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

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 1ed30ca537a05b887f8479027b6363a03f957610)
Reviewed-on: https://go-review.googlesource.com/c/go/+/386474

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index 9cdd62edbe01c004f4b79951d38a4d5cd123a2a3..1afd39488cd7b646faf639bce627ab2205504fa1 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -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)))

diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index 431fb1aaf66e0dd288704707d9ed909780533d4b..c1299bf1e207dfcc9b9a1c1609ebf6c1ac27e409 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -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

diff --git a/test/fixedbugs/issue51101.go b/test/fixedbugs/issue51101.go
new file mode 100644 (file)
index 0000000..a390e50
--- /dev/null
+++ b/test/fixedbugs/issue51101.go
@@ -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)
+       }
+}