cmd/compile: fix scheduling of memory-producing tuple ops

Intrinsified atomic op produces <value,memory>. Make sure this
memory is considered in the store chain calculation.

Fixes #16948.

Change-Id: I029f164b123a7e830214297f8373f06ea0bf1e26
Reviewed-on: https://go-review.googlesource.com/28350
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssa/schedule.go b/src/cmd/compile/internal/ssa/schedule.go
index bf3fb27f905e794112ef50f0c7eec8c860729917..ffc816b00ff9ad966137999045716f36c9753937 100644 (file)
--- a/src/cmd/compile/internal/ssa/schedule.go
+++ b/src/cmd/compile/internal/ssa/schedule.go
@@ -128,9 +128,13 @@ func schedule(f *Func) {
                // the calculated store chain is good only for this block.
                for _, v := range b.Values {
                        if v.Op != OpPhi && v.Type.IsMemory() {
+                               mem := v
+                               if v.Op == OpSelect1 {
+                                       v = v.Args[0]
+                               }
                                for _, w := range v.Args {
                                        if w.Type.IsMemory() {
-                                               nextMem[w.ID] = v
+                                               nextMem[w.ID] = mem
                                        }
                                }
                        }

diff --git a/test/fixedbugs/issue16948.go b/test/fixedbugs/issue16948.go
new file mode 100644 (file)
index 0000000..c986024
--- /dev/null
+++ b/test/fixedbugs/issue16948.go
@@ -0,0 +1,34 @@
+// run
+
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// issue 16948: make sure intrinsified atomic ops won't
+// confuse the scheduler.
+
+package main
+
+import "sync/atomic"
+
+func main() {
+       f()
+}
+
+var x int32
+
+type T [10]int
+var sink *T
+
+func f() (t T) {
+       atomic.AddInt32(&x, 1)
+       g(42, 42, 42, 42, 42, &t) // use int values that is invalid pointer to smash the stack slot of return value of runtime.newobject
+       return
+}
+
+//go:noinline
+func g(a, b, c, d, e int, p *T) {
+       var t [10000]int // a large stack frame to trigger stack growing
+       _ = t
+       sink = p // force p (in caller) heap allocated
+}