cmd/9g: note suboptimal copy code
9g generates needlessly complex code for small copies. There are a
few other things that need to be improved about the copy code, so for
now just note the problem.
Change-Id: I0f1de4b2f9197a2635e27cc4b91ecf7a6c11f457
Reviewed-on: https://go-review.googlesource.com/3665
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/cmd/9g/cgen.c b/src/cmd/9g/cgen.c
index d1f1976..2d76133 100644
--- a/src/cmd/9g/cgen.c
+++ b/src/cmd/9g/cgen.c
@@ -1506,6 +1506,11 @@
patch(gbranch(ABNE, T, 0), ploop);
regfree(&nend);
} else {
+ // TODO(austin): Instead of generating ADD $-8,R8; ADD
+ // $-8,R7; n*(MOVDU 8(R8),R9; MOVDU R9,8(R7);) just
+ // generate the offsets directly and eliminate the
+ // ADDs. That will produce shorter, more
+ // pipeline-able code.
while(c-- > 0) {
p = gins(op, &src, &tmp);
p->from.type = TYPE_MEM;
