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deal properly (i hope!) with registers' upper 32 bits, when doing 

32-bit division and remainder.  Sometimes, when optimizing, they could
have been different than previously expected (and could have caused
hokey results).
This commit is contained in:
cgd 1995-09-30 03:09:07 +00:00
parent 2940a41ce2
commit 7a8e7b22a1
1 changed files with 28 additions and 15 deletions
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43
lib/libc/arch/alpha/gen/divrem.m4
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@ -1,4 +1,4 @@
/* $NetBSD: divrem.m4,v 1.4 1995/09/30 02:14:17 cgd Exp $ */
/* $NetBSD: divrem.m4,v 1.5 1995/09/30 03:09:07 cgd Exp $ */
/*
* Copyright (c) 1994, 1995 Carnegie-Mellon University.
@ -52,7 +52,7 @@ define(BIT, `t0')
define(I, `t1')
define(CC, `t2')
define(T_0, `t3')
ifelse(S, `true', `define(SIGN, `t4')')
ifelse(S, `true', `define(NEG, `t4')')
#include "DEFS.h"
@ -63,7 +63,7 @@ LEAF(NAME, 0) /* XXX */
stq CC, 16(sp)
stq T_0, 24(sp)
ifelse(S, `true',
` stq SIGN, 32(sp)')
` stq NEG, 32(sp)')
stq A, 40(sp)
stq B, 48(sp)
mov zero, RESULT /* Initialize result to zero */
@ -71,30 +71,43 @@ ifelse(S, `true',
ifelse(S, `true',
`
/* Compute sign of result. If either is negative, this is easy. */
or A, B, SIGN /* not the sign, but... */
bgt SIGN, Ldoit /* neither negative? do it! */
or A, B, NEG /* not the sign, but... */
srl NEG, WORDSIZE - 1, NEG /* rather, or of high bits */
blbc NEG, Ldoit /* neither negative? do it! */
ifelse(OP, `div',
` xor A, B, SIGN /* THIS is the sign! */
', ` mov A, SIGN /* sign follows A. */
` xor A, B, NEG /* THIS is the sign! */
', ` mov A, NEG /* sign follows A. */
')
bge A, LnegB /* see if A is negative */
srl NEG, WORDSIZE - 1, NEG /* make negation the low bit. */
srl A, WORDSIZE - 1, I /* is A negative? */
blbc I, LnegB /* no. */
/* A is negative; flip it. */
ifelse(WORDSIZE, `32', `
/* top 32 bits may be random junk */
zap A, 0xf0, A
')
subq zero, A, A
bge B, Ldoit /* see if B is negative */
srl B, WORDSIZE - 1, I /* is B negative? */
blbc I, Ldoit /* no. */
LnegB:
/* B is definitely negative, no matter how we got here. */
ifelse(WORDSIZE, `32', `
/* top 32 bits may be random junk */
zap B, 0xf0, B
')
subq zero, B, B
Ldoit:
', `
')
ifelse(WORDSIZE, `32', `
/*
* Clear the top 32 bits of each operand, as the compiler may
* have sign extended them, if the 31st bit was set.
* Clear the top 32 bits of each operand, as they may
* sign extension (if negated above), or random junk.
*/
zap A, 0xf0, A
zap B, 0xf0, B
')' )
')
/* kill the special cases. */
beq B, Ldotrap /* division by zero! */
@ -159,7 +172,7 @@ ifelse(S, `true',
`
/* Check to see if we should negate it. */
subqv zero, RESULT, T_0
cmovlt SIGN, T_0, RESULT
cmovlbs NEG, T_0, RESULT
')
ldq BIT, 0(sp)
@ -167,7 +180,7 @@ ifelse(S, `true',
ldq CC, 16(sp)
ldq T_0, 24(sp)
ifelse(S, `true',
` ldq SIGN, 32(sp)')
` ldq NEG, 32(sp)')
ldq A, 40(sp)
ldq B, 48(sp)
lda sp, 64(sp)