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cmd/compile: don't fuse branches with side effects

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Count Values with side effects but no use as live, and don't fuse
branches that contain such Values. (This can happen e.g. when it
is followed by an infinite loop.) Otherwise this may lead to
miscompilation (side effect fired at wrong condition) or ICE (two
stores live simultaneously).

Fixes #36005.

Change-Id: If202eae4b37cb7f0311d6ca120ffa46609925157
Reviewed-on: https://go-review.googlesource.com/c/go/+/210179
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Cherry Zhang 2019-12-05 18:56:54 -05:00
parent eeb319a5a5
commit 7673884a7f
4 changed files with 39 additions and 3 deletions
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38
src/cmd/compile/internal/ssa/fuse_test.go
View file

@ -63,7 +63,7 @@ func TestFuseEliminatesBothBranches(t *testing.T) {
t.Errorf("then was not eliminated, but should have")
}
if b == fun.blocks["else"] && b.Kind != BlockInvalid {
t.Errorf("then was not eliminated, but should have")
t.Errorf("else was not eliminated, but should have")
}
}
}
@ -97,7 +97,7 @@ func TestFuseHandlesPhis(t *testing.T) {
t.Errorf("then was not eliminated, but should have")
}
if b == fun.blocks["else"] && b.Kind != BlockInvalid {
t.Errorf("then was not eliminated, but should have")
t.Errorf("else was not eliminated, but should have")
}
}
}
@ -131,6 +131,40 @@ func TestFuseEliminatesEmptyBlocks(t *testing.T) {
}
}
func TestFuseSideEffects(t *testing.T) {
// Test that we don't fuse branches that have side effects but
// have no use (e.g. followed by infinite loop).
// See issue #36005.
c := testConfig(t)
fun := c.Fun("entry",
Bloc("entry",
Valu("mem", OpInitMem, types.TypeMem, 0, nil),
Valu("b", OpArg, c.config.Types.Bool, 0, nil),
If("b", "then", "else")),
Bloc("then",
Valu("call1", OpStaticCall, types.TypeMem, 0, nil, "mem"),
Goto("empty")),
Bloc("else",
Valu("call2", OpStaticCall, types.TypeMem, 0, nil, "mem"),
Goto("empty")),
Bloc("empty",
Goto("loop")),
Bloc("loop",
Goto("loop")))
CheckFunc(fun.f)
fuseAll(fun.f)
for _, b := range fun.f.Blocks {
if b == fun.blocks["then"] && b.Kind == BlockInvalid {
t.Errorf("then is eliminated, but should not")
}
if b == fun.blocks["else"] && b.Kind == BlockInvalid {
t.Errorf("else is eliminated, but should not")
}
}
}
func BenchmarkFuse(b *testing.B) {
for _, n := range [...]int{1, 10, 100, 1000, 10000} {
b.Run(strconv.Itoa(n), func(b *testing.B) {