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regalloc: simplifies livenessAnalysis/finalizeStartReg #2256

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Jun 17, 2024
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regalloc: simplifies livenessAnalysis/finalizeStartReg #2256

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9 changes: 3 additions & 6 deletions internal/engine/wazevo/backend/regalloc/regalloc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -392,17 +392,15 @@ const (
// The algorithm here is described in https://pfalcon.github.io/ssabook/latest/book-full.pdf Chapter 9.2.
func (a *Allocator) livenessAnalysis(f Function) {
s := &a.state
for blk := f.PostOrderBlockIteratorBegin(); blk != nil; blk = f.PostOrderBlockIteratorNext() { // Order doesn't matter.

for blk := f.PostOrderBlockIteratorBegin(); blk != nil; blk = f.PostOrderBlockIteratorNext() {
// We should gather phi value data.
for _, p := range blk.BlockParams(&a.vs) {
vs := s.getVRegState(p.ID())
vs.isPhi = true
vs.defBlk = blk
}
}

for blk := f.PostOrderBlockIteratorBegin(); blk != nil; blk = f.PostOrderBlockIteratorNext() {
blkID := blk.ID()
info := a.getOrAllocateBlockState(blkID)

Expand Down Expand Up @@ -587,15 +585,14 @@ func (a *Allocator) updateLiveInVRState(liveness *blockState) {

func (a *Allocator) finalizeStartReg(blk Block) {
bID := blk.ID()
liveness := a.getOrAllocateBlockState(bID)
s := &a.state
currentBlkState := a.getOrAllocateBlockState(bID)
if currentBlkState.startFromPredIndex > -1 {
return
}

s.currentBlockID = bID
a.updateLiveInVRState(liveness)
a.updateLiveInVRState(currentBlkState)

preds := blk.Preds()
var predState *blockState
Expand Down Expand Up @@ -624,7 +621,7 @@ func (a *Allocator) finalizeStartReg(blk Block) {
s.useRealReg(u.RealReg(), u)
}
currentBlkState.startFromPredIndex = 0
} else if predState != nil {
} else {
if wazevoapi.RegAllocLoggingEnabled {
fmt.Printf("allocating blk%d starting from blk%d (on index=%d) \n",
bID, blk.Pred(currentBlkState.startFromPredIndex).ID(), currentBlkState.startFromPredIndex)
Expand Down
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