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cmd/6c, cmd/8c: avoid generating long multiplication when not necessary.

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On amd64
benchmark                        old ns/op    new ns/op    delta
BenchmarkHashStringSpeed                91           74  -18.49%
BenchmarkHashInt32Speed                 54           45  -17.88%
BenchmarkHashInt64Speed                 76           58  -23.53%
BenchmarkHashStringArraySpeed          231          188  -18.61%

Fixes #5367.

R=golang-dev, iant, dave, daniel.morsing, ality, rsc
CC=golang-dev
https://golang.org/cl/9040043
This commit is contained in:
Rémy Oudompheng 2013-06-04 08:33:00 +02:00
parent 62891fb811
commit 2c0b00744f
2 changed files with 6 additions and 4 deletions
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5
src/cmd/6c/cgen.c
View File

@ -392,13 +392,13 @@ cgen(Node *n, Node *nn)
}
}
if(o == OMUL) {
if(o == OMUL || o == OLMUL) {
if(l->addable >= INDEXED) {
t = l;
l = r;
r = t;
}
/* should favour AX */
reg[D_DX]++; // for gopcode case OMUL
regalloc(&nod, l, nn);
cgen(l, &nod);
if(r->addable < INDEXED || hardconst(r)) {
@ -410,6 +410,7 @@ cgen(Node *n, Node *nn)
gopcode(OMUL, n->type, r, &nod); /* addressible */
gmove(&nod, nn);
regfree(&nod);
reg[D_DX]--;
break;
}

5
src/cmd/8c/cgen.c
View File

@ -404,13 +404,13 @@ cgen(Node *n, Node *nn)
}
}
if(o == OMUL) {
if(o == OMUL || o == OLMUL) {
if(l->addable >= INDEXED) {
t = l;
l = r;
r = t;
}
/* should favour AX */
reg[D_DX]++; // for gopcode case OMUL
regalloc(&nod, l, nn);
cgen(l, &nod);
if(r->addable < INDEXED) {
@ -422,6 +422,7 @@ cgen(Node *n, Node *nn)
gopcode(OMUL, n->type, r, &nod); /* addressible */
gmove(&nod, nn);
regfree(&nod);
reg[D_DX]--;
break;
}