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cmd/5g: avoid temporary during constant asop

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func add() int {
        var a int
        a += 10
        a += 20
        a += 30
        a -= 10
        a -= 20
        a -= 30
        return a
}

before

--- prog list "add" ---
0000 (/home/dfc/src/add.go:5) TEXT      add+0(SB),$0-4
0001 (/home/dfc/src/add.go:6) MOVW      $0,R2
0002 (/home/dfc/src/add.go:7) MOVW      $10,R0
0003 (/home/dfc/src/add.go:7) ADD       R0,R2,R1
0004 (/home/dfc/src/add.go:8) MOVW      $20,R0
0005 (/home/dfc/src/add.go:8) ADD       R0,R1
0006 (/home/dfc/src/add.go:9) MOVW      $30,R0
0007 (/home/dfc/src/add.go:9) ADD       R0,R1
0008 (/home/dfc/src/add.go:10) MOVW     $10,R0
0009 (/home/dfc/src/add.go:10) SUB      R0,R1
0010 (/home/dfc/src/add.go:11) MOVW     $20,R0
0011 (/home/dfc/src/add.go:11) SUB      R0,R1
0012 (/home/dfc/src/add.go:12) MOVW     $30,R0
0013 (/home/dfc/src/add.go:12) SUB      R0,R1,R2
0014 (/home/dfc/src/add.go:12) MOVW     R2,R0
0015 (/home/dfc/src/add.go:13) MOVW     R2,R1
0016 (/home/dfc/src/add.go:13) MOVW     R2,.noname+0(FP)
0017 (/home/dfc/src/add.go:13) RET      ,

after

--- prog list "add" ---
0000 (/home/dfc/src/add.go:5) TEXT      add+0(SB),$0-4
0001 (/home/dfc/src/add.go:6) MOVW      $0,R0
0002 (/home/dfc/src/add.go:7) ADD       $10,R0
0003 (/home/dfc/src/add.go:8) ADD       $20,R0
0004 (/home/dfc/src/add.go:9) ADD       $30,R0
0005 (/home/dfc/src/add.go:10) SUB      $10,R0
0006 (/home/dfc/src/add.go:11) SUB      $20,R0
0007 (/home/dfc/src/add.go:12) SUB      $30,R0,R2
0008 (/home/dfc/src/add.go:13) MOVW     R2,R0
0009 (/home/dfc/src/add.go:13) MOVW     R2,.noname+0(FP)
0010 (/home/dfc/src/add.go:13) RET      ,

R=rsc, minux.ma, remyoudompheng
CC=golang-dev
https://golang.org/cl/6584056
This commit is contained in:
Dave Cheney 2012-10-06 21:01:49 +10:00
parent 782464aea5
commit bbccfddb84
1 changed files with 8 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
src/cmd/5g/ggen.c
View File

@ -371,14 +371,19 @@ cgen_asop(Node *n)
case OOR:
a = optoas(n->etype, nl->type);
if(nl->addable) {
regalloc(&n3, nr->type, N);
cgen(nr, &n3);
if(smallintconst(nr))
n3 = *nr;
else {
regalloc(&n3, nr->type, N);
cgen(nr, &n3);
}
regalloc(&n2, nl->type, N);
cgen(nl, &n2);
gins(a, &n3, &n2);
cgen(&n2, nl);
regfree(&n2);
regfree(&n3);
if(n3.op != OLITERAL)
regfree(&n3);
goto ret;
}
if(nr->ullman < UINF)