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pass_phielim.go
54 lines (47 loc) · 1.53 KB
/
pass_phielim.go
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/*
* Copyright 2022 ByteDance Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package ssa
// PhiElim replaces Phi nodes that are essentially copies with actual copy operaions.
type PhiElim struct{}
func (PhiElim) Apply(cfg *CFG) {
cfg.PostOrder().ForEach(func(bb *BasicBlock) {
phi := bb.Phi
bb.Phi = bb.Phi[:0]
/* scan every Phi node */
for _, v := range phi {
ok := true
rr := Reg(0)
/* get one of the registers */
for _, r := range v.V {
rr = *r
break
}
/* check for Phi node */
for _, r := range v.V {
if rr != *r {
ok = false
break
}
}
/* replace the Phi node with a copy operation if needed */
if !ok {
bb.Phi = append(bb.Phi, v)
} else {
bb.Ins = append([]IrNode { IrCopy(v.R, rr) }, bb.Ins...)
}
}
})
}