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cmd/compile: optimize absorbing InvertFlags into Noov comparisons for arm64

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Previously (LessThanNoov (InvertFlags x)) is lowered as:
CSET
CSET
BIC
With this CL it's lowered as:
CSET
CSEL
This saves one instruction.

Similarly (GreaterEqualNoov (InvertFlags x)) is now lowered as:
CSET
CSINC

$ benchstat old.bench new.bench
goos: linux
goarch: arm64
                       │  old.bench  │             new.bench              │
                       │   sec/op    │   sec/op     vs base               │
InvertLessThanNoov-160   2.249n ± 2%   2.190n ± 1%  -2.62% (p=0.003 n=10)

Change-Id: Idd8979b7f4fe466e74b1a201c4aba7f1b0cffb0b
Reviewed-on: https://go-review.googlesource.com/c/go/+/526237
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Eric Fang <eric.fang@arm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
eric fang 2023-09-12 03:01:33 +00:00 committed by Eric Fang
parent dd881027c3
commit ace1494d92
4 changed files with 43 additions and 12 deletions
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4
src/cmd/compile/internal/ssa/_gen/ARM64.rules
View file

@ -1569,8 +1569,8 @@
(LessEqualF (InvertFlags x)) => (GreaterEqualF x)
(GreaterThanF (InvertFlags x)) => (LessThanF x)
(GreaterEqualF (InvertFlags x)) => (LessEqualF x)
(LessThanNoov (InvertFlags x)) => (BIC (GreaterEqualNoov <typ.Bool> x) (Equal <typ.Bool> x))
(GreaterEqualNoov (InvertFlags x)) => (OR (LessThanNoov <typ.Bool> x) (Equal <typ.Bool> x))
(LessThanNoov (InvertFlags x)) => (CSEL0 [OpARM64NotEqual] (GreaterEqualNoov <typ.Bool> x) x)
(GreaterEqualNoov (InvertFlags x)) => (CSINC [OpARM64NotEqual] (LessThanNoov <typ.Bool> x) (MOVDconst [0]) x)
// Boolean-generating instructions (NOTE: NOT all boolean Values) always
// zero upper bit of the register; no need to zero-extend

18
src/cmd/compile/internal/ssa/bench_test.go
View file

@ -30,3 +30,21 @@ func BenchmarkPhioptPass(b *testing.B) {
}
}
}
type Point struct {
X, Y int
}
//go:noinline
func sign(p1, p2, p3 Point) bool {
return (p1.X-p3.X)*(p2.Y-p3.Y)-(p2.X-p3.X)*(p1.Y-p3.Y) < 0
}
func BenchmarkInvertLessThanNoov(b *testing.B) {
p1 := Point{1, 2}
p2 := Point{2, 3}
p3 := Point{3, 4}
for i := 0; i < b.N; i++ {
sign(p1, p2, p3)
}
}

20
src/cmd/compile/internal/ssa/rewriteARM64.go
View file

@ -5974,18 +5974,19 @@ func rewriteValueARM64_OpARM64GreaterEqualNoov(v *Value) bool {
b := v.Block
typ := &b.Func.Config.Types
// match: (GreaterEqualNoov (InvertFlags x))
// result: (OR (LessThanNoov <typ.Bool> x) (Equal <typ.Bool> x))
// result: (CSINC [OpARM64NotEqual] (LessThanNoov <typ.Bool> x) (MOVDconst [0]) x)
for {
if v_0.Op != OpARM64InvertFlags {
break
}
x := v_0.Args[0]
v.reset(OpARM64OR)
v.reset(OpARM64CSINC)
v.AuxInt = opToAuxInt(OpARM64NotEqual)
v0 := b.NewValue0(v.Pos, OpARM64LessThanNoov, typ.Bool)
v0.AddArg(x)
v1 := b.NewValue0(v.Pos, OpARM64Equal, typ.Bool)
v1.AddArg(x)
v.AddArg2(v0, v1)
v1 := b.NewValue0(v.Pos, OpARM64MOVDconst, typ.UInt64)
v1.AuxInt = int64ToAuxInt(0)
v.AddArg3(v0, v1, x)
return true
}
return false
@ -6709,18 +6710,17 @@ func rewriteValueARM64_OpARM64LessThanNoov(v *Value) bool {
b := v.Block
typ := &b.Func.Config.Types
// match: (LessThanNoov (InvertFlags x))
// result: (BIC (GreaterEqualNoov <typ.Bool> x) (Equal <typ.Bool> x))
// result: (CSEL0 [OpARM64NotEqual] (GreaterEqualNoov <typ.Bool> x) x)
for {
if v_0.Op != OpARM64InvertFlags {
break
}
x := v_0.Args[0]
v.reset(OpARM64BIC)
v.reset(OpARM64CSEL0)
v.AuxInt = opToAuxInt(OpARM64NotEqual)
v0 := b.NewValue0(v.Pos, OpARM64GreaterEqualNoov, typ.Bool)
v0.AddArg(x)
v1 := b.NewValue0(v.Pos, OpARM64Equal, typ.Bool)
v1.AddArg(x)
v.AddArg2(v0, v1)
v.AddArg2(v0, x)
return true
}
return false

13
test/codegen/comparisons.go
View file

@ -788,3 +788,16 @@ func cmp7() {
cmp5[string]("") // force instantiation
cmp6[string]("") // force instantiation
}
type Point struct {
X, Y int
}
// invertLessThanNoov checks (LessThanNoov (InvertFlags x)) is lowered as
// CMP, CSET, CSEL instruction sequence. InvertFlags are only generated under
// certain conditions, see canonLessThan, so if the code below does not
// generate an InvertFlags OP, this check may fail.
func invertLessThanNoov(p1, p2, p3 Point) bool {
// arm64:`CMP`,`CSET`,`CSEL`
return (p1.X-p3.X)*(p2.Y-p3.Y)-(p2.X-p3.X)*(p1.Y-p3.Y) < 0
}