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refactor critical edge breaking out into the SplitCritEdgesForPHIConstants method. 

This is a baby step towards fixing PR925.

llvm-svn: 30643
This commit is contained in:
Chris Lattner 2006-09-28 06:17:10 +00:00
parent 3cbd1604f8
commit a9caf95591
2 changed files with 21 additions and 9 deletions
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1
llvm/include/llvm/CodeGen/SelectionDAGISel.h
View File

@ -124,6 +124,7 @@ protected:
SelectionDAG &DAG); SelectionDAG &DAG);
private: private:
void SplitCritEdgesForPHIConstants(BasicBlock *BB);
SDOperand CopyValueToVirtualRegister(SelectionDAGLowering &SDL, SDOperand CopyValueToVirtualRegister(SelectionDAGLowering &SDL,
Value *V, unsigned Reg); Value *V, unsigned Reg);
void SelectBasicBlock(BasicBlock *BB, MachineFunction &MF, void SelectBasicBlock(BasicBlock *BB, MachineFunction &MF,

29
llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
View File

@ -845,8 +845,6 @@ void SelectionDAGLowering::visitSwitchCase(SelectionDAGISel::CaseBlock &CB) {
CurMBB->addSuccessor(CB.RHSBB); CurMBB->addSuccessor(CB.RHSBB);
} }
/// visitSwitchCase - Emits the necessary code to represent a single node in
/// the binary search tree resulting from lowering a switch instruction.
void SelectionDAGLowering::visitJumpTable(SelectionDAGISel::JumpTable &JT) { void SelectionDAGLowering::visitJumpTable(SelectionDAGISel::JumpTable &JT) {
// FIXME: Need to emit different code for PIC vs. Non-PIC, specifically, // FIXME: Need to emit different code for PIC vs. Non-PIC, specifically,
// we need to add the address of the jump table to the value loaded, since // we need to add the address of the jump table to the value loaded, since
@ -3207,6 +3205,21 @@ static bool OptimizeGEPExpression(GetElementPtrInst *GEPI,
return true; return true;
} }
/// SplitCritEdgesForPHIConstants - If this block has any PHI nodes with
/// constant operands, and if any of the edges feeding the PHI node are
/// critical, split them so that the assignments of a constant to a register
/// will not be executed on a path that isn't relevant.
void SelectionDAGISel::SplitCritEdgesForPHIConstants(BasicBlock *BB) {
PHINode *PN;
BasicBlock::iterator BBI = BB->begin();
while ((PN = dyn_cast<PHINode>(BBI++))) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (isa<Constant>(PN->getIncomingValue(i)))
SplitCriticalEdge(PN->getIncomingBlock(i), BB);
}
}
bool SelectionDAGISel::runOnFunction(Function &Fn) { bool SelectionDAGISel::runOnFunction(Function &Fn) {
MachineFunction &MF = MachineFunction::construct(&Fn, TLI.getTargetMachine()); MachineFunction &MF = MachineFunction::construct(&Fn, TLI.getTargetMachine());
RegMap = MF.getSSARegMap(); RegMap = MF.getSSARegMap();
@ -3225,14 +3238,12 @@ bool SelectionDAGISel::runOnFunction(Function &Fn) {
while (MadeChange) { while (MadeChange) {
MadeChange = false; MadeChange = false;
for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) { for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
PHINode *PN; // If this block has any PHI nodes with constant operands, and if any of the
BasicBlock::iterator BBI; // edges feeding the PHI node are critical, split them.
for (BBI = BB->begin(); (PN = dyn_cast<PHINode>(BBI)); ++BBI) if (isa<PHINode>(BB->begin()))
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) SplitCritEdgesForPHIConstants(BB);
if (isa<Constant>(PN->getIncomingValue(i)))
SplitCriticalEdge(PN->getIncomingBlock(i), BB);
for (BasicBlock::iterator E = BB->end(); BBI != E; ) { for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
Instruction *I = BBI++; Instruction *I = BBI++;
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
MadeChange |= OptimizeGEPExpression(GEPI, TLI.getTargetData()); MadeChange |= OptimizeGEPExpression(GEPI, TLI.getTargetData());