cmd/compile: fix slice-in-bound check on amd64p32

Should use CMPL instead of CMPQ.

Fixes #20811.

Change-Id: I610d487949c2c8a08b3743656149069d931a51bb
Reviewed-on: https://go-review.googlesource.com/46870Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -441,8 +441,10 @@
 (Convert <t> x mem) && config.PtrSize == 4 -> (MOVLconvert <t> x mem)
 (IsNonNil p) && config.PtrSize == 8 -> (SETNE (TESTQ p p))
 (IsNonNil p) && config.PtrSize == 4 -> (SETNE (TESTL p p))
-(IsInBounds idx len) -> (SETB (CMPQ idx len))
-(IsSliceInBounds idx len) -> (SETBE (CMPQ idx len))
+(IsInBounds idx len) && config.PtrSize == 8 -> (SETB (CMPQ idx len))
+(IsInBounds idx len) && config.PtrSize == 4 -> (SETB (CMPL idx len))
+(IsSliceInBounds idx len) && config.PtrSize == 8 -> (SETBE (CMPQ idx len))
+(IsSliceInBounds idx len) && config.PtrSize == 4 -> (SETBE (CMPL idx len))
 (NilCheck ptr mem) -> (LoweredNilCheck ptr mem)
 (GetG mem) -> (LoweredGetG mem)
 (GetClosurePtr) -> (LoweredGetClosurePtr)

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -39253,13 +39253,18 @@ func rewriteValueAMD64_OpInterCall_0(v *Value) bool {
 func rewriteValueAMD64_OpIsInBounds_0(v *Value) bool {
 	b := v.Block
 	_ = b
+	config := b.Func.Config
+	_ = config
 	// match: (IsInBounds idx len)
-	// cond:
+	// cond: config.PtrSize == 8
 	// result: (SETB (CMPQ idx len))
 	for {
 		_ = v.Args[1]
 		idx := v.Args[0]
 		len := v.Args[1]
+		if !(config.PtrSize == 8) {
+			break
+		}
 		v.reset(OpAMD64SETB)
 		v0 := b.NewValue0(v.Pos, OpAMD64CMPQ, types.TypeFlags)
 		v0.AddArg(idx)
@@ -39267,6 +39272,24 @@ func rewriteValueAMD64_OpIsInBounds_0(v *Value) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (IsInBounds idx len)
+	// cond: config.PtrSize == 4
+	// result: (SETB (CMPL idx len))
+	for {
+		_ = v.Args[1]
+		idx := v.Args[0]
+		len := v.Args[1]
+		if !(config.PtrSize == 4) {
+			break
+		}
+		v.reset(OpAMD64SETB)
+		v0 := b.NewValue0(v.Pos, OpAMD64CMPL, types.TypeFlags)
+		v0.AddArg(idx)
+		v0.AddArg(len)
+		v.AddArg(v0)
+		return true
+	}
+	return false
 }
 func rewriteValueAMD64_OpIsNonNil_0(v *Value) bool {
 	b := v.Block
@@ -39308,13 +39331,18 @@ func rewriteValueAMD64_OpIsNonNil_0(v *Value) bool {
 func rewriteValueAMD64_OpIsSliceInBounds_0(v *Value) bool {
 	b := v.Block
 	_ = b
+	config := b.Func.Config
+	_ = config
 	// match: (IsSliceInBounds idx len)
-	// cond:
+	// cond: config.PtrSize == 8
 	// result: (SETBE (CMPQ idx len))
 	for {
 		_ = v.Args[1]
 		idx := v.Args[0]
 		len := v.Args[1]
+		if !(config.PtrSize == 8) {
+			break
+		}
 		v.reset(OpAMD64SETBE)
 		v0 := b.NewValue0(v.Pos, OpAMD64CMPQ, types.TypeFlags)
 		v0.AddArg(idx)
@@ -39322,6 +39350,24 @@ func rewriteValueAMD64_OpIsSliceInBounds_0(v *Value) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (IsSliceInBounds idx len)
+	// cond: config.PtrSize == 4
+	// result: (SETBE (CMPL idx len))
+	for {
+		_ = v.Args[1]
+		idx := v.Args[0]
+		len := v.Args[1]
+		if !(config.PtrSize == 4) {
+			break
+		}
+		v.reset(OpAMD64SETBE)
+		v0 := b.NewValue0(v.Pos, OpAMD64CMPL, types.TypeFlags)
+		v0.AddArg(idx)
+		v0.AddArg(len)
+		v.AddArg(v0)
+		return true
+	}
+	return false
 }
 func rewriteValueAMD64_OpLeq16_0(v *Value) bool {
 	b := v.Block

test/fixedbugs/issue20811.go

+// run
+
+// Copyright 2017 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 20811: slice-in-bound check is lowered incorrectly on
+// amd64p32.
+
+package main
+
+func main() {
+	i := g()
+	_ = "x"[int32(i)]
+	j := g()
+	_ = "x"[:int32(j)]
+}
+
+//go:noinline
+func g() int64 {
+	return 4398046511104
+}
+