[dev.ssa] cmd/compile: treat control ops as live at end of block

Failure to treat control ops as live can lead
to them being eliminated when they live in
other blocks.

Change-Id: I604a1977a3d3884b1f4516bea4e15885ce38272d
Reviewed-on: https://go-review.googlesource.com/13138
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssa/check.go b/src/cmd/compile/internal/ssa/check.go
index 4fe59e08d1bb29afcf1a302e433146c77d3f135a..1f6ffc0129ae2dbd6ee9d65939ef68c0eb4767f6 100644 (file)
--- a/src/cmd/compile/internal/ssa/check.go
+++ b/src/cmd/compile/internal/ssa/check.go
@@ -137,6 +137,13 @@ func checkFunc(f *Func) {
                }
        }
 
+       for _, b := range f.Blocks {
+               if b.Control != nil {
+                       if !valueMark[b.Control.ID] {
+                               f.Fatalf("control value for %s is missing: %v", b, b.Control)
+                       }
+               }
+       }
        for _, id := range f.bid.free {
                if blockMark[id] {
                        f.Fatalf("used block b%d in free list", id)

diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go
index 46efa9859e85dc921de23ddd6545a960b1a6f290..dac107dd18459336e96d873e667418e556fcc6f7 100644 (file)
--- a/src/cmd/compile/internal/ssa/regalloc.go
+++ b/src/cmd/compile/internal/ssa/regalloc.go
@@ -440,6 +440,9 @@ func live(f *Func) [][]ID {
                        // Start with known live values at the end of the block
                        s.clear()
                        s.addAll(live[b.ID])
+                       if b.Control != nil {
+                               s.add(b.Control.ID)
+                       }
 
                        // Propagate backwards to the start of the block
                        // Assumes Values have been scheduled.
@@ -456,7 +459,7 @@ func live(f *Func) [][]ID {
                        }
 
                        // for each predecessor of b, expand its list of live-at-end values
-                       // inv: s contains the values live at the start of b (excluding phi inputs)
+                       // invariant: s contains the values live at the start of b (excluding phi inputs)
                        for i, p := range b.Preds {
                                t.clear()
                                t.addAll(live[p.ID])

diff --git a/src/cmd/compile/internal/ssa/regalloc_test.go b/src/cmd/compile/internal/ssa/regalloc_test.go
new file mode 100644 (file)
index 0000000..dcd253e
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/regalloc_test.go
@@ -0,0 +1,32 @@
+// 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.
+
+package ssa
+
+import "testing"
+
+func TestLiveControlOps(t *testing.T) {
+       c := testConfig(t)
+       f := Fun(c, "entry",
+               Bloc("entry",
+                       Valu("mem", OpArg, TypeMem, 0, ".mem"),
+                       Valu("x", OpAMD64MOVBconst, TypeInt8, 0, 1),
+                       Valu("y", OpAMD64MOVBconst, TypeInt8, 0, 2),
+                       Valu("a", OpAMD64TESTB, TypeBool, 0, nil, "x", "y"),
+                       Valu("b", OpAMD64TESTB, TypeBool, 0, nil, "y", "x"),
+                       If("a", "if", "exit"),
+               ),
+               Bloc("if",
+                       If("b", "plain", "exit"),
+               ),
+               Bloc("plain",
+                       Goto("exit"),
+               ),
+               Bloc("exit",
+                       Exit("mem"),
+               ),
+       )
+       regalloc(f.f)
+       checkFunc(f.f)
+}