cmd/compile: fix loong64 constant folding in division rules

The divisor must be non-zero for the rule to be triggered.

Fixes #53018

Change-Id: Id56b8d986945bbb66e13131d11264ee438de5cb2
Reviewed-on: https://go-review.googlesource.com/c/go/+/407655
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: xiaodong liu <teaofmoli@gmail.com>
Reviewed-by: WANG Xuerui <git@xen0n.name>

src/cmd/compile/internal/ssa/gen/LOONG64.rules

@@ -617,10 +617,10 @@
 (SRLVconst [c] (MOVVconst [d]))  => (MOVVconst [int64(uint64(d)>>uint64(c))])
 (SRAVconst [c] (MOVVconst [d]))  => (MOVVconst [d>>uint64(c)])
 (Select1 (MULVU (MOVVconst [c]) (MOVVconst [d]))) => (MOVVconst [c*d])
-(Select1 (DIVV  (MOVVconst [c]) (MOVVconst [d]))) => (MOVVconst [c/d])
+(Select1 (DIVV  (MOVVconst [c]) (MOVVconst [d]))) && d != 0 => (MOVVconst [c/d])
-(Select1 (DIVVU (MOVVconst [c]) (MOVVconst [d]))) => (MOVVconst [int64(uint64(c)/uint64(d))])
+(Select1 (DIVVU (MOVVconst [c]) (MOVVconst [d]))) && d != 0 => (MOVVconst [int64(uint64(c)/uint64(d))])
-(Select0 (DIVV  (MOVVconst [c]) (MOVVconst [d]))) => (MOVVconst [c%d])   // mod
+(Select0 (DIVV  (MOVVconst [c]) (MOVVconst [d]))) && d != 0 => (MOVVconst [c%d])   // mod
-(Select0 (DIVVU (MOVVconst [c]) (MOVVconst [d]))) => (MOVVconst [int64(uint64(c)%uint64(d))]) // mod
+(Select0 (DIVVU (MOVVconst [c]) (MOVVconst [d]))) && d != 0 => (MOVVconst [int64(uint64(c)%uint64(d))]) // mod
 (ANDconst [c] (MOVVconst [d])) => (MOVVconst [c&d])
 (ANDconst [c] (ANDconst [d] x)) => (ANDconst [c&d] x)
 (ORconst [c] (MOVVconst [d])) => (MOVVconst [c|d])

src/cmd/compile/internal/ssa/rewriteLOONG64.go

@@ -6828,6 +6828,7 @@ func rewriteValueLOONG64_OpSelect0(v *Value) bool {
 		return true
 	}
 	// match: (Select0 (DIVV (MOVVconst [c]) (MOVVconst [d])))
+	// cond: d != 0
 	// result: (MOVVconst [c%d])
 	for {
 		if v_0.Op != OpLOONG64DIVV {
@@ -6844,11 +6845,15 @@ func rewriteValueLOONG64_OpSelect0(v *Value) bool {
 			break
 		}
 		d := auxIntToInt64(v_0_1.AuxInt)
+		if !(d != 0) {
+			break
+		}
 		v.reset(OpLOONG64MOVVconst)
 		v.AuxInt = int64ToAuxInt(c % d)
 		return true
 	}
 	// match: (Select0 (DIVVU (MOVVconst [c]) (MOVVconst [d])))
+	// cond: d != 0
 	// result: (MOVVconst [int64(uint64(c)%uint64(d))])
 	for {
 		if v_0.Op != OpLOONG64DIVVU {
@@ -6865,6 +6870,9 @@ func rewriteValueLOONG64_OpSelect0(v *Value) bool {
 			break
 		}
 		d := auxIntToInt64(v_0_1.AuxInt)
+		if !(d != 0) {
+			break
+		}
 		v.reset(OpLOONG64MOVVconst)
 		v.AuxInt = int64ToAuxInt(int64(uint64(c) % uint64(d)))
 		return true
@@ -7040,6 +7048,7 @@ func rewriteValueLOONG64_OpSelect1(v *Value) bool {
 		break
 	}
 	// match: (Select1 (DIVV (MOVVconst [c]) (MOVVconst [d])))
+	// cond: d != 0
 	// result: (MOVVconst [c/d])
 	for {
 		if v_0.Op != OpLOONG64DIVV {
@@ -7056,11 +7065,15 @@ func rewriteValueLOONG64_OpSelect1(v *Value) bool {
 			break
 		}
 		d := auxIntToInt64(v_0_1.AuxInt)
+		if !(d != 0) {
+			break
+		}
 		v.reset(OpLOONG64MOVVconst)
 		v.AuxInt = int64ToAuxInt(c / d)
 		return true
 	}
 	// match: (Select1 (DIVVU (MOVVconst [c]) (MOVVconst [d])))
+	// cond: d != 0
 	// result: (MOVVconst [int64(uint64(c)/uint64(d))])
 	for {
 		if v_0.Op != OpLOONG64DIVVU {
@@ -7077,6 +7090,9 @@ func rewriteValueLOONG64_OpSelect1(v *Value) bool {
 			break
 		}
 		d := auxIntToInt64(v_0_1.AuxInt)
+		if !(d != 0) {
+			break
+		}
 		v.reset(OpLOONG64MOVVconst)
 		v.AuxInt = int64ToAuxInt(int64(uint64(c) / uint64(d)))
 		return true

test/fixedbugs/issue53018.go

@@ -0,0 +1,30 @@
+// compile
+
+// 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 p
+
+var V []int
+
+func f(i int, c chan int) int {
+	arr := []int{0, 1}
+	for range c {
+		for a2 := range arr {
+			var a []int
+			V = V[:1/a2]
+			a[i] = 0
+		}
+		return func() int {
+			arr = []int{}
+			return func() int {
+				return func() int {
+					return func() int { return 4 }()
+				}()
+			}()
+		}()
+	}
+
+	return 0
+}