From: Austin Clements <austin@google.com>
Date: Fri, 30 Jan 2015 16:18:24 +0000 (-0500)
Subject: cmd/9g: note suboptimal copy code
X-Git-Tag: go1.5beta1~2182
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=36f879780aa086356187a7ca8a625ff37484d317;p=gostls13.git

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 d1f1976ce8..2d76133543 100644
--- a/src/cmd/9g/cgen.c
+++ b/src/cmd/9g/cgen.c
@@ -1506,6 +1506,11 @@ sgen(Node *n, Node *ns, int64 w)
 		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;