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cmd/6c: Improve peep hole optimization of rotate and shift instructions.

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Update #4629.

$ cat shift2.c
unsigned int
shift(unsigned int x, unsigned int y)
{
        x = (x << 3);
        y = (y << 5);
        x = (x << 7);
        y = (y << 9);
        return x ^ y;
}

## BEFORE
$ go tool 6c -S shift2.c
(shift2.c:2)	TEXT	shift+0(SB),$0-8
(shift2.c:4)	MOVL	x+0(FP),!!AX
(shift2.c:4)	SALL	$3,!!AX
(shift2.c:4)	MOVL	AX,!!DX
(shift2.c:5)	MOVL	y+4(FP),!!AX
(shift2.c:5)	SALL	$5,!!AX
(shift2.c:5)	MOVL	AX,!!CX
(shift2.c:6)	MOVL	DX,!!AX
(shift2.c:6)	SALL	$7,!!AX
(shift2.c:6)	MOVL	AX,!!DX
(shift2.c:7)	MOVL	CX,!!AX
(shift2.c:7)	SALL	$9,!!AX
(shift2.c:7)	MOVL	AX,!!CX
(shift2.c:8)	MOVL	DX,!!AX
(shift2.c:8)	XORL	CX,!!AX
(shift2.c:8)	RET	,!!
(shift2.c:8)	RET	,!!
(shift2.c:8)	END	,!!

## AFTER
$ go tool 6c -S shift2.c
(shift2.c:2)	TEXT	shift+0(SB),$0-8
(shift2.c:4)	MOVL	x+0(FP),!!AX
(shift2.c:4)	SALL	$3,!!AX
(shift2.c:5)	MOVL	y+4(FP),!!CX
(shift2.c:5)	SALL	$5,!!CX
(shift2.c:6)	SALL	$7,!!AX
(shift2.c:7)	SALL	$9,!!CX
(shift2.c:8)	XORL	CX,!!AX
(shift2.c:8)	RET	,!!
(shift2.c:8)	RET	,!!
(shift2.c:8)	END	,!!

R=rsc, minux.ma, dave, nigeltao
CC=golang-dev
https://golang.org/cl/7066055
This commit is contained in:
Matthew Dempsky 2013-01-18 16:33:25 -05:00 committed by Russ Cox
parent dfdfba14b9
commit 41ec481a53
2 changed files with 22 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/cmd/6c/peep.c
View File

@ -330,20 +330,7 @@ subprop(Reg *r0)
case AIMULW:
if(p->to.type != D_NONE)
break;
case ADIVB:
case ADIVL:
case ADIVQ:
case ADIVW:
case AIDIVB:
case AIDIVL:
case AIDIVQ:
case AIDIVW:
case AIMULB:
case AMULB:
case AMULL:
case AMULQ:
case AMULW:
goto giveup;
case AROLB:
case AROLL:
@ -369,6 +356,23 @@ subprop(Reg *r0)
case ASHRL:
case ASHRQ:
case ASHRW:
if(p->from.type == D_CONST)
break;
goto giveup;
case ADIVB:
case ADIVL:
case ADIVQ:
case ADIVW:
case AIDIVB:
case AIDIVL:
case AIDIVQ:
case AIDIVW:
case AIMULB:
case AMULB:
case AMULL:
case AMULQ:
case AMULW:
case AREP:
case AREPN:
@ -384,6 +388,7 @@ subprop(Reg *r0)
case AMOVSL:
case AMOVSQ:
case AMOVQL:
giveup:
return 0;
case AMOVL:

3
src/cmd/6g/peep.c
View File

@ -664,6 +664,7 @@ subprop(Reg *r0)
case AIMULW:
if(p->to.type != D_NONE)
break;
goto giveup;
case ARCLB:
case ARCLL:
@ -699,6 +700,7 @@ subprop(Reg *r0)
case ASHRW:
if(p->from.type == D_CONST)
break;
goto giveup;
case ADIVB:
case ADIVL:
@ -727,6 +729,7 @@ subprop(Reg *r0)
case AMOVSB:
case AMOVSL:
case AMOVSQ:
giveup:
if(debug['P'] && debug['v'])
print("\tfound %P; return 0\n", p);
return 0;