From: Cherry Zhang <cherryyz@google.com>
Date: Thu, 15 Apr 2021 03:36:14 +0000 (-0400)
Subject: cmd/compile: in clobberdead mode, don't clobber slots that are live for defers
X-Git-Tag: go1.17beta1~592
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=9fbcba6664;p=gostls13.git

cmd/compile: in clobberdead mode, don't clobber slots that are live for defers

There are stack slots that are kept live for defers, which are
tracked separately. Don't clobber them.

Change-Id: Ib558345758b5a4fd89c7ff8a3fe08087059add21
Reviewed-on: https://go-review.googlesource.com/c/go/+/310329
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
---

diff --git a/src/cmd/compile/internal/liveness/plive.go b/src/cmd/compile/internal/liveness/plive.go
index 53feb6cc32..9eca05b040 100644
--- a/src/cmd/compile/internal/liveness/plive.go
+++ b/src/cmd/compile/internal/liveness/plive.go
@@ -995,9 +995,11 @@ func (lv *liveness) clobber(b *ssa.Block) {
 // of b.Values.
 func clobber(lv *liveness, b *ssa.Block, live bitvec.BitVec) {
 	for i, n := range lv.vars {
-		if !live.Get(int32(i)) && !n.Addrtaken() {
+		if !live.Get(int32(i)) && !n.Addrtaken() && !n.OpenDeferSlot() && !n.IsOutputParamHeapAddr() {
 			// Don't clobber stack objects (address-taken). They are
 			// tracked dynamically.
+			// Also don't clobber slots that are live for defers (see
+			// the code setting livedefer in epilogue).
 			clobberVar(b, n)
 		}
 	}