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1.1 root 1: Copyright (c) 1985 Regents of the University of California.
2: All rights reserved. The Berkeley software License Agreement
3: specifies the terms and conditions for redistribution.
4:
5: @(#)INFO 5.1 (Berkeley) 1/8/86
6:
7: HOW TO INTERPRET TEMPLATES:
8:
9: Goals (represented by 'visit' fields) indicate the shape of what is
10: produced by using a template:
11:
12: Goal Form of result
13:
14: FOREFF Can be used for just side effects. Used for things
15: like initializing data, or gotos.
16: INAREG Result can end up in a register.
17: INTAREG Result can end up in a scratch register.
18: INBREG Result can end up in an index, address or floating
19: point register -- not used on the VAX.
20: INTBREG The same except for temporary index registers.
21: FORCC Condition codes are set.
22: INTEMP Computes into a temporary location.
23: FORARG Computes a function argument onto the stack.
24: FORREW Forces the code generator to rewrite the tree.
25:
26: Shapes are restrictions on operands:
27:
28: Shape Form of operand
29:
30: SANY Anything.
31:
32: SAREG A register.
33: STAREG A temporary register (one that can be stomped on).
34: SBREG A secondary register -- not used on the VAX.
35: STBREG Ditto except this a temporary register.
36:
37: SCON An int (32-bit or smaller) constant.
38: SCCON A short (16-bit) constant.
39: SSCON A char (8-bit) constant.
40: SZERO The constant 0.
41: SONE The constant 1.
42: SMONE The constant -1.
43:
44: SCC Condition codes.
45:
46: SNAME A constant address; not on the stack or indirect
47: through a pointer.
48:
49: SFLD A bit field.
50:
51: SOREG A value whose address is the sum of a register and an
52: offset. E.g. 8(ap).
53: SSOREG A 'simple' OREG: not a pointer (e.g. rules out *8(ap)).
54: SWADD A value with an offset that is larger than a byte.
55: STARNM A value whose address is at some known address.
56: An indirect value. E.g. *_a, *8(ap).
57: STARREG Indirect through a register with auto-increment or
58: -decrement.
59:
60: Types restrict the type of an operand. There are two ways of
61: representing types in the compiler; one is a specific type that
62: indicates things like indirection, and the other is used as a template
63: for the first. To see whether a type matches a template, you call
64: ttype(). The template variety is what you see in code templates, and
65: has its own typedef, TWORD. Here are some things you can ask for in
66: the way of type templates:
67:
68: Name What it buys you
69:
70: TANY Matches anything 'within reason'.
71:
72: TCHAR Chars.
73: TUCHAR Unsigned chars.
74: TSHORT Shorts.
75: TUSHORT Unsigned shorts.
76: TINT Ints.
77: TLONG Longs. (VAX ints.)
78: TULONG Unsigned longs.
79: TUNSIGNED Any unsigned type.
80: TWORD An integral type the size of an int, or a pointer.
81:
82: TFLOAT Floats.
83: TDOUBLE Doubles.
84:
85: TSTRUCT Structures or unions.
86:
87: TPTRTO A pointer. This must be or'ed in with other types;
88: e.g. TPTRTO|TFLOAT|TDOUBLE matches pointers to floats
89: or pointers to doubles. Can be multiply indirect.
90: TPOINT Complex types -- things with stars or brackets or etc.
91:
92: WPTR Pointer to anything except structures/unions.
93: ANYSIGNED Pointers or signed integral types.
94: ANYUSIGNED Any unsigned integral type.
95: ANYFIXED Any integral type (excludes floating point or structs).
96:
97: The template may request special resources. These are indicated by
98: things in the needs field of a template:
99:
100: Needs Resource wanted
101:
102: NAREG Needs a register. Can be multiplied up to 4 times
103: to get up to 4 registers.
104: NBREG Ditto for secondary registers (not used on the VAX).
105: NASL Can share a register with the left operand.
106: NASR Can share a register with the right operand.
107: NTEMP Needs stack space. Can be multiplied up to 8 times.
108: EITHER Don't settle for some of A and some of B.
109:
110: The template indicates where the results end up, too. The symbols in the
111: rewrite field have the following meanings:
112:
113: Result Where the result is
114:
115: RNULL Don't care about the result -- clobber it.
116: RLEFT Register associated with the left operand.
117: RRIGHT Register associated with the right operand.
118: RESC1 First register requested by 'needs'.
119: RESC2 Second register requested by 'needs'.
120: RESC3 Third register requested by 'needs'.
121: RESCC The condition codes.
122: RNOP Doesn't make anything -- e.g. initializations, gotos.
123:
124: The assembly language templates contain capital letter abbreviations
125: which are expanded in context to whatever is useful. These
126: abbreviations may be 1, 2 or 3 characters long; the first character
127: codes for the length and generally tells what to do. A standard second
128: or third character often indicates the location of an object in the
129: following way:
130:
131: Modifier Meaning
132:
133: L Left operand.
134: R Right operand
135: 1, 2, 3 Nth requested register (from 'needs').
136:
137: Below are the various abbreviations; 'n' is used to indicate one of the
138: standard modifiers:
139:
140: Abbreviation Rewrites as
141:
142: An Address of operand n -- the most common abbreviation.
143: Produces register names, externals, almost everything.
144: Bn Byte offset in a word (? -- not used on VAX).
145: Cn Only constants may be written this way.
146: F The rest of the line is ignored if this value is
147: only being computed for side effects.
148: H Field shift; used with masks and bit fields.
149: In Illegal -- not currently used.
150: L A label.
151: M Field mask.
152: N Field mask, complemented.
153: O[BWLFD] Opcode string; used to rewrite operands of templates
154: with generic opcodes like add, sub, mul. The modifier
155: is changed to lower case and appended. For example if
156: the template is OPFLOAT, the abbreviation is 'OD2' and
157: the current node's operand is OPMUL, you get 'muld2'.
158: S Field size.
159: T Rewriting of the register type is suppressed. I'm not
160: sure what's going on but here's the explanation: 'The C
161: language requires intermediate results to change type.
162: This is inefficient or impossible on some machines; the
163: "T" command in match supresses this type changing.'
164: Un Illegal -- not currently used.
165: Zx Local abbreviations (zzzcode()). The x's are spelled
166: out below:
167: ZA Used for straightforward conversions and assignments.
168: Clever perhaps to excess in its coding.
169: ZB Gets difficult shapes into register prior to a shift.
170: ZC Interpolates the argument count in a function call.
171: ZD Get the value of the operand, then increment or
172: decrement the original, depending on the opcode.
173: ZE Increment or decrement the operand.
174: ZF Produces 'd', 'f' or 'l' depending on whether the
175: right operand (the node itself, for unary operators)
176: is double, float or long; used for moves into register.
177: ZI Produces the appropriate conditional branch.
178: ZL Opcode type [bwlfd] for the left operand.
179: ZN Produces a jump and a clear to get logical values
180: converted into 0 or 1.
181: ZP Just like ZI.
182: ZR Opcode type [bwlfd] for the right operand.
183: ZS Generates a structure assignment.
184: ZT Rounds up structure lengths for struct arguments.
185: ZU Subtracts the value of the constant right operand from
186: 32 and uses that for unsigned right shift offsets.
187: ZZ Complements the value of the constant right operand of
188: a bit instruction and produces it.
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