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Fix a problem where the legalizer would run out of stack space on extremely 

large basic blocks because it was purely recursive.  This switches it to an
iterative/recursive hybrid.

llvm-svn: 23596
This commit is contained in:
Chris Lattner 2005-10-02 17:49:46 +00:00
parent 7f718e61e8
commit 9cfccfb517
1 changed files with 36 additions and 9 deletions
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45
llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
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@ -380,8 +380,43 @@ SDOperand SelectionDAGLegalize::PromoteLegalFP_TO_INT(SDOperand LegalOp,
void SelectionDAGLegalize::LegalizeDAG() {
// The legalize process is inherently a bottom-up recursive process (users
// legalize their uses before themselves). Given infinite stack space, we
// could just start legalizing on the root and traverse the whole graph. In
// practice however, this causes us to run out of stack space on large basic
// blocks. To avoid this problem, legalize the entry node, then all its uses
// iteratively instead of recursively.
std::vector<SDOperand> Worklist;
Worklist.push_back(DAG.getEntryNode());
while (!Worklist.empty()) {
SDOperand Node = Worklist.back();
Worklist.pop_back();
if (LegalizedNodes.count(Node)) continue;
for (SDNode::use_iterator UI = Node.Val->use_begin(),
E = Node.Val->use_end(); UI != E; ++UI) {
// Scan the values. If this use has a value that is a token chain, add it
// to the worklist.
SDNode *User = *UI;
for (unsigned i = 0, e = User->getNumValues(); i != e; ++i)
if (User->getValueType(i) == MVT::Other) {
Worklist.push_back(SDOperand(User, i));
break;
}
}
// Finally, legalize this node.
LegalizeOp(Node);
}
// Finally, legalize from the root up, to make sure we have legalized
// everything possible.
SDOperand OldRoot = DAG.getRoot();
SDOperand NewRoot = LegalizeOp(OldRoot);
DAG.setRoot(NewRoot);
ExpandedNodes.clear();
@ -588,17 +623,9 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) {
Tmp1 = LegalizeOp(Node->getOperand(0)); // Legalize the chain.
// Do not try to legalize the target-specific arguments (#1+)
Tmp2 = Node->getOperand(0);
if (Tmp1 != Tmp2) {
if (Tmp1 != Tmp2)
Node->setAdjCallChain(Tmp1);
// If moving the operand from pointing to Tmp2 dropped its use count to 1,
// this will cause the maps used to memoize results to get confused.
// Create and add a dummy use, just to increase its use count. This will
// be removed at the end of legalize when dead nodes are removed.
if (Tmp2.Val->hasOneUse())
DAG.getNode(ISD::PCMARKER, MVT::Other, Tmp2,
DAG.getConstant(0, MVT::i32));
}
// Note that we do not create new CALLSEQ_DOWN/UP nodes here. These
// nodes are treated specially and are mutated in place. This makes the dag
// legalization process more efficient and also makes libcall insertion