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cmd/compile: fold negation into subtraction on riscv64 

Fold negation into subtraction and avoid double negation.

This removes around 500 instructions from the Go binary on riscv64.

Change-Id: I4aac6c87baa2a0759b180ba87876d488a23df6d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/431105
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Joedian Reid <joedian@golang.org>
Reviewed-by: Wayne Zuo <wdvxdr@golangcn.org>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Joel Sing 2022-09-09 23:15:46 +10:00
parent ba8c94b5f2
commit 4274ffd4b8
2 changed files with 56 additions and 0 deletions
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7
src/cmd/compile/internal/ssa/_gen/RISCV64.rules
View File

@ -778,6 +778,13 @@
(SUB (MOVDconst [0]) x) => (NEG x)
(SUBW (MOVDconst [0]) x) => (NEGW x)
// Fold negation into subtraction.
(NEG (SUB x y)) => (SUB y x)
(NEG <t> s:(ADDI [val] (SUB x y))) && s.Uses == 1 && is32Bit(-val) => (ADDI [-val] (SUB <t> y x))
// Double negation.
(NEG (NEG x)) => x
// Addition of zero or two constants.
(ADDI [0] x) => x
(ADDI [x] (MOVDconst [y])) && is32Bit(x + y) => (MOVDconst [x + y])

49
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -5437,6 +5437,55 @@ func rewriteValueRISCV64_OpRISCV64MOVWstorezero(v *Value) bool {
}
func rewriteValueRISCV64_OpRISCV64NEG(v *Value) bool {
v_0 := v.Args[0]
b := v.Block
// match: (NEG (SUB x y))
// result: (SUB y x)
for {
if v_0.Op != OpRISCV64SUB {
break
}
y := v_0.Args[1]
x := v_0.Args[0]
v.reset(OpRISCV64SUB)
v.AddArg2(y, x)
return true
}
// match: (NEG <t> s:(ADDI [val] (SUB x y)))
// cond: s.Uses == 1 && is32Bit(-val)
// result: (ADDI [-val] (SUB <t> y x))
for {
t := v.Type
s := v_0
if s.Op != OpRISCV64ADDI {
break
}
val := auxIntToInt64(s.AuxInt)
s_0 := s.Args[0]
if s_0.Op != OpRISCV64SUB {
break
}
y := s_0.Args[1]
x := s_0.Args[0]
if !(s.Uses == 1 && is32Bit(-val)) {
break
}
v.reset(OpRISCV64ADDI)
v.AuxInt = int64ToAuxInt(-val)
v0 := b.NewValue0(v.Pos, OpRISCV64SUB, t)
v0.AddArg2(y, x)
v.AddArg(v0)
return true
}
// match: (NEG (NEG x))
// result: x
for {
if v_0.Op != OpRISCV64NEG {
break
}
x := v_0.Args[0]
v.copyOf(x)
return true
}
// match: (NEG (MOVDconst [x]))
// result: (MOVDconst [-x])
for {