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Diffstat (limited to 'lib/Transforms/Scalar/DCE.cpp')
-rw-r--r--lib/Transforms/Scalar/DCE.cpp88
1 files changed, 51 insertions, 37 deletions
diff --git a/lib/Transforms/Scalar/DCE.cpp b/lib/Transforms/Scalar/DCE.cpp
index 14ee8d5a6c..5bc3c5b089 100644
--- a/lib/Transforms/Scalar/DCE.cpp
+++ b/lib/Transforms/Scalar/DCE.cpp
@@ -61,7 +61,7 @@ static bool RemoveUnusedDefs(ValueHolder<ValueSubclass, ItemParentType> &Vals,
delete Vals.remove(DI);
Changed = true;
} else {
- DI++;
+ ++DI;
}
}
return Changed;
@@ -79,8 +79,8 @@ static bool RemoveSingularPHIs(BasicBlock *BB) {
if (PI == pred_end(BB) || ++PI != pred_end(BB))
return false; // More than one predecessor...
- Instruction *I = BB->getInstList().front();
- if (I->getInstType() != Instruction::PHINode) return false; // No PHI nodes
+ Instruction *I = BB->front();
+ if (!I->isPHINode()) return false; // No PHI nodes
//cerr << "Killing PHIs from " << BB;
//cerr << "Pred #0 = " << *pred_begin(BB);
@@ -93,10 +93,10 @@ static bool RemoveSingularPHIs(BasicBlock *BB) {
Value *V = PN->getOperand(0);
PN->replaceAllUsesWith(V); // Replace PHI node with its single value.
- delete BB->getInstList().remove(BB->getInstList().begin());
+ delete BB->getInstList().remove(BB->begin());
- I = BB->getInstList().front();
- } while (I->getInstType() == Instruction::PHINode);
+ I = BB->front();
+ } while (I->isPHINode());
return true; // Yes, we nuked at least one phi node
}
@@ -154,8 +154,8 @@ static void RemovePredecessorFromBlock(BasicBlock *BB, BasicBlock *Pred) {
// Okay, now we know that we need to remove predecessor #pred_idx from all
// PHI nodes. Iterate over each PHI node fixing them up
- BasicBlock::InstListType::iterator II(BB->getInstList().begin());
- for (; (*II)->getInstType() == Instruction::PHINode; ++II) {
+ BasicBlock::iterator II(BB->begin());
+ for (; (*II)->isPHINode(); ++II) {
PHINode *PN = (PHINode*)*II;
PN->removeIncomingValue(BB);
@@ -177,25 +177,36 @@ static void RemovePredecessorFromBlock(BasicBlock *BB, BasicBlock *Pred) {
// Assumption: BB is the single predecessor of Succ.
//
static void PropogatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
- assert(BB && Succ && *pred_begin(Succ) == BB && "BB is only pred of Succ" &&
- ++pred_begin(Succ) == pred_end(Succ));
+ assert(Succ->front()->isPHINode() && "Only works on PHId BBs!");
// If there is more than one predecessor, and there are PHI nodes in
// the successor, then we need to add incoming edges for the PHI nodes
- pred_iterator PI(pred_begin(BB));
- for (; PI != pred_end(BB); ++PI) {
- // TODO:
- }
+ //
+ const vector<BasicBlock*> BBPreds(pred_begin(BB), pred_end(BB));
+
+ BasicBlock::iterator I = Succ->begin();
+ do { // Loop over all of the PHI nodes in the successor BB
+ PHINode *PN = (PHINode*)*I;
+ Value *OldVal = PN->removeIncomingValue(BB);
+ assert(OldVal && "No entry in PHI for Pred BB!");
+
+ for (vector<BasicBlock*>::const_iterator PredI = BBPreds.begin(),
+ End = BBPreds.end(); PredI != End; ++PredI) {
+ // Add an incoming value for each of the new incoming values...
+ PN->addIncoming(OldVal, *PredI);
+ }
+
+ ++I;
+ } while ((*I)->isPHINode());
}
static bool DoDCEPass(Method *M) {
- Method::BasicBlocksType &BBs = M->getBasicBlocks();
- Method::BasicBlocksType::iterator BBIt, BBEnd = BBs.end();
- if (BBs.begin() == BBEnd) return false; // Nothing to do
+ Method::iterator BBIt, BBEnd = M->end();
+ if (M->begin() == BBEnd) return false; // Nothing to do
bool Changed = false;
// Loop through now and remove instructions that have no uses...
- for (BBIt = BBs.begin(); BBIt != BBEnd; BBIt++) {
+ for (BBIt = M->begin(); BBIt != BBEnd; ++BBIt) {
Changed |= RemoveUnusedDefs((*BBIt)->getInstList(), BasicBlockDCE());
Changed |= RemoveSingularPHIs(*BBIt);
}
@@ -203,11 +214,11 @@ static bool DoDCEPass(Method *M) {
// Loop over all of the basic blocks (except the first one) and remove them
// if they are unneeded...
//
- for (BBIt = BBs.begin(), ++BBIt; BBIt != BBs.end(); ++BBIt) {
+ for (BBIt = M->begin(), ++BBIt; BBIt != M->end(); ++BBIt) {
BasicBlock *BB = *BBIt;
assert(BB->getTerminator() && "Degenerate basic block encountered!");
-#if 0
+#if 0 // This is know to basically work?
// Remove basic blocks that have no predecessors... which are unreachable.
if (pred_begin(BB) == pred_end(BB) &&
!BB->hasConstantPoolReferences() && 0) {
@@ -215,43 +226,46 @@ static bool DoDCEPass(Method *M) {
// Loop through all of our successors and make sure they know that one
// of their predecessors is going away.
- for (succ_iterator SI = succ_begin(BB), EI = succ_end(BB); SI != EI; ++SI)
- RemovePredecessorFromBlock(*SI, BB);
+ for_each(succ_begin(BB), succ_end(BB),
+ bind_2nd(RemovePredecessorFromBlock, BB));
- while (!BB->getInstList().empty()) {
- Instruction *I = BB->getInstList().front();
+ while (!BB->empty()) {
+ Instruction *I = BB->front();
// If this instruction is used, replace uses with an arbitrary
// constant value. Because control flow can't get here, we don't care
// what we replace the value with.
if (!I->use_empty()) ReplaceUsesWithConstant(I);
// Remove the instruction from the basic block
- delete BB->getInstList().remove(BB->getInstList().begin());
+ delete BB->getInstList().remove(BB->begin());
}
- delete BBs.remove(BBIt);
+ delete M->getBasicBlocks().remove(BBIt);
--BBIt; // remove puts use on the next block, we want the previous one
Changed = true;
continue;
}
+#endif
+#if 0 // This has problems
// Check to see if this block has no instructions and only a single
// successor. If so, replace block references with successor.
succ_iterator SI(succ_begin(BB));
if (SI != succ_end(BB) && ++SI == succ_end(BB)) { // One succ?
- Instruction *I = BB->getInstList().front();
+ Instruction *I = BB->front();
if (I->isTerminator()) { // Terminator is the only instruction!
+ BasicBlock *Succ = *succ_begin(BB); // There is exactly one successor
+ cerr << "Killing Trivial BB: \n" << BB;
- if (Succ->getInstList().front()->getInstType() == Instruction::PHINode){
- // Add entries to the PHI nodes so that the PHI nodes have the right
- // number of entries...
+ if (Succ->front()->isPHINode()) {
+ // If our successor has PHI nodes, then we need to update them to
+ // include entries for BB's predecessors, not for BB itself.
+ //
PropogatePredecessorsForPHIs(BB, Succ);
}
- BasicBlock *Succ = *succ_begin(BB); // There is exactly one successor
BB->replaceAllUsesWith(Succ);
- cerr << "Killing Trivial BB: \n" << BB;
- BB = BBs.remove(BBIt);
+ BB = M->getBasicBlocks().remove(BBIt);
--BBIt; // remove puts use on the next block, we want the previous one
if (BB->hasName() && !Succ->hasName()) // Transfer name if we can
@@ -280,21 +294,21 @@ static bool DoDCEPass(Method *M) {
//cerr << "Merging: " << BB << "into: " << Pred;
// Delete the unconditianal branch from the predecessor...
- BasicBlock::InstListType::iterator DI = Pred->getInstList().end();
+ BasicBlock::iterator DI = Pred->end();
assert(Pred->getTerminator() &&
"Degenerate basic block encountered!"); // Empty bb???
delete Pred->getInstList().remove(--DI); // Destroy uncond branch
// Move all definitions in the succecessor to the predecessor...
- while (!BB->getInstList().empty()) {
- DI = BB->getInstList().begin();
+ while (!BB->empty()) {
+ DI = BB->begin();
Instruction *Def = BB->getInstList().remove(DI); // Remove from front
Pred->getInstList().push_back(Def); // Add to end...
}
// Remove basic block from the method... and advance iterator to the
// next valid block...
- BB = BBs.remove(BBIt);
+ BB = M->getBasicBlocks().remove(BBIt);
--BBIt; // remove puts us on the NEXT bb. We want the prev BB
Changed = true;
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2025-04-28 18:53:20 +0000