diff options
| -rw-r--r-- | src/cmd/compile/internal/gc/const.go | 11 | ||||
| -rw-r--r-- | src/cmd/compile/internal/gc/walk.go | 6 | ||||
| -rw-r--r-- | test/fixedbugs/issue27143.go | 17 |
3 files changed, 34 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/gc/const.go b/src/cmd/compile/internal/gc/const.go index dcc16b6dec..32af1fb3fa 100644 --- a/src/cmd/compile/internal/gc/const.go +++ b/src/cmd/compile/internal/gc/const.go @@ -122,6 +122,17 @@ func (n *Node) Int64() int64 { return n.Val().U.(*Mpint).Int64() } +// CanInt64 reports whether it is safe to call Int64() on n. +func (n *Node) CanInt64() bool { + if !Isconst(n, CTINT) { + return false + } + + // if the value inside n cannot be represented as an int64, the + // return value of Int64 is undefined + return n.Val().U.(*Mpint).CmpInt64(n.Int64()) == 0 +} + // Bool returns n as a bool. // n must be a boolean constant. func (n *Node) Bool() bool { diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go index ca3025bbaa..79134067c6 100644 --- a/src/cmd/compile/internal/gc/walk.go +++ b/src/cmd/compile/internal/gc/walk.go @@ -3561,6 +3561,12 @@ func walkinrange(n *Node, init *Nodes) *Node { return n } + // Ensure that Int64() does not overflow on a and c (it'll happen + // for any const above 2**63; see issue #27143). + if !a.CanInt64() || !c.CanInt64() { + return n + } + if opl == OLT { // We have a < b && ... // We need a ≤ b && ... to safely use unsigned comparison tricks. diff --git a/test/fixedbugs/issue27143.go b/test/fixedbugs/issue27143.go new file mode 100644 index 0000000000..009ec9f6c2 --- /dev/null +++ b/test/fixedbugs/issue27143.go @@ -0,0 +1,17 @@ +// compile + +// 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 27143: cmd/compile: erroneous application of walkinrange +// optimization for const over 2**63 + +package p + +var c uint64 + +var b1 bool = 0x7fffffffffffffff < c && c < 0x8000000000000000 +var b2 bool = c < 0x8000000000000000 && 0x7fffffffffffffff < c +var b3 bool = 0x8000000000000000 < c && c < 0x8000000000000001 +var b4 bool = c < 0x8000000000000001 && 0x8000000000000000 < c |