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cmd/compile: avoid using destination pointer base type in memmove optimization

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The type of the source and destination of a memmove call isn't
always accurate. It will always be a pointer (or an unsafe.Pointer), but
the base type might not be accurate. This comes about because multiple
copies of a pointer with different base types are coalesced into a single value.

In the failing example, the IData selector of the input argument is a
*[32]byte in one branch of the type switch, and a *[]byte in the other branch.
During the expand_calls pass both IDatas become just copies of the input
register. Those copies are deduped and an arbitrary one wins (in this case,
*[]byte is the unfortunate winner).

Generally an op v can rely on v.Type during rewrite rules. But relying
on v.Args[i].Type is discouraged.

Fixes #55122

Change-Id: I348fd9accf2058a87cd191eec01d39cda612f120
Reviewed-on: https://go-review.googlesource.com/c/go/+/431496
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
This commit is contained in:
Keith Randall 2022-09-17 18:52:35 -04:00 committed by Keith Randall
parent 0053ec452d
commit e283473ebb
4 changed files with 119 additions and 33 deletions
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17
src/cmd/compile/internal/ssa/gen/generic.rules
View File

@ -2112,7 +2112,13 @@
// Inline small or disjoint runtime.memmove calls with constant length.
// See the comment in op Move in genericOps.go for discussion of the type.
//
// Note that we've lost any knowledge of the type and alignment requirements
// of the source and destination. We only know the size, and that the type
// contains no pointers.
// The type of the move is not necessarily v.Args[0].Type().Elem()!
// See issue 55122 for details.
//
// Because expand calls runs after prove, constants useful to this pattern may not appear.
// Both versions need to exist; the memory and register variants.
//
@ -2120,31 +2126,28 @@
(SelectN [0] call:(StaticCall {sym} s1:(Store _ (Const(64|32) [sz]) s2:(Store _ src s3:(Store {t} _ dst mem)))))
&& sz >= 0
&& isSameCall(sym, "runtime.memmove")
&& t.IsPtr() // avoids TUNSAFEPTR, see issue 30061
&& s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1
&& isInlinableMemmove(dst, src, int64(sz), config)
&& clobber(s1, s2, s3, call)
=> (Move {t.Elem()} [int64(sz)] dst src mem)
=> (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
// Match post-expansion calls, register version.
(SelectN [0] call:(StaticCall {sym} dst src (Const(64|32) [sz]) mem))
&& sz >= 0
&& call.Uses == 1 // this will exclude all calls with results
&& isSameCall(sym, "runtime.memmove")
&& dst.Type.IsPtr() // avoids TUNSAFEPTR, see issue 30061
&& isInlinableMemmove(dst, src, int64(sz), config)
&& clobber(call)
=> (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
=> (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
// Match pre-expansion calls.
(SelectN [0] call:(StaticLECall {sym} dst src (Const(64|32) [sz]) mem))
&& sz >= 0
&& call.Uses == 1 // this will exclude all calls with results
&& isSameCall(sym, "runtime.memmove")
&& dst.Type.IsPtr() // avoids TUNSAFEPTR, see issue 30061
&& isInlinableMemmove(dst, src, int64(sz), config)
&& clobber(call)
=> (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
=> (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
// De-virtualize late-expanded interface calls into late-expanded static calls.
// Note that (ITab (IMake)) doesn't get rewritten until after the first opt pass,

50
src/cmd/compile/internal/ssa/rewritegeneric.go
View File

@ -26382,8 +26382,8 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
return true
}
// match: (SelectN [0] call:(StaticCall {sym} s1:(Store _ (Const64 [sz]) s2:(Store _ src s3:(Store {t} _ dst mem)))))
// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)
// result: (Move {t.Elem()} [int64(sz)] dst src mem)
// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)
// result: (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
for {
if auxIntToInt64(v.AuxInt) != 0 {
break
@ -26413,21 +26413,20 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
if s3.Op != OpStore {
break
}
t := auxToType(s3.Aux)
mem := s3.Args[2]
dst := s3.Args[1]
if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)) {
if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)) {
break
}
v.reset(OpMove)
v.AuxInt = int64ToAuxInt(int64(sz))
v.Aux = typeToAux(t.Elem())
v.Aux = typeToAux(types.Types[types.TUINT8])
v.AddArg3(dst, src, mem)
return true
}
// match: (SelectN [0] call:(StaticCall {sym} s1:(Store _ (Const32 [sz]) s2:(Store _ src s3:(Store {t} _ dst mem)))))
// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)
// result: (Move {t.Elem()} [int64(sz)] dst src mem)
// cond: sz >= 0 && isSameCall(sym, "runtime.memmove") && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)
// result: (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
for {
if auxIntToInt64(v.AuxInt) != 0 {
break
@ -26457,21 +26456,20 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
if s3.Op != OpStore {
break
}
t := auxToType(s3.Aux)
mem := s3.Args[2]
dst := s3.Args[1]
if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && t.IsPtr() && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)) {
if !(sz >= 0 && isSameCall(sym, "runtime.memmove") && s1.Uses == 1 && s2.Uses == 1 && s3.Uses == 1 && isInlinableMemmove(dst, src, int64(sz), config) && clobber(s1, s2, s3, call)) {
break
}
v.reset(OpMove)
v.AuxInt = int64ToAuxInt(int64(sz))
v.Aux = typeToAux(t.Elem())
v.Aux = typeToAux(types.Types[types.TUINT8])
v.AddArg3(dst, src, mem)
return true
}
// match: (SelectN [0] call:(StaticCall {sym} dst src (Const64 [sz]) mem))
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
for {
if auxIntToInt64(v.AuxInt) != 0 {
break
@ -26489,18 +26487,18 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
break
}
sz := auxIntToInt64(call_2.AuxInt)
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
break
}
v.reset(OpMove)
v.AuxInt = int64ToAuxInt(int64(sz))
v.Aux = typeToAux(dst.Type.Elem())
v.Aux = typeToAux(types.Types[types.TUINT8])
v.AddArg3(dst, src, mem)
return true
}
// match: (SelectN [0] call:(StaticCall {sym} dst src (Const32 [sz]) mem))
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
for {
if auxIntToInt64(v.AuxInt) != 0 {
break
@ -26518,18 +26516,18 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
break
}
sz := auxIntToInt32(call_2.AuxInt)
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
break
}
v.reset(OpMove)
v.AuxInt = int64ToAuxInt(int64(sz))
v.Aux = typeToAux(dst.Type.Elem())
v.Aux = typeToAux(types.Types[types.TUINT8])
v.AddArg3(dst, src, mem)
return true
}
// match: (SelectN [0] call:(StaticLECall {sym} dst src (Const64 [sz]) mem))
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
for {
if auxIntToInt64(v.AuxInt) != 0 {
break
@ -26547,18 +26545,18 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
break
}
sz := auxIntToInt64(call_2.AuxInt)
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
break
}
v.reset(OpMove)
v.AuxInt = int64ToAuxInt(int64(sz))
v.Aux = typeToAux(dst.Type.Elem())
v.Aux = typeToAux(types.Types[types.TUINT8])
v.AddArg3(dst, src, mem)
return true
}
// match: (SelectN [0] call:(StaticLECall {sym} dst src (Const32 [sz]) mem))
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {dst.Type.Elem()} [int64(sz)] dst src mem)
// cond: sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)
// result: (Move {types.Types[types.TUINT8]} [int64(sz)] dst src mem)
for {
if auxIntToInt64(v.AuxInt) != 0 {
break
@ -26576,12 +26574,12 @@ func rewriteValuegeneric_OpSelectN(v *Value) bool {
break
}
sz := auxIntToInt32(call_2.AuxInt)
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && dst.Type.IsPtr() && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
if !(sz >= 0 && call.Uses == 1 && isSameCall(sym, "runtime.memmove") && isInlinableMemmove(dst, src, int64(sz), config) && clobber(call)) {
break
}
v.reset(OpMove)
v.AuxInt = int64ToAuxInt(int64(sz))
v.Aux = typeToAux(dst.Type.Elem())
v.Aux = typeToAux(types.Types[types.TUINT8])
v.AddArg3(dst, src, mem)
return true
}

42
test/fixedbugs/issue55122.go Normal file
View File

@ -0,0 +1,42 @@
// 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.
package main
func main() {
for i := 0; i < 10000; i++ {
h(i)
sink = make([]byte, 1024) // generate some garbage
}
}
func h(iter int) {
var x [32]byte
for i := 0; i < 32; i++ {
x[i] = 99
}
g(&x)
if x == ([32]byte{}) {
return
}
for i := 0; i < 32; i++ {
println(x[i])
}
panic(iter)
}
//go:noinline
func g(x interface{}) {
switch e := x.(type) {
case *[32]byte:
var c [32]byte
*e = c
case *[]byte:
*e = nil
}
}
var sink []byte

43
test/fixedbugs/issue55122b.go Normal file
View File

@ -0,0 +1,43 @@
// 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.
package main
func main() {
for i := 0; i < 10000; i++ {
h(i)
sink = make([]byte, 1024) // generate some garbage
}
}
func h(iter int) {
var x [32]byte
for i := 0; i < 32; i++ {
x[i] = 99
}
g(&x)
if x == ([32]byte{}) {
return
}
for i := 0; i < 32; i++ {
println(x[i])
}
panic(iter)
}
//go:noinline
func g(x interface{}) {
switch e := x.(type) {
case *[32]byte:
var c [32]byte
*e = c
case *[3]*byte:
var c [3]*byte
*e = c
}
}
var sink []byte