[dev.ssa] cmd/compile: handle phi control values

Tests courtesy of Todd Neal.

Change-Id: If657c7c7d3cd1ce01e9d9ad79eb6b2110230c0f9
Reviewed-on: https://go-review.googlesource.com/13267
Reviewed-by: Todd Neal <todd@tneal.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/gc/testdata/ctl_ssa.go

@@ -0,0 +1,53 @@
+// run
+
+// Copyright 2015 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.
+
+// Test control flow
+
+package main
+
+// nor_ssa calculates NOR(a, b).
+// It is implemented in a way that generates
+// phi control values.
+func nor_ssa(a, b bool) bool {
+	var c bool
+	if a {
+		c = true
+	}
+	if b {
+		c = true
+	}
+	if c {
+		return false
+	}
+	return true
+}
+
+func testPhiControl() {
+	tests := [...][3]bool{ // a, b, want
+		{false, false, true},
+		{true, false, false},
+		{false, true, false},
+		{true, true, false},
+	}
+	for _, test := range tests {
+		a, b := test[0], test[1]
+		got := nor_ssa(a, b)
+		want := test[2]
+		if want != got {
+			print("nor(", a, ", ", b, ")=", want, " got ", got, "\n")
+			failed = true
+		}
+	}
+}
+
+var failed = false
+
+func main() {
+	testPhiControl()
+	if failed {
+		panic("failed")
+	}
+}

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -241,7 +241,7 @@
 (If (SETBE cmp) yes no) -> (ULE cmp yes no)
 (If (SETA cmp) yes no) -> (UGT cmp yes no)
 (If (SETAE cmp) yes no) -> (UGE cmp yes no)
-(If cond yes no) && cond.Op == OpAMD64MOVBload -> (NE (TESTB <TypeFlags> cond cond) yes no)
+(If cond yes no) -> (NE (TESTB <TypeFlags> cond cond) yes no)
 
 (StaticCall [argwid] {target} mem) -> (CALLstatic [argwid] {target} mem)
 (ClosureCall [argwid] entry closure mem) -> (CALLclosure [argwid] entry closure mem)

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -8068,16 +8068,13 @@ func rewriteBlockAMD64(b *Block) bool {
 	end9bea9963c3c5dfb97249a5feb8287f94:
 		;
 		// match: (If cond yes no)
-		// cond: cond.Op == OpAMD64MOVBload
+		// cond:
 		// result: (NE (TESTB <TypeFlags> cond cond) yes no)
 		{
 			v := b.Control
 			cond := v
 			yes := b.Succs[0]
 			no := b.Succs[1]
-			if !(cond.Op == OpAMD64MOVBload) {
-				goto end7e22019fb0effc80f85c05ea30bdb5d9
-			}
 			b.Kind = BlockAMD64NE
 			v0 := b.NewValue0(v.Line, OpAMD64TESTB, TypeInvalid)
 			v0.Type = TypeFlags
@@ -8088,8 +8085,8 @@ func rewriteBlockAMD64(b *Block) bool {
 			b.Succs[1] = no
 			return true
 		}
-		goto end7e22019fb0effc80f85c05ea30bdb5d9
+		goto end012351592edfc708bd3181d7e53f3993
-	end7e22019fb0effc80f85c05ea30bdb5d9:
+	end012351592edfc708bd3181d7e53f3993:
 		;
 	case BlockAMD64LE:
 		// match: (LE (InvertFlags cmp) yes no)