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cmd/compile: simplify less with non-negative number and constant 0 or 1

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The most common cases:
len(s) > 0
len(s) < 1

and they can be simplified to:
len(s) != 0
len(s) == 0

Fixes #48054

Change-Id: I16e5b0cffcfab62a4acc2a09977a6cd3543dd000
Reviewed-on: https://go-review.googlesource.com/c/go/+/346050
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
wdvxdr 2021-08-30 22:26:54 +08:00 committed by Cherry Mui
parent 6226020c2f
commit 21de6bc463
3 changed files with 194 additions and 0 deletions
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3
src/cmd/compile/internal/ssa/gen/generic.rules
View file

@ -500,6 +500,9 @@
(Leq32 (Const32 [0]) (Rsh32Ux64 _ (Const64 [c]))) && c > 0 => (ConstBool [true])
(Leq64 (Const64 [0]) (Rsh64Ux64 _ (Const64 [c]))) && c > 0 => (ConstBool [true])
(Less(64|32|16|8) (Const(64|32|16|8) <t> [0]) x) && isNonNegative(x) => (Neq(64|32|16|8) (Const(64|32|16|8) <t> [0]) x)
(Less(64|32|16|8) x (Const(64|32|16|8) <t> [1])) && isNonNegative(x) => (Eq(64|32|16|8) (Const(64|32|16|8) <t> [0]) x)
// constant floating point comparisons
(Eq32F (Const32F [c]) (Const32F [d])) => (ConstBool [c == d])
(Eq64F (Const64F [c]) (Const64F [d])) => (ConstBool [c == d])

160
src/cmd/compile/internal/ssa/rewritegeneric.go
View file

@ -10083,6 +10083,7 @@ func rewriteValuegeneric_OpLeq8U(v *Value) bool {
func rewriteValuegeneric_OpLess16(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
// match: (Less16 (Const16 [c]) (Const16 [d]))
// result: (ConstBool [c < d])
for {
@ -10098,6 +10099,45 @@ func rewriteValuegeneric_OpLess16(v *Value) bool {
v.AuxInt = boolToAuxInt(c < d)
return true
}
// match: (Less16 (Const16 <t> [0]) x)
// cond: isNonNegative(x)
// result: (Neq16 (Const16 <t> [0]) x)
for {
if v_0.Op != OpConst16 {
break
}
t := v_0.Type
if auxIntToInt16(v_0.AuxInt) != 0 {
break
}
x := v_1
if !(isNonNegative(x)) {
break
}
v.reset(OpNeq16)
v0 := b.NewValue0(v.Pos, OpConst16, t)
v0.AuxInt = int16ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
// match: (Less16 x (Const16 <t> [1]))
// cond: isNonNegative(x)
// result: (Eq16 (Const16 <t> [0]) x)
for {
x := v_0
if v_1.Op != OpConst16 {
break
}
t := v_1.Type
if auxIntToInt16(v_1.AuxInt) != 1 || !(isNonNegative(x)) {
break
}
v.reset(OpEq16)
v0 := b.NewValue0(v.Pos, OpConst16, t)
v0.AuxInt = int16ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
return false
}
func rewriteValuegeneric_OpLess16U(v *Value) bool {
@ -10133,6 +10173,7 @@ func rewriteValuegeneric_OpLess16U(v *Value) bool {
func rewriteValuegeneric_OpLess32(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
// match: (Less32 (Const32 [c]) (Const32 [d]))
// result: (ConstBool [c < d])
for {
@ -10148,6 +10189,45 @@ func rewriteValuegeneric_OpLess32(v *Value) bool {
v.AuxInt = boolToAuxInt(c < d)
return true
}
// match: (Less32 (Const32 <t> [0]) x)
// cond: isNonNegative(x)
// result: (Neq32 (Const32 <t> [0]) x)
for {
if v_0.Op != OpConst32 {
break
}
t := v_0.Type
if auxIntToInt32(v_0.AuxInt) != 0 {
break
}
x := v_1
if !(isNonNegative(x)) {
break
}
v.reset(OpNeq32)
v0 := b.NewValue0(v.Pos, OpConst32, t)
v0.AuxInt = int32ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
// match: (Less32 x (Const32 <t> [1]))
// cond: isNonNegative(x)
// result: (Eq32 (Const32 <t> [0]) x)
for {
x := v_0
if v_1.Op != OpConst32 {
break
}
t := v_1.Type
if auxIntToInt32(v_1.AuxInt) != 1 || !(isNonNegative(x)) {
break
}
v.reset(OpEq32)
v0 := b.NewValue0(v.Pos, OpConst32, t)
v0.AuxInt = int32ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
return false
}
func rewriteValuegeneric_OpLess32F(v *Value) bool {
@ -10203,6 +10283,7 @@ func rewriteValuegeneric_OpLess32U(v *Value) bool {
func rewriteValuegeneric_OpLess64(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
// match: (Less64 (Const64 [c]) (Const64 [d]))
// result: (ConstBool [c < d])
for {
@ -10218,6 +10299,45 @@ func rewriteValuegeneric_OpLess64(v *Value) bool {
v.AuxInt = boolToAuxInt(c < d)
return true
}
// match: (Less64 (Const64 <t> [0]) x)
// cond: isNonNegative(x)
// result: (Neq64 (Const64 <t> [0]) x)
for {
if v_0.Op != OpConst64 {
break
}
t := v_0.Type
if auxIntToInt64(v_0.AuxInt) != 0 {
break
}
x := v_1
if !(isNonNegative(x)) {
break
}
v.reset(OpNeq64)
v0 := b.NewValue0(v.Pos, OpConst64, t)
v0.AuxInt = int64ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
// match: (Less64 x (Const64 <t> [1]))
// cond: isNonNegative(x)
// result: (Eq64 (Const64 <t> [0]) x)
for {
x := v_0
if v_1.Op != OpConst64 {
break
}
t := v_1.Type
if auxIntToInt64(v_1.AuxInt) != 1 || !(isNonNegative(x)) {
break
}
v.reset(OpEq64)
v0 := b.NewValue0(v.Pos, OpConst64, t)
v0.AuxInt = int64ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
return false
}
func rewriteValuegeneric_OpLess64F(v *Value) bool {
@ -10273,6 +10393,7 @@ func rewriteValuegeneric_OpLess64U(v *Value) bool {
func rewriteValuegeneric_OpLess8(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
// match: (Less8 (Const8 [c]) (Const8 [d]))
// result: (ConstBool [c < d])
for {
@ -10288,6 +10409,45 @@ func rewriteValuegeneric_OpLess8(v *Value) bool {
v.AuxInt = boolToAuxInt(c < d)
return true
}
// match: (Less8 (Const8 <t> [0]) x)
// cond: isNonNegative(x)
// result: (Neq8 (Const8 <t> [0]) x)
for {
if v_0.Op != OpConst8 {
break
}
t := v_0.Type
if auxIntToInt8(v_0.AuxInt) != 0 {
break
}
x := v_1
if !(isNonNegative(x)) {
break
}
v.reset(OpNeq8)
v0 := b.NewValue0(v.Pos, OpConst8, t)
v0.AuxInt = int8ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
// match: (Less8 x (Const8 <t> [1]))
// cond: isNonNegative(x)
// result: (Eq8 (Const8 <t> [0]) x)
for {
x := v_0
if v_1.Op != OpConst8 {
break
}
t := v_1.Type
if auxIntToInt8(v_1.AuxInt) != 1 || !(isNonNegative(x)) {
break
}
v.reset(OpEq8)
v0 := b.NewValue0(v.Pos, OpConst8, t)
v0.AuxInt = int8ToAuxInt(0)
v.AddArg2(v0, x)
return true
}
return false
}
func rewriteValuegeneric_OpLess8U(v *Value) bool {

31
test/codegen/issue48054.go Normal file
View file

@ -0,0 +1,31 @@
// asmcheck
// Copyright 2021 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 a(n string) bool {
// arm64:"CBZ"
if len(n) > 0 {
return true
}
return false
}
func a2(n []int) bool {
// arm64:"CBZ"
if len(n) > 0 {
return true
}
return false
}
func a3(n []int) bool {
// amd64:"TESTQ"
if len(n) < 1 {
return true
}
return false
}