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cmd/compile: avoid the use of XOR for boolean equality on riscv64

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The use of SEQZ/SNEZ and SUB allows for other optimisations to be utilised,
particularly absorption into branch equality conditions.

Change-Id: I74e7d6a07a8decc1bdb651660c322bcc6eb6a10a
Reviewed-on: https://go-review.googlesource.com/c/go/+/428216
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Meng Zhuo <mzh@golangcn.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Joel Sing 2022-08-30 18:59:53 +10:00
parent fd82718e06
commit 83d94daec2
2 changed files with 22 additions and 6 deletions
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4
src/cmd/compile/internal/ssa/gen/RISCV64.rules
View File

@ -534,8 +534,8 @@
// Boolean ops; 0=false, 1=true
(AndB ...) => (AND ...)
(OrB ...) => (OR ...)
(EqB x y) => (SEQZ (XOR <typ.Bool> x y))
(NeqB ...) => (XOR ...)
(EqB x y) => (SEQZ (SUB <typ.Bool> x y))
(NeqB x y) => (SNEZ (SUB <typ.Bool> x y))
(Not ...) => (SEQZ ...)
// Lowering pointer arithmetic

24
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -406,8 +406,7 @@ func rewriteValueRISCV64(v *Value) bool {
case OpNeq8:
return rewriteValueRISCV64_OpNeq8(v)
case OpNeqB:
v.Op = OpRISCV64XOR
return true
return rewriteValueRISCV64_OpNeqB(v)
case OpNeqPtr:
return rewriteValueRISCV64_OpNeqPtr(v)
case OpNilCheck:
@ -1121,12 +1120,12 @@ func rewriteValueRISCV64_OpEqB(v *Value) bool {
b := v.Block
typ := &b.Func.Config.Types
// match: (EqB x y)
// result: (SEQZ (XOR <typ.Bool> x y))
// result: (SEQZ (SUB <typ.Bool> x y))
for {
x := v_0
y := v_1
v.reset(OpRISCV64SEQZ)
v0 := b.NewValue0(v.Pos, OpRISCV64XOR, typ.Bool)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, typ.Bool)
v0.AddArg2(x, y)
v.AddArg(v0)
return true
@ -2970,6 +2969,23 @@ func rewriteValueRISCV64_OpNeq8(v *Value) bool {
return true
}
}
func rewriteValueRISCV64_OpNeqB(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
// match: (NeqB x y)
// result: (SNEZ (SUB <typ.Bool> x y))
for {
x := v_0
y := v_1
v.reset(OpRISCV64SNEZ)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, typ.Bool)
v0.AddArg2(x, y)
v.AddArg(v0)
return true
}
}
func rewriteValueRISCV64_OpNeqPtr(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]