diff --git a/src/cmd/compile/internal/ssa/deadstore.go b/src/cmd/compile/internal/ssa/deadstore.go index 1caa61a966..69616b3a88 100644 --- a/src/cmd/compile/internal/ssa/deadstore.go +++ b/src/cmd/compile/internal/ssa/deadstore.go @@ -197,7 +197,8 @@ func elimDeadAutosGeneric(f *Func) { panic("unhandled op with sym effect") } - if v.Uses == 0 || len(args) == 0 { + if v.Uses == 0 && v.Op != OpNilCheck || len(args) == 0 { + // Nil check has no use, but we need to keep it. return } diff --git a/test/fixedbugs/issue27278.go b/test/fixedbugs/issue27278.go new file mode 100644 index 0000000000..73f7c755e1 --- /dev/null +++ b/test/fixedbugs/issue27278.go @@ -0,0 +1,63 @@ +// run + +// Copyright 2018 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 27278: dead auto elim deletes an auto and its +// initialization, but it is live because of a nil check. + +package main + +type T struct { + _ [3]string + T2 +} + +func (t *T) M() []string { + return t.T2.M() +} + +type T2 struct { + T3 +} + +func (t *T2) M() []string { + return t.T3.M() +} + +type T3 struct { + a string +} + +func (t *T3) M() []string { + return []string{} +} + +func main() { + poison() + f() +} + +//go:noinline +func f() { + (&T{}).M() + grow(10000) +} + +// grow stack, triggers stack copy +func grow(n int) { + if n == 0 { + return + } + grow(n-1) +} + +// put some junk on stack, which cannot be valid address +//go:noinline +func poison() { + x := [10]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10} + g = x +} + +var g [10]int