// Remove the CFG edge between |pred| and |block|, after releasing the phi
// operands on that edge and discarding any definitions consequently made dead.
bool
ValueNumberer::removePredecessorAndDoDCE(MBasicBlock* block, MBasicBlock* pred, size_t predIndex)
{
MOZ_ASSERT(!block->isMarked(),
"Block marked unreachable should have predecessors removed already");
// Before removing the predecessor edge, scan the phi operands for that edge
// for dead code before they get removed.
MOZ_ASSERT(nextDef_ == nullptr);
for (MPhiIterator iter(block->phisBegin()), end(block->phisEnd()); iter != end; ) {
MPhi* phi = *iter++;
MOZ_ASSERT(!values_.has(phi), "Visited phi in block having predecessor removed");
MOZ_ASSERT(!phi->isGuard());
MDefinition* op = phi->getOperand(predIndex);
phi->removeOperand(predIndex);
nextDef_ = iter != end ? *iter : nullptr;
if (!handleUseReleased(op, DontSetUseRemoved) || !processDeadDefs())
return false;
// If |nextDef_| became dead while we had it pinned, advance the
// iterator and discard it now.
while (nextDef_ && !nextDef_->hasUses() && !nextDef_->isGuardRangeBailouts()) {
phi = nextDef_->toPhi();
iter++;
nextDef_ = iter != end ? *iter : nullptr;
if (!discardDefsRecursively(phi))
return false;
}
}
nextDef_ = nullptr;
block->removePredecessorWithoutPhiOperands(pred, predIndex);
return true;
}
