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LocalMultiStore: Always put varId for backedge on loop phi function.

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And always patch the backedge operand when patching phi functions. This
approach is more correct and cleaner. The previous code was generating
incorrect phis when the backedge block had no predecessors.
This commit is contained in:
Greg Fischer 2017-07-11 16:52:19 -06:00 committed by David Neto
parent e2544ddc90
commit fe24e0316f
1 changed files with 9 additions and 11 deletions
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20
source/opt/local_ssa_elim_pass.cpp
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@ -460,7 +460,7 @@ void LocalMultiStoreElimPass::SSABlockInitLoopHeader(
continue;
}
// Val differs across predecessors. Add phi op to block and
// add its result id to the map. For live back edge predecessor,
// add its result id to the map. For back edge predecessor,
// use the variable id. We will patch this after visiting back
// edge predecessor. For predecessors that do not define a value,
// use undef.
@ -469,10 +469,7 @@ void LocalMultiStoreElimPass::SSABlockInitLoopHeader(
for (uint32_t predLabel : label2preds_[label]) {
uint32_t valId;
if (predLabel == backLabel) {
if (val0Id == 0)
valId = varId;
else
valId = Type2Undef(typeId);
valId = varId;
}
else {
const auto var_val_itr = label2ssa_map_[predLabel].find(varId);
@ -594,14 +591,15 @@ void LocalMultiStoreElimPass::PatchPhis(uint32_t header_id, uint32_t back_id) {
if (cnt % 2 == 1 && *iid == back_id) idx = cnt - 1;
++cnt;
});
// Only patch operands that are in the backedge predecessor map
// Use undef if variable not in backedge predecessor map
const uint32_t varId = phiItr->GetSingleWordInOperand(idx);
const auto valItr = label2ssa_map_[back_id].find(varId);
if (valItr != label2ssa_map_[back_id].end()) {
phiItr->SetInOperand(idx, { valItr->second });
// Analyze uses now that they are complete
def_use_mgr_->AnalyzeInstUse(&*phiItr);
}
uint32_t valId = (valItr != label2ssa_map_[back_id].end()) ?
valItr->second :
Type2Undef(GetPointeeTypeId(def_use_mgr_->GetDef(varId)));
phiItr->SetInOperand(idx, { valId });
// Analyze uses now that they are complete
def_use_mgr_->AnalyzeInstUse(&*phiItr);
}
}