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[release-branch.go1.17] cmd/compile: correct type of pointer difference on RISCV64

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Pointer comparison is lowered to the following on RISCV64

(EqPtr x y) => (SEQZ (SUB <x.Type> x y))

The difference of two pointers (the SUB) should not be pointer
type. Otherwise it can cause the GC to find a bad pointer.

Updates #51101.
Fixes #51199.

Change-Id: I7e73c2155c36ff403c032981a9aa9cccbfdf0f64
Reviewed-on: https://go-review.googlesource.com/c/go/+/385655
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 1ed30ca537)
Reviewed-on: https://go-review.googlesource.com/c/go/+/386474
This commit is contained in:
Cherry Mui 2022-02-14 12:43:27 -05:00 committed by Dmitri Shuralyov
parent 1ba25fa288
commit 7d8fa65789
3 changed files with 44 additions and 6 deletions
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4
src/cmd/compile/internal/ssa/gen/RISCV64.rules
View File

@ -250,7 +250,7 @@
(Leq64F ...) => (FLED ...)
(Leq32F ...) => (FLES ...)
(EqPtr x y) => (SEQZ (SUB <x.Type> x y))
(EqPtr x y) => (SEQZ (SUB <typ.Uintptr> x y))
(Eq64 x y) => (SEQZ (SUB <x.Type> x y))
(Eq32 x y) => (SEQZ (SUB <x.Type> (ZeroExt32to64 x) (ZeroExt32to64 y)))
(Eq16 x y) => (SEQZ (SUB <x.Type> (ZeroExt16to64 x) (ZeroExt16to64 y)))
@ -258,7 +258,7 @@
(Eq64F ...) => (FEQD ...)
(Eq32F ...) => (FEQS ...)
(NeqPtr x y) => (SNEZ (SUB <x.Type> x y))
(NeqPtr x y) => (SNEZ (SUB <typ.Uintptr> x y))
(Neq64 x y) => (SNEZ (SUB <x.Type> x y))
(Neq32 x y) => (SNEZ (SUB <x.Type> (ZeroExt32to64 x) (ZeroExt32to64 y)))
(Neq16 x y) => (SNEZ (SUB <x.Type> (ZeroExt16to64 x) (ZeroExt16to64 y)))

10
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -1080,13 +1080,14 @@ func rewriteValueRISCV64_OpEqPtr(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
// match: (EqPtr x y)
// result: (SEQZ (SUB <x.Type> x y))
// result: (SEQZ (SUB <typ.Uintptr> x y))
for {
x := v_0
y := v_1
v.reset(OpRISCV64SEQZ)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, x.Type)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, typ.Uintptr)
v0.AddArg2(x, y)
v.AddArg(v0)
return true
@ -2629,13 +2630,14 @@ func rewriteValueRISCV64_OpNeqPtr(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
// match: (NeqPtr x y)
// result: (SNEZ (SUB <x.Type> x y))
// result: (SNEZ (SUB <typ.Uintptr> x y))
for {
x := v_0
y := v_1
v.reset(OpRISCV64SNEZ)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, x.Type)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, typ.Uintptr)
v0.AddArg2(x, y)
v.AddArg(v0)
return true

36
test/fixedbugs/issue51101.go Normal file
View File

@ -0,0 +1,36 @@
// run
// Copyright 2022 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 51101: on RISCV64, difference of two pointers
// was marked as pointer and crashes GC.
package main
var a, b int
func main() {
F(&b, &a)
}
//go:noinline
func F(a, b *int) bool {
x := a == b
G(x)
y := a != b
return y
}
//go:noinline
func G(bool) {
grow([1000]int{20})
}
func grow(x [1000]int) {
if x[0] != 0 {
x[0]--
grow(x)
}
}