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

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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>
This commit is contained in:
Josh Bleecher Snyder 2015-08-04 14:22:29 -07:00
parent 54dca047dd
commit 573c791e81
3 changed files with 43 additions and 1 deletions
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7
src/cmd/compile/internal/ssa/check.go
View File

@ -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)

5
src/cmd/compile/internal/ssa/regalloc.go
View File

@ -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])

32
src/cmd/compile/internal/ssa/regalloc_test.go Normal file
View File

@ -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)
}