From: Rémy Oudompheng <oudomphe@phare.normalesup.org>
Date: Tue, 4 Jun 2013 06:33:00 +0000 (+0200)
Subject: cmd/6c, cmd/8c: avoid generating long multiplication when not necessary.
X-Git-Tag: go1.2rc2~1334
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=2c0b00744f067c7d9f44a735f77aa0eb0e2e345e;p=gostls13.git

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

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
---

diff --git a/src/cmd/6c/cgen.c b/src/cmd/6c/cgen.c
index 95400c4453..7afacb2177 100644
--- a/src/cmd/6c/cgen.c
+++ b/src/cmd/6c/cgen.c
@@ -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;
 		}
 
diff --git a/src/cmd/8c/cgen.c b/src/cmd/8c/cgen.c
index 78eb7ecedb..4d4ae13abe 100644
--- a/src/cmd/8c/cgen.c
+++ b/src/cmd/8c/cgen.c
@@ -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;
 		}