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Annotation of 43BSDTahoe/lib/libc/tahoe/fpe/cvtlf.s, revision 1.1.1.1

1.1       root        1: #ifdef LIBC_SCCS
                      2:        .asciz  "@(#)cvtlf.s    1.1 (Berkeley/CCI) 7/2/86"
                      3: #endif LIBC_SCCS
                      4: 
                      5: #include <tahoemath/fp.h>
                      6: #include "DEFS.h"
                      7: 
                      8: XENTRY(cvtlf, R2|R3|R4|R5)
                      9:  #
                     10:  #Some initializations:
                     11:  #
                     12:        clrl    r1
                     13:        clrl    r4              # r4 - negative flag.
                     14:        clrl    r2              # r2 - exponent.
                     15:        movl    4(fp),r0        # fetch operand.
                     16:        movl    r0,r5           # need another copy.
                     17:        jeql    retzero         # return zero.
                     18:        jgtr    positive
                     19:        mnegl   r0,r0
                     20:        jvs     retmin          # return minimum integer.
                     21:        incl    r4              # remember it was negative.
                     22:        movl    r0,r5           # remember the negated value.
                     23:  #
                     24:  #Compute exponent:
                     25:  #
                     26: positive:
                     27:        ffs     r0,r1
                     28:        incl    r1
                     29:        addl2   r1,r2
                     30:        shrl    r1,r0,r0
                     31:        jneq    positive        # look for more set bits.
                     32:  #
                     33:  #we have the exponent in r2.
                     34:  #
                     35:        movl    r5,r0           # r0 will hold the resulting f.p. number.
                     36:  #
                     37:  #Shift the fraction part to its proper place:
                     38:  #
                     39:        subl3   r2,$HID_POS,r3
                     40:        jlss    shiftr          # if less then zero we have to shift right.
                     41:        shll    r3,r0,r0        # else we shift left.
                     42:        jmp     shifted
                     43: shiftr:
                     44:        mnegl   r3,r3
                     45:        shrl    r3,r0,r0
                     46: shifted:
                     47:        andl2   $CLEARHID,r0    # clear the hidden bit.
                     48:        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
                     49:        orl2    $EXPSIGN,r2     # set the exponent sign bit(to bias it).
                     50:        orl2    r2,r0           # combine exponent & fraction.
                     51:        bbc     $0,r4,sign_ok   # do we  have to set the sign bit?
                     52:        orl2    $SIGNBIT,r0     # yes...
                     53: sign_ok:
                     54:        ret
                     55: 
                     56: retzero:
                     57:        clrl    r0
                     58:        ret
                     59: 
                     60: retmin:
                     61:        movl    $0xd0000000,r0
                     62:        ret
                     63: 
                     64: 
                     65:        

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