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Avoid copying flow-sensitive state when only a goto separates blocks.

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BUG=
R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/48353007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18090 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
titzer@chromium.org 2013-11-27 07:13:00 +00:00
parent b558a10c67
commit ddb4ad853b
1 changed files with 9 additions and 2 deletions
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11
src/hydrogen-flow-engine.h
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@ -138,12 +138,19 @@ class HFlowEngine {
}
// Propagate the block state forward to all successor blocks.
for (int i = 0; i < block->end()->SuccessorCount(); i++) {
int max = block->end()->SuccessorCount();
for (int i = 0; i < max; i++) {
HBasicBlock* succ = block->end()->SuccessorAt(i);
IncrementPredecessorCount(succ);
if (StateAt(succ) == NULL) {
// This is the first state to reach the successor.
SetStateAt(succ, state->Copy(succ, zone_));
if (max == 1 && succ->predecessors()->length() == 1) {
// Optimization: successor can inherit this state.
SetStateAt(succ, state);
} else {
// Successor needs a copy of the state.
SetStateAt(succ, state->Copy(succ, zone_));
}
} else {
// Merge the current state with the state already at the successor.
SetStateAt(succ, state->Merge(succ, StateAt(succ), zone_));