cmd/compile: optimize unsigned comparisons to 0
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>
diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index ed5bfc8..2d39d27 100644
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -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.
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index 9f4e1b9..68e49f4 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -9701,6 +9701,16 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 {
diff --git a/test/codegen/comparisons.go b/test/codegen/comparisons.go
index 9080857..f3c1553 100644
--- a/test/codegen/comparisons.go
+++ b/test/codegen/comparisons.go
@@ -407,3 +407,20 @@
}
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
+}
