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cmd/compile: optimize unsigned comparisons to 0

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There are some architecture-independent rules in #21439, since an
unsigned integer >= 0 is always true and < 0 is always false. This CL
adds these optimizations to generic rules.

Updates #21439

Change-Id: Iec7e3040b761ecb1e60908f764815fdd9bc62495
Reviewed-on: https://go-review.googlesource.com/c/go/+/246617
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Junchen Li 2020-07-10 11:39:23 +08:00 committed by Keith Randall
parent 1a35583418
commit e30fbe3757
3 changed files with 101 additions and 0 deletions
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4
src/cmd/compile/internal/ssa/gen/generic.rules
View File

@ -545,6 +545,10 @@
(Or(64|32|16|8) x (Or(64|32|16|8) x y)) => (Or(64|32|16|8) x y)
(Xor(64|32|16|8) x (Xor(64|32|16|8) x y)) => y
// Unsigned comparisons to zero.
(Less(64U|32U|16U|8U) _ (Const(64|32|16|8) [0])) => (ConstBool [false])
(Leq(64U|32U|16U|8U) (Const(64|32|16|8) [0]) _) => (ConstBool [true])
// Ands clear bits. Ors set bits.
// If a subsequent Or will set all the bits
// that an And cleared, we can skip the And.

80
src/cmd/compile/internal/ssa/rewritegeneric.go
View File

@ -9701,6 +9701,16 @@ func rewriteValuegeneric_OpLeq16U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint16(c) <= uint16(d))
return true
}
// match: (Leq16U (Const16 [0]) _)
// result: (ConstBool [true])
for {
if v_0.Op != OpConst16 || auxIntToInt16(v_0.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(true)
return true
}
return false
}
func rewriteValuegeneric_OpLeq32(v *Value) bool {
@ -9805,6 +9815,16 @@ func rewriteValuegeneric_OpLeq32U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint32(c) <= uint32(d))
return true
}
// match: (Leq32U (Const32 [0]) _)
// result: (ConstBool [true])
for {
if v_0.Op != OpConst32 || auxIntToInt32(v_0.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(true)
return true
}
return false
}
func rewriteValuegeneric_OpLeq64(v *Value) bool {
@ -9909,6 +9929,16 @@ func rewriteValuegeneric_OpLeq64U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint64(c) <= uint64(d))
return true
}
// match: (Leq64U (Const64 [0]) _)
// result: (ConstBool [true])
for {
if v_0.Op != OpConst64 || auxIntToInt64(v_0.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(true)
return true
}
return false
}
func rewriteValuegeneric_OpLeq8(v *Value) bool {
@ -9993,6 +10023,16 @@ func rewriteValuegeneric_OpLeq8U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint8(c) <= uint8(d))
return true
}
// match: (Leq8U (Const8 [0]) _)
// result: (ConstBool [true])
for {
if v_0.Op != OpConst8 || auxIntToInt8(v_0.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(true)
return true
}
return false
}
func rewriteValuegeneric_OpLess16(v *Value) bool {
@ -10033,6 +10073,16 @@ func rewriteValuegeneric_OpLess16U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint16(c) < uint16(d))
return true
}
// match: (Less16U _ (Const16 [0]))
// result: (ConstBool [false])
for {
if v_1.Op != OpConst16 || auxIntToInt16(v_1.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(false)
return true
}
return false
}
func rewriteValuegeneric_OpLess32(v *Value) bool {
@ -10093,6 +10143,16 @@ func rewriteValuegeneric_OpLess32U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint32(c) < uint32(d))
return true
}
// match: (Less32U _ (Const32 [0]))
// result: (ConstBool [false])
for {
if v_1.Op != OpConst32 || auxIntToInt32(v_1.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(false)
return true
}
return false
}
func rewriteValuegeneric_OpLess64(v *Value) bool {
@ -10153,6 +10213,16 @@ func rewriteValuegeneric_OpLess64U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint64(c) < uint64(d))
return true
}
// match: (Less64U _ (Const64 [0]))
// result: (ConstBool [false])
for {
if v_1.Op != OpConst64 || auxIntToInt64(v_1.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(false)
return true
}
return false
}
func rewriteValuegeneric_OpLess8(v *Value) bool {
@ -10193,6 +10263,16 @@ func rewriteValuegeneric_OpLess8U(v *Value) bool {
v.AuxInt = boolToAuxInt(uint8(c) < uint8(d))
return true
}
// match: (Less8U _ (Const8 [0]))
// result: (ConstBool [false])
for {
if v_1.Op != OpConst8 || auxIntToInt8(v_1.AuxInt) != 0 {
break
}
v.reset(OpConstBool)
v.AuxInt = boolToAuxInt(false)
return true
}
return false
}
func rewriteValuegeneric_OpLoad(v *Value) bool {

17
test/codegen/comparisons.go
View File

@ -407,3 +407,20 @@ func CmpToZero_ex5(e, f int32, u uint32) int {
}
return 0
}
func UintLtZero(a uint8, b uint16, c uint32, d uint64) int {
// amd64: -`(TESTB|TESTW|TESTL|TESTQ|JCC|JCS)`
// arm64: -`(CMPW|CMP|BHS|BLO)`
if a < 0 || b < 0 || c < 0 || d < 0 {
return 1
}
return 0
}
func UintGeqZero(a uint8, b uint16, c uint32, d uint64) int {
// amd64: -`(TESTB|TESTW|TESTL|TESTQ|JCS|JCC)`
// arm64: -`(CMPW|CMP|BLO|BHS)`
if a >= 0 || b >= 0 || c >= 0 || d >= 0 {
return 1
}
return 0
}