number mode. - For example, there are `CQImode', `CSFmode', and `CDFmode'. - Since C does not support complex numbers, these machine modes are only - partially implemented. - -`BImode' - This is the machine mode of a bit-field in a structure. It is used - only in the syntax tree, never in RTL, and in the syntax tree it appears - only in declaration nodes. In C, it appears only in `FIELD_DECL' - nodes for structure fields defined with a bit size. - -The machine description defines `Pmode' as a C macro which expands -into the machine mode used for addresses. Normally this is `SImode'. - -The only modes which a machine description must support are -`QImode', `SImode', `SFmode' and `DFmode'. The -compiler will attempt to use `DImode' for two-word structures and -unions, but it would not be hard to program it to avoid this. Likewise, -you can arrange for the C type `short int' to avoid using -`HImode'. In the long term it would be desirable to make the set of -available machine modes machine-dependent and eliminate all assumptions -about specific machine modes or their uses from the machine-independent -code of the compiler. - -Here are some C macros that relate to machine modes: - -`GET_MODE (X)' - Returns the machine mode of the rtx X. - -`PUT_MODE (X, NEWMODE)' - Alters the machine mode of the rtx X to be NEWMODE. - -`GET_MODE_SIZE (M)' - Returns the size in bytes of a datum of mode M. - -`GET_MODE_BITSIZE (M)' - Returns the size in bits of a datum of mode M. - -`GET_MODE_UNIT_SIZE (M)' - Returns the size in bits of the subunits of a datum of mode M. - This is the same as `GET_MODE_SIZE' except in the case of - complex modes and `EPmode'. For them, the unit size ithe - size of the real or imaginary part, or the size of the function - pointer or the context pointer. + `tm-news800.h' + for SONY News systems. - -File: internals Node: Constants, Prev: Machine Modes, Up: RTL, Next: Regs and Memory + `tm-hp9k320.h' + for HPUX systems, if you are using GNU CC with the + system's assembler and linker. + + `tm-hp9k320g.h' + for HPUX systems, if you are using the GNU assembler, + linker and other utilities. Not all of the pieces of + GNU software needed for this mode of operation are as + yet in distribution; full instructions will appear + here in the future. + + For the vax, use `tm-vax.h' on BSD Unix, `tm-vaxv.h' on + system V, or `tm-vms.h' on VMS. + + For the SPARC (Sun 4), use `tm-sparc.h'. + + For the Motorola 88000, use `tm-m88k.h'. The support for + the 88000 has a few unfinished spots because there was no + way to run the output. Bugs are suspected in handling of + branch-tables and in the function prologue and epilogue. + + For the 80386, don't use `tm-i386.h' directly. Use + `tm-i386v.h' if the target machine is running system V, + `tm-seq386.h' for a Sequent 386 system, or `tm-compaq.h' + for a Compaq. + + For the 32000, use `tm-sequent.h' if you are using a + Sequent machine, or `tm-encore.h' for an Encore machine, or + `tm-gnx.h' if you are using Genix version 3; otherwise, + perhaps `tm-ns32k.h' will work for you. + + Note that Genix has bugs in `alloca' and `malloc'; you must + get the compiled versions of these from GNU Emacs and edit + GNU CC's `Makefile' to use them. + + Note that Encore systems are supported only under BSD. + + * Make a symbolic link named `md' to the machine description + pattern file (its name should be `MACHINE.md'). + + * Make a symbolic link named `aux-output.c' to the output + subroutine file for your machine (its name should be + `output-MACHINE.c'). + + 4. Make sure the Bison parser generator is installed. (This is + unnecessary if the Bison output files `c-parse.tab.c' and + `cexp.c' are more recent than `c-parse.y' and `cexp.y' and you + do not plan to change the `.y' files.) + + Note that if you have an old version of Bison you may get an + error from the line with the `%expect' directive. If so, simply + remove that line from `c-parse.y' and proceed. + + 5. If you are using a Sun, make sure the environment variable + `FLOAT_OPTION' is not set. If this option were set to `f68881' + when `gnulib' is compiled, the resulting code would demand to be + linked with a special startup file and will not link properly + without special pains. + + 6. Build the compiler. Just type `make' in the compiler directory. + + 7. Move the first-stage object files and executables into a + subdirectory with this command: + + make stage1 + + The files are moved into a subdirectory named `stage1'. Once + installation is complete, you may wish to delete these files + with `rm -r stage1'. + + 8. Recompile the compiler with itself, with this command: -Constant Expression Types -========================= + make CC=stage1/gcc CFLAGS="-g -O -Bstage1/" -The simplest RTL expressions are those that represent constant values. + On a 68000 or 68020 system lacking floating point hardware, + unless you have selected a `tm.h' file that expects by default + that there is no such hardware, do this instead: + + make CC=stage1/gcc CFLAGS="-g -O -Bstage1/ -msoft-float" + + 9. If you wish to test the compiler by compiling it with itself one + more time, do this: + + make stage2 + Make CC=stage2/gcc CFLAGS="-g -O -Bstage2/" + foreach file (*.o) + cmp $file stage2/$file + end + + This will notify you if any of these stage 3 object files + differs from those of stage 2. Any difference, no matter how + innocuous, indicates that the stage 2 compiler has compiled GNU + CC incorrectly, and is therefore a potentially serious bug which + you should investigate and report (*note Bugs::.). + + Aside from the `-B' option, the options should be the same as + when you made stage 2. + + 10. Install the compiler driver, the compiler's passes and run-time + support. You can use the following command: + + make install + + This copies the files `cc1', `cpp' and `gnulib' to files + `gcc-cc1', `gcc-cpp' and `gcc-gnulib' in directory + `/usr/local/lib', which is where the compiler driver program + looks for them. It also copies the driver program `gcc' into + the directory `/usr/local', so that it appears in typical + execution search paths. + + *Warning: there is a bug in `alloca' in the Sun library. To + avoid this bug, install the binaries of GNU CC that were + compiled by GNU CC. They use `alloca' as a built-in function + and never the one in the library.* + + *Warning: the GNU CPP may not work for `ioctl.h', `ttychars.h' + and other system header files unless the `-traditional' option + is used.* The bug is in the header files: at least on some + machines, they rely on behavior that is incompatible with ANSI + C. This behavior consists of substituting for macro argument + names when they appear inside of character constants. The + `-traditional' option tells GNU CC to behave the way these + headers expect. + + Because of this problem, you might prefer to configure GNU CC to + use the system's own C preprocessor. To do so, make the file + `/usr/local/lib/gcc-cpp' a link to `/lib/cpp'. + + Alternatively, on Sun systems and 4.3BSD at least, you can + correct the include files by running the shell script + `fixincludes'. This installs modified, corrected copies of the + files `ioctl.h', `ttychars.h' and many others, in a special + directory where only GNU CC will normally look for them. + + See the file `fixincludes' for a list of all the files we know + to require correction. + +If you cannot install the compiler's passes and run-time support in +`/usr/local/lib', you can alternatively use the `-B' option to +specify a prefix by which they may be found. The compiler +concatenates the prefix with the names `cpp', `cc1' and `gnulib'. +Thus, you can put the files in a directory `/usr/foo/gcc' and specify +`-B/usr/foo/gcc/' when you run GNU CC. + +Also, you can specify an alternative default directory for these +files by setting the Make variable `libdir' when you make GNU CC. -`(const_int I)' - This type of expression represents the integer value I. I - is customarily accessed with the macro `INTVAL' as in - `INTVAL (exp)', which is equivalent to `XINT (exp, 0)'. - - There is only one expression object for the integer value zero; - it is the value of the variable `const0_rtx'. Likewise, the - only expression for integer value one is found in `const1_rtx'. - Any attempt to create an expression of code `const_int' and - value zero or one will return `const0_rtx' or `const1_rtx' - as appropriate. - -`(const_double:M I0 I1)' - Represents a floating point constant value of mode M. The two - integers I0 and I1 together contain the bits of a - `double' value. To convert them to a `double', do - - union { double d; int i[2];} u; - u.i[0] = XINT (x, 0); - u.i[1] = XINT (x, 1); - - and then refer to `u.d'. The value of the constant is - represented as a double in this fashion even if the value represented - is single-precision. - - `dconst0_rtx' and `fconst0_rtx' are `CONST_DOUBLE' - expressions with value 0 and modes `DFmode' and `SFmode'. - -`(symbol_ref SYMBOL)' - Represents the value of an assembler label for data. SYMBOL is - a string that describes the name of the assembler label. If it starts - with a `*', the label is the rest of SYMBOL not including - the `*'. Otherwise, the label is SYMBOL, prefixed with - `_'. - -`(label_ref LABEL)' - Represents the value of an assembler label for code. It contains one - operand, an expression, which must be a `code_label' that appears - in the instruction sequence to identify the place where the label - should go. - - The reason for using a distinct expression type for code label - references is so that jump optimization can distinguish them. - -`(const EXP)' - Represents a constant that is the result of an assembly-time - arithmetic computation. The operand, EXP, is an expression that - contains only constants (`const_int', `symbol_ref' and - `label_ref' expressions) combined with `plus' and - `minus'. However, not all combinations are valid, since the - assembler cannot do arbitrary arithmetic on relocatable symbols.  -File: internals Node: Regs and Memory, Prev: Constants, Up: RTL, Next: Arithmetic +File: internals, Node: VMS Install, Prev: Installation, Up: Installation + +Installing GNU CC on VMS +======================== + +The VMS version of GNU CC is distributed in an unusual tape format +which consists of several tape files. The first is a command file; +the second is an executable program which reads Unix tar format; the +third is another command file which uses this program to read the +remainder of the tape. + +To load the tape, it suffices to mount it `/foreign' and then do +`@mta0:' to execute the command file at the beginning of the tape. + +The tape contains executables and object files as well as sources, so +no compilation is necessary unless you change the sources. (This is +a good thing, since you probably don't have any other C compiler.) +If you must recompile, here is how: + + 1. Copy the file `tm-vms.h' to `tm.h', `config-vms.h' to + `config.h', `vax.md' to `md.' and `output-vax.c' to + `aux-output.c'. + + 2. Type `@make' to do recompile everything. -Registers and Memory -==================== +To install the `GCC' command so you can use the compiler easily, in +the same manner as you use the VMS C compiler, you must install the +VMS CLD file for GNU CC as follows: -Here are the RTL expression types for describing access to machine -registers and to main memory. + 1. Define the VMS logical names `GNU_CC' and `GNU_CC_INCLUDE' to + point to the directories where the GNU CC executables + (`gcc-cpp', `gcc-cc1', etc.) and the C include files are kept. + This should be done with the commands: + + $ assign /super /system disk:[gcc] gnu_cc + $ assign /super /system disk:[gcc.include] gnu_cc_include + + with the appropriate disk and directory names. These commands + can be placed in your system startup file so they will be + executed whenever the machine is rebooted. + + 2. Install the `GCC' command with the command line: + + $ set command /table=sys$library:dcltables gnu_cc:gcc + + Now you can invoke the compiler with a command like `gcc + /verbose file.c', which is equivalent to the command `gcc -v -c + file.c' in Unix. -`(reg:M N)' - For small values of the integer N (less than - `FIRST_PSEUDO_REGISTER'), this stands for a reference to machine - register number N: a "hard register". For larger values of - N, it stands for a temporary value or "pseudo register". - The compiler's strategy is to generate code assuming an unlimited - number of such pseudo registers, and later convert them into hard - registers or into memory references. - - The symbol `FIRST_PSEUDO_REGISTER' is defined by the machine - description, since the number of hard registers on the machine is an - invariant characteristic of the machine. Note, however, that not - all of the machine registers must be general registers. All the - machine registers that can be used for storage of data are given - hard register numbers, even those that can be used only in certain - instructions or can hold only certain types of data. - - Each pseudo register number used in a function's rtl code is - represented by a unique `reg' expression. - - M is the machine mode of the reference. It is necessary because - machines can generally refer to each register in more than one mode. - For example, a register may contain a full word but there may be - instructions to refer to it as a half word or as a single byte, as - well as instructions to refer to it as a floating point number of - various precisions. - - Even for a register that the machine can access in only one mode, - the mode must always be specified. - - A hard register may be accessed in various modes throughout one - function, but each pseudo register is given a natural mode - and is accessed only in that mode. When it is necessary to describe - an access to a pseudo register using a nonnatural mode, a `subreg' - expression is used. - - A `reg' expression with a machine mode that specifies more than - one word of data may actually stand for several consecutive registers. - If in addition the register number specifies a hardware register, then - it actually represents several consecutive hardware registers starting - with the specified one. - - Such multi-word hardware register `reg' expressions may not be live - across the boundary of a basic block. The lifetime analysis pass does not - know how to record properly that several consecutive registers are - actually live there, and therefore register allocation would be confused. - The CSE pass must go out of its way to make sure the situation does - not arise. - -`(subreg:M REG WORDNUM)' - `subreg' expressions are used to refer to a register in a machine - mode other than its natural one, or to refer to one register of - a multi-word `reg' that actually refers to several registers. - - Each pseudo-register has a natural mode. If it is necessary to - operate on it in a different mode---for example, to perform a fullword - move instruction on a pseudo-register that contains a single byte--- - the pseudo-register must be enclosed in a `subreg'. In such - a case, WORDNUM is zero. - - The other use of `subreg' is to extract the individual registers - of a multi-register value. Machine modes such as `DImode' and - `EPmode' indicate values longer than a word, values which usually - require two consecutive registers. To access one of the registers, - use a `subreg' with mode `SImode' and a WORDNUM that - says which register. - - The compilation parameter `WORDS_BIG_ENDIAN', if defined, says - that word number zero is the most significant part; otherwise, it is - the least significant part. - - Note that it is not valid to access a `DFmode' value in `SFmode' - using a `subreg'. On some machines the most significant part of a - `DFmode' value does not have the same format as a single-precision - floating value. - -`(cc0)' - This refers to the machine's condition code register. It has no - operands and may not have a machine mode. It may be validly used in - only two contexts: as the destination of an assignment (in test and - compare instructions) and in comparison operators comparing against - zero (`const_int' with value zero; that is to say, - `const0_rtx'. - - There is only one expression object of code `cc0'; it is the - value of the variable `cc0_rtx'. Any attempt to create an - expression of code `cc0' will return `cc0_rtx'. - - One special thing about the condition code register is that instructions - can set it implicitly. On many machines, nearly all instructions set - the condition code based on the value that they compute or store. - It is not necessary to record these actions explicitly in the RTL - because the machine description includes a prescription for recognizing - the instructions that do so (by means of the macro `NOTICE_UPDATE_CC'). - Only instructions whose sole purpose is to set the condition code, - and instructions that use the condition code, need mention `(cc0)'. - -`(pc)' - This represents the machine's program counter. It has no operands and - may not have a machine mode. `(pc)' may be validly used only in - certain specific contexts in jump instructions. - - There is only one expression object of code `pc'; it is the value of - the variable `pc_rtx'. Any attempt to create an expression of code - `pc' will return `pc_rtx'. - - All instructions that do not jump alter the program counter implicitly, - but there is no need to mention this in the RTL. - -`(mem:M ADDR)' - This rtx represents a reference to main memory at an address - represented by the expression ADDR. M specifies how - large a unit of memory is accessed.  -File: internals Node: Arithmetic, Prev: Regs and Memory, Up: RTL, Next: Comparisons +File: internals, Node: Trouble, Next: Incompatibilities, Prev: Installation, Up: Top + +Trouble in Installation +*********************** + +Here are some of the things that have caused trouble for people +installing GNU CC. -RTL Expressions for Arithmetic -============================== + * On certain systems, defining certain environment variables such + as `CC' can interfere with the functioning of `make'. + + * Cross compilation can run into trouble for certain machines + because some target machines' assemblers require floating point + numbers to be written as *integer* constants in certain contexts. + + The compiler writes these integer constants by examining the + floating point value as an integer and printing that integer, + because this is simple to write and independent of the details + of the floating point representation. But this does not work if + the compiler is running on a different machine with an + incompatible floating point format, or even a different + byte-ordering. + + It is possible to fix this by writing machine-independent code + which understands the floating point representation of the + target machine. I am not interested in doing that much work to + compensate for bugs in assemblers. -`(plus:M X Y)' - Represents the sum of the values represented by X and Y - carried out in machine mode M. This is valid only if - X and Y both are valid for mode M. - -`(minus:M X Y)' - Like `plus' but represents subtraction. - -`(minus X Y)' - Represents the result of subtracting Y from X - for purposes of comparison. The absence of a machine mode - in the `minus' expression indicates that the result is - computed without overflow, as if with infinite precision. - - Of course, machines can't really subtract with infinite precision. - However, they can pretend to do so when only the sign of the - result will be used, which is the case when the result is stored - in `(cc0)'. And that is the only was this kind of expression - may validly be used: as a value to be stored in the condition codes. - -`(neg:M X)' - Represents the negation (subtraction from zero) of the value - represented by X, carried out in mode M. X must be - valid for mode M. - -`(mult:M X Y)' - Represents the signed product of the values represented by X and - Y carried out in machine mode M. If - X and Y are both valid for mode M, this is ordinary - size-preserving multiplication. Alteratively, both X and Y - may be valid for a different, narrower mode. This represents the - kind of multiplication that generates a product wider than the operands. - Widening multiplication and same-size multiplication are completely - distinct and supported by different machine instructions; machines may - support one but not the other. - - `mult' may be used for floating point division as well. - Then M is a floating point machine mode. - -`(umult:M X Y)' - Like `mult' but represents unsigned multiplication. It may be - used in both same-size and widening forms, like `mult'. - `umult' is used only for fixed-point division. - -`(div:M X Y)' - Represents the quotient in signed division of X by Y, - carried out in machine mode M. If M is a floating-point - mode, it represents the exact quotient; otherwise, the integerized - quotient. If X and Y are both valid for mode M, - this is ordinary size-preserving division. Some machines have - division instructions in which the operands and quotient widths are - not all the same; such instructions are represented by `div' - expressions in which the machine modes are not all the same. - -`(udiv:M X Y)' - Like `div' but represents unsigned division. - -`(mod:M X Y)' -`(umod:M X Y)' - Like `div' and `udiv' but represent the remainder instead of - the quotient. - -`(not:M X)' - Represents the bitwise complement of the value represented by X, - carried out in mode M, which must be a fixed-point machine mode. - X must be valid for mode M, which must be a fixed-point mode. - -`(and:M X Y)' - Represents the bitwise logical-and of the values represented by - X and Y, carried out in machine mode M. This is - valid only if X and Y both are valid for mode M, - which must be a fixed-point mode. - -`(ior:M X Y)' - Represents the bitwise inclusive-or of the values represented by - X and Y, carried out in machine mode M. This is - valid only if X and Y both are valid for mode M, - which must be a fixed-point mode. - -`(xor:M X Y)' - Represents the bitwise exclusive-or of the values represented by - X and Y, carried out in machine mode M. This is - valid only if X and Y both are valid for mode M, - which must be a fixed-point mode. - -`(lshift:M X C)' - Represents the result of logically shifting X left by C - places. X must be valid for the mode M, a fixed-point - machine mode. C must be valid for a fixed-point mode; - which mode is determined by the mode called for in the machine - description entry for the left-shift instruction. For example, - on the Vax, the mode of C is `QImode' regardless of M. - - On some machines, negative values of C may be meaningful; this - is why logical left shift an arithmetic left shift are distinguished. - For example, Vaxes have no right-shift instructions, and right shifts - are represented as left-shift instructions whose counts happen - to be negative constants or else computed (in a previous instruction) - by negation. - -`(ashift:M X C)' - Like `lshift' but for arithmetic left shift. - -`(lshiftrt:M X C)' -`(ashiftrt:M X C)' - Like `lshift' and `ashift' but for right shift. - -`(rotate:M X C)' -`(rotatert:M X C)' - Similar but represent left and right rotate. - -`(abs:M X)' - Represents the absolute value of X, computed in mode M. - X must be valid for M. - -`(sqrt:M X)' - Represents the square root of X, computed in mode M. - X must be valid for M. Most often M will be - a floating point mode. - \ No newline at end of file