From: Dave Cheney <dave@cheney.net>
Date: Tue, 11 Aug 2015 21:55:01 +0000 (+1000)
Subject: cmd/compile/internal/ppc64: disable DUFFZERO
X-Git-Tag: go1.5~1^2~21
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=cda1fc0071140c5eb8f71b8eef0da0a39c69b641;p=gostls13.git

cmd/compile/internal/ppc64: disable DUFFZERO

Update #12108

If DUFFZERO is used within a tail call method it will overwrite the
link register.

Change-Id: I6abd2fde0f0ad909ccd55eb119b992673a74f0e2
Reviewed-on: https://go-review.googlesource.com/13570
Reviewed-by: Russ Cox <rsc@golang.org>
---

diff --git a/src/cmd/compile/internal/ppc64/ggen.go b/src/cmd/compile/internal/ppc64/ggen.go
index 1b936b8a5f..5b282eb2f2 100644
--- a/src/cmd/compile/internal/ppc64/ggen.go
+++ b/src/cmd/compile/internal/ppc64/ggen.go
@@ -71,7 +71,10 @@ func zerorange(p *obj.Prog, frame int64, lo int64, hi int64) *obj.Prog {
 		for i := int64(0); i < cnt; i += int64(gc.Widthptr) {
 			p = appendpp(p, ppc64.AMOVD, obj.TYPE_REG, ppc64.REGZERO, 0, obj.TYPE_MEM, ppc64.REGSP, 8+frame+lo+i)
 		}
-	} else if cnt <= int64(128*gc.Widthptr) {
+		// TODO(dfc): https://golang.org/issue/12108
+		// If DUFFZERO is used inside a tail call (see genwrapper) it will
+		// overwrite the link register.
+	} else if false && cnt <= int64(128*gc.Widthptr) {
 		p = appendpp(p, ppc64.AADD, obj.TYPE_CONST, 0, 8+frame+lo-8, obj.TYPE_REG, ppc64.REGRT1, 0)
 		p.Reg = ppc64.REGSP
 		p = appendpp(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_MEM, 0, 0)
@@ -442,7 +445,10 @@ func clearfat(nl *gc.Node) {
 
 		// The loop leaves R3 on the last zeroed dword
 		boff = 8
-	} else if q >= 4 {
+		// TODO(dfc): https://golang.org/issue/12108
+		// If DUFFZERO is used inside a tail call (see genwrapper) it will
+		// overwrite the link register.
+	} else if false && q >= 4 {
 		p := gins(ppc64.ASUB, nil, &dst)
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = 8