void
MBasicBlock::inheritPhis(MBasicBlock* header)
{
MResumePoint* headerRp = header->entryResumePoint();
size_t stackDepth = headerRp->stackDepth();
for (size_t slot = 0; slot < stackDepth; slot++) {
MDefinition* exitDef = getSlot(slot);
MDefinition* loopDef = headerRp->getOperand(slot);
if (loopDef->block() != header) {
MOZ_ASSERT(loopDef->block()->id() < header->id());
MOZ_ASSERT(loopDef == exitDef);
continue;
}
// Phis are allocated by NewPendingLoopHeader.
MPhi* phi = loopDef->toPhi();
MOZ_ASSERT(phi->numOperands() == 2);
// The entry definition is always the leftmost input to the phi.
MDefinition* entryDef = phi->getOperand(0);
if (entryDef != exitDef)
continue;
// If the entryDef is the same as exitDef, then we must propagate the
// phi down to this successor. This chance was missed as part of
// setBackedge() because exits are not captured in resume points.
setSlot(slot, phi);
}
}
MBasicBlock*
MBasicBlock::NewSplitEdge(MIRGraph& graph, MBasicBlock* pred, size_t predEdgeIdx, MBasicBlock* succ)
{
MBasicBlock* split = nullptr;
if (!succ->pc()) {
// The predecessor does not have a PC, this is a Wasm compilation.
split = MBasicBlock::New(graph, succ->info(), pred, SPLIT_EDGE);
if (!split)
return nullptr;
} else {
// The predecessor has a PC, this is an IonBuilder compilation.
MResumePoint* succEntry = succ->entryResumePoint();
BytecodeSite* site = new(graph.alloc()) BytecodeSite(succ->trackedTree(), succEntry->pc());
split = new(graph.alloc()) MBasicBlock(graph, succ->info(), site, SPLIT_EDGE);
if (!split->init())
return nullptr;
// A split edge is used to simplify the graph to avoid having a
// predecessor with multiple successors as well as a successor with
// multiple predecessors. As instructions can be moved in this
// split-edge block, we need to give this block a resume point. To do
// so, we copy the entry resume points of the successor and filter the
// phis to keep inputs from the current edge.
// Propagate the caller resume point from the inherited block.
split->callerResumePoint_ = succ->callerResumePoint();
// Split-edge are created after the interpreter stack emulation. Thus,
// there is no need for creating slots.
split->stackPosition_ = succEntry->stackDepth();
// Create a resume point using our initial stack position.
MResumePoint* splitEntry = new(graph.alloc()) MResumePoint(split, succEntry->pc(),
MResumePoint::ResumeAt);
if (!splitEntry->init(graph.alloc()))
return nullptr;
split->entryResumePoint_ = splitEntry;
// The target entry resume point might have phi operands, keep the
// operands of the phi coming from our edge.
size_t succEdgeIdx = succ->indexForPredecessor(pred);
for (size_t i = 0, e = splitEntry->numOperands(); i < e; i++) {
MDefinition* def = succEntry->getOperand(i);
// This early in the pipeline, we have no recover instructions in
// any entry resume point.
MOZ_ASSERT_IF(def->block() == succ, def->isPhi());
if (def->block() == succ)
def = def->toPhi()->getOperand(succEdgeIdx);
splitEntry->initOperand(i, def);
}
// This is done in the New variant for wasm, so we cannot keep this
// line below, where the rest of the graph is modified.
if (!split->predecessors_.append(pred))
return nullptr;
}
split->setLoopDepth(succ->loopDepth());
// Insert the split edge block in-between.
split->end(MGoto::New(graph.alloc(), succ));
graph.insertBlockAfter(pred, split);
pred->replaceSuccessor(predEdgeIdx, split);
succ->replacePredecessor(pred, split);
return split;
}
