From: Dave Cheney <dave@cheney.net>
Date: Fri, 21 Dec 2012 22:09:31 +0000 (+1100)
Subject: cmd/5g: avoid temporaries in agen OINDEX
X-Git-Tag: go1.1rc2~1566
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=3dcc63f750c425fcb9ce2ec66812489881dafeee;p=gostls13.git

cmd/5g: avoid temporaries in agen OINDEX

Most benchmarks are within the 3% margin of error. This code path is quite common in the fmt package.

linux/arm, Freescale iMX.53 (cortex-a8)

fmt:
benchmark                      old ns/op    new ns/op    delta
BenchmarkSprintfEmpty                925          785  -15.14%
BenchmarkSprintfString              5050         5039   -0.22%
BenchmarkSprintfInt                 4425         4406   -0.43%
BenchmarkSprintfIntInt              5802         5762   -0.69%
BenchmarkSprintfPrefixedInt         7029         6541   -6.94%
BenchmarkSprintfFloat              10278        10083   -1.90%
BenchmarkManyArgs                  18558        17606   -5.13%
BenchmarkScanInts               15592690     15415360   -1.14%
BenchmarkScanRecursiveInt       25155020     25050900   -0.41%

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6921056
---

diff --git a/src/cmd/5g/cgen.c b/src/cmd/5g/cgen.c
index 9325741059..e6c92f68f6 100644
--- a/src/cmd/5g/cgen.c
+++ b/src/cmd/5g/cgen.c
@@ -1007,22 +1007,21 @@ agenr(Node *n, Node *a, Node *res)
 
 		if(!debug['B'] && !n->bounded) {
 			// check bounds
-			regalloc(&n4, types[TUINT32], N);
 			if(isconst(nl, CTSTR)) {
-				nodconst(&n1, types[TUINT32], nl->val.u.sval->len);
-				gmove(&n1, &n4);
+				nodconst(&n4, types[TUINT32], nl->val.u.sval->len);
 			} else if(isslice(nl->type) || nl->type->etype == TSTRING) {
 				n1 = n3;
 				n1.op = OINDREG;
 				n1.type = types[tptr];
 				n1.xoffset = Array_nel;
+				regalloc(&n4, types[TUINT32], N);
 				gmove(&n1, &n4);
 			} else {
-				nodconst(&n1, types[TUINT32], nl->type->bound);
-				gmove(&n1, &n4);
+				nodconst(&n4, types[TUINT32], nl->type->bound);
 			}
 			gcmp(optoas(OCMP, types[TUINT32]), &n2, &n4);
-			regfree(&n4);
+			if(n4.op == OREGISTER)
+				regfree(&n4);
 			p1 = gbranch(optoas(OLT, types[TUINT32]), T, +1);
 			if(p2)
 				patch(p2, pc);