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 1b936b8a5f60002f84f271bc217070d3655cd09a..5b282eb2f250423f14a84dda7e3801968ad533db 100644 (file)
--- 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