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cmd/compile: optimize subtraction of zero on riscv64

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Change-Id: I9a994b01e9fecb13077c30df4b7677d40d179cce
Reviewed-on: https://go-review.googlesource.com/c/go/+/221681
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Joel Sing 2020-03-02 04:24:35 +11:00
parent bd6f4cd886
commit d28b8524a4
2 changed files with 68 additions and 0 deletions
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9
src/cmd/compile/internal/ssa/gen/RISCV64.rules
View File

@ -467,5 +467,14 @@
(SUB x (MOVWconst [val])) && is32Bit(-val) -> (ADDI [-val] x)
(SUB x (MOVDconst [val])) && is32Bit(-val) -> (ADDI [-val] x)
// Subtraction of zero.
(SUB x (MOVBconst [0])) -> x
(SUB x (MOVHconst [0])) -> x
(SUB x (MOVWconst [0])) -> x
(SUB x (MOVDconst [0])) -> x
// Subtraction of zero with sign extension.
(SUBW x (MOVWconst [0])) -> (ADDIW [0] x)
// remove redundant *const ops
(ADDI [0] x) -> x

59
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -406,6 +406,8 @@ func rewriteValueRISCV64(v *Value) bool {
return rewriteValueRISCV64_OpRISCV64MOVWstore(v)
case OpRISCV64SUB:
return rewriteValueRISCV64_OpRISCV64SUB(v)
case OpRISCV64SUBW:
return rewriteValueRISCV64_OpRISCV64SUBW(v)
case OpRotateLeft16:
return rewriteValueRISCV64_OpRotateLeft16(v)
case OpRotateLeft32:
@ -2950,6 +2952,63 @@ func rewriteValueRISCV64_OpRISCV64SUB(v *Value) bool {
v.AddArg(x)
return true
}
// match: (SUB x (MOVBconst [0]))
// result: x
for {
x := v_0
if v_1.Op != OpRISCV64MOVBconst || v_1.AuxInt != 0 {
break
}
v.copyOf(x)
return true
}
// match: (SUB x (MOVHconst [0]))
// result: x
for {
x := v_0
if v_1.Op != OpRISCV64MOVHconst || v_1.AuxInt != 0 {
break
}
v.copyOf(x)
return true
}
// match: (SUB x (MOVWconst [0]))
// result: x
for {
x := v_0
if v_1.Op != OpRISCV64MOVWconst || v_1.AuxInt != 0 {
break
}
v.copyOf(x)
return true
}
// match: (SUB x (MOVDconst [0]))
// result: x
for {
x := v_0
if v_1.Op != OpRISCV64MOVDconst || v_1.AuxInt != 0 {
break
}
v.copyOf(x)
return true
}
return false
}
func rewriteValueRISCV64_OpRISCV64SUBW(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
// match: (SUBW x (MOVWconst [0]))
// result: (ADDIW [0] x)
for {
x := v_0
if v_1.Op != OpRISCV64MOVWconst || v_1.AuxInt != 0 {
break
}
v.reset(OpRISCV64ADDIW)
v.AuxInt = 0
v.AddArg(x)
return true
}
return false
}
func rewriteValueRISCV64_OpRotateLeft16(v *Value) bool {