cmd/compile: ignore types when considering tuple select for CSE

Fixes #20097

Change-Id: I3c9626ccc8cd0c46a7081ea8650b2ff07a5d4fcd
Reviewed-on: https://go-review.googlesource.com/41505
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssa/cse.go b/src/cmd/compile/internal/ssa/cse.go
index d852e22d5c90d83e24b8209896d62a888bcf2ba5..d931d6bf5fd1fcca82f1e3dda1863508e1e54493 100644 (file)
--- a/src/cmd/compile/internal/ssa/cse.go
+++ b/src/cmd/compile/internal/ssa/cse.go
@@ -322,9 +322,13 @@ func cmpVal(v, w *Value, auxIDs auxmap) types.Cmp {
                // that generate memory.
                return lt2Cmp(v.ID < w.ID)
        }
-
-       if tc := v.Type.Compare(w.Type); tc != types.CMPeq {
-               return tc
+       // OpSelect is a pseudo-op. We need to be more agressive
+       // regarding CSE to keep multiple OpSelect's of the same
+       // argument from existing.
+       if v.Op != OpSelect0 && v.Op != OpSelect1 {
+               if tc := v.Type.Compare(w.Type); tc != types.CMPeq {
+                       return tc
+               }
        }
 
        if v.Aux != w.Aux {

diff --git a/test/fixedbugs/issue20097.go b/test/fixedbugs/issue20097.go
new file mode 100644 (file)
index 0000000..236a1bd
--- /dev/null
+++ b/test/fixedbugs/issue20097.go
@@ -0,0 +1,18 @@
+// compile
+
+// Copyright 2017 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 20097: ensure that we CSE multiple Select ops with
+// the same underlying type
+
+package main
+
+type T int64
+
+func f(x, y int64) (int64, T) {
+       a := x / y
+       b := T(x) / T(y)
+       return a, b
+}