cmd/compile: fix If lowering on ARM64

On ARM64, an If block is lowered to (NZ cond yes no). This is
incorrect because cond is a boolean value and therefore only the
last byte is meaningful (same as AMD64, see ARM64Ops.go). But here
we are comparing a full register width with 0. Correct it by
comparing only the last bit.

Fixes #52788.

Change-Id: I2cacf9f3d2f45e149c361a290f511b2d4ed845c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/405114
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>

src/cmd/compile/internal/ssa/gen/ARM64.rules

@@ -532,7 +532,7 @@
 (If (GreaterThanF cc) yes no) => (FGT cc yes no)
 (If (GreaterEqualF cc) yes no) => (FGE cc yes no)
 
-(If cond yes no) => (NZ cond yes no)
+(If cond yes no) => (TBNZ [0] cond yes no)
 
 // atomic intrinsics
 // Note: these ops do not accept offset.
@@ -593,6 +593,21 @@
 (NZ (GreaterThanF cc) yes no) => (FGT cc yes no)
 (NZ (GreaterEqualF cc) yes no) => (FGE cc yes no)
 
+(TBNZ [0] (Equal cc) yes no) => (EQ cc yes no)
+(TBNZ [0] (NotEqual cc) yes no) => (NE cc yes no)
+(TBNZ [0] (LessThan cc) yes no) => (LT cc yes no)
+(TBNZ [0] (LessThanU cc) yes no) => (ULT cc yes no)
+(TBNZ [0] (LessEqual cc) yes no) => (LE cc yes no)
+(TBNZ [0] (LessEqualU cc) yes no) => (ULE cc yes no)
+(TBNZ [0] (GreaterThan cc) yes no) => (GT cc yes no)
+(TBNZ [0] (GreaterThanU cc) yes no) => (UGT cc yes no)
+(TBNZ [0] (GreaterEqual cc) yes no) => (GE cc yes no)
+(TBNZ [0] (GreaterEqualU cc) yes no) => (UGE cc yes no)
+(TBNZ [0] (LessThanF cc) yes no) => (FLT cc yes no)
+(TBNZ [0] (LessEqualF cc) yes no) => (FLE cc yes no)
+(TBNZ [0] (GreaterThanF cc) yes no) => (FGT cc yes no)
+(TBNZ [0] (GreaterEqualF cc) yes no) => (FGE cc yes no)
+
 (EQ (CMPWconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 => (EQ (TSTWconst [int32(c)] y) yes no)
 (NE (CMPWconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 => (NE (TSTWconst [int32(c)] y) yes no)
 (LT (CMPWconst [0] x:(ANDconst [c] y)) yes no) && x.Uses == 1 => (LT (TSTWconst [int32(c)] y) yes no)

src/cmd/compile/internal/ssa/rewriteARM64.go

@@ -28696,10 +28696,11 @@ func rewriteBlockARM64(b *Block) bool {
 			return true
 		}
 		// match: (If cond yes no)
-		// result: (NZ cond yes no)
+		// result: (TBNZ [0] cond yes no)
 		for {
 			cond := b.Controls[0]
-			b.resetWithControl(BlockARM64NZ, cond)
+			b.resetWithControl(BlockARM64TBNZ, cond)
+			b.AuxInt = int64ToAuxInt(0)
 			return true
 		}
 	case BlockARM64LE:
@@ -30088,6 +30089,161 @@ func rewriteBlockARM64(b *Block) bool {
 			b.Reset(BlockFirst)
 			return true
 		}
+	case BlockARM64TBNZ:
+		// match: (TBNZ [0] (Equal cc) yes no)
+		// result: (EQ cc yes no)
+		for b.Controls[0].Op == OpARM64Equal {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64EQ, cc)
+			return true
+		}
+		// match: (TBNZ [0] (NotEqual cc) yes no)
+		// result: (NE cc yes no)
+		for b.Controls[0].Op == OpARM64NotEqual {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64NE, cc)
+			return true
+		}
+		// match: (TBNZ [0] (LessThan cc) yes no)
+		// result: (LT cc yes no)
+		for b.Controls[0].Op == OpARM64LessThan {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64LT, cc)
+			return true
+		}
+		// match: (TBNZ [0] (LessThanU cc) yes no)
+		// result: (ULT cc yes no)
+		for b.Controls[0].Op == OpARM64LessThanU {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64ULT, cc)
+			return true
+		}
+		// match: (TBNZ [0] (LessEqual cc) yes no)
+		// result: (LE cc yes no)
+		for b.Controls[0].Op == OpARM64LessEqual {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64LE, cc)
+			return true
+		}
+		// match: (TBNZ [0] (LessEqualU cc) yes no)
+		// result: (ULE cc yes no)
+		for b.Controls[0].Op == OpARM64LessEqualU {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64ULE, cc)
+			return true
+		}
+		// match: (TBNZ [0] (GreaterThan cc) yes no)
+		// result: (GT cc yes no)
+		for b.Controls[0].Op == OpARM64GreaterThan {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64GT, cc)
+			return true
+		}
+		// match: (TBNZ [0] (GreaterThanU cc) yes no)
+		// result: (UGT cc yes no)
+		for b.Controls[0].Op == OpARM64GreaterThanU {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64UGT, cc)
+			return true
+		}
+		// match: (TBNZ [0] (GreaterEqual cc) yes no)
+		// result: (GE cc yes no)
+		for b.Controls[0].Op == OpARM64GreaterEqual {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64GE, cc)
+			return true
+		}
+		// match: (TBNZ [0] (GreaterEqualU cc) yes no)
+		// result: (UGE cc yes no)
+		for b.Controls[0].Op == OpARM64GreaterEqualU {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64UGE, cc)
+			return true
+		}
+		// match: (TBNZ [0] (LessThanF cc) yes no)
+		// result: (FLT cc yes no)
+		for b.Controls[0].Op == OpARM64LessThanF {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64FLT, cc)
+			return true
+		}
+		// match: (TBNZ [0] (LessEqualF cc) yes no)
+		// result: (FLE cc yes no)
+		for b.Controls[0].Op == OpARM64LessEqualF {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64FLE, cc)
+			return true
+		}
+		// match: (TBNZ [0] (GreaterThanF cc) yes no)
+		// result: (FGT cc yes no)
+		for b.Controls[0].Op == OpARM64GreaterThanF {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64FGT, cc)
+			return true
+		}
+		// match: (TBNZ [0] (GreaterEqualF cc) yes no)
+		// result: (FGE cc yes no)
+		for b.Controls[0].Op == OpARM64GreaterEqualF {
+			v_0 := b.Controls[0]
+			cc := v_0.Args[0]
+			if auxIntToInt64(b.AuxInt) != 0 {
+				break
+			}
+			b.resetWithControl(BlockARM64FGE, cc)
+			return true
+		}
 	case BlockARM64UGE:
 		// match: (UGE (FlagConstant [fc]) yes no)
 		// cond: fc.uge()

test/fixedbugs/issue52788.go

@@ -0,0 +1,27 @@
+// 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 52788: miscompilation for boolean comparison on ARM64.
+
+package main
+
+import (
+	"fmt"
+	"reflect"
+)
+
+func f(next func() bool) {
+	for b := next(); b; b = next() {
+		fmt.Printf("next() returned %v\n", b)
+	}
+}
+
+func main() {
+	next := reflect.MakeFunc(reflect.TypeOf((func() bool)(nil)), func(_ []reflect.Value) []reflect.Value {
+		return []reflect.Value{reflect.ValueOf(false)}
+	})
+	reflect.ValueOf(f).Call([]reflect.Value{next})
+}