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add an argument to allow avoiding deleting phi nodes. 

llvm-svn: 21255
This commit is contained in:
Chris Lattner 2005-04-12 18:52:14 +00:00
parent eb958b0e45
commit 9daef352e9
1 changed files with 9 additions and 6 deletions
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15
llvm/lib/VMCore/BasicBlock.cpp
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@ -12,7 +12,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/BasicBlock.h"
#include "llvm/Constant.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
#include "llvm/Support/CFG.h"
@ -134,7 +134,8 @@ BasicBlock *BasicBlock::getSinglePredecessor() {
// update the PHI nodes that reside in the block. Note that this should be
// called while the predecessor still refers to this block.
//
void BasicBlock::removePredecessor(BasicBlock *Pred) {
void BasicBlock::removePredecessor(BasicBlock *Pred,
bool DontDeleteUselessPHIs) {
assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
"removePredecessor: BB is not a predecessor!");
@ -164,10 +165,12 @@ void BasicBlock::removePredecessor(BasicBlock *Pred) {
if (this == Other) max_idx = 3;
}
if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
// <= Two predecessors BEFORE I remove one?
if (max_idx <= 2 && !DontDeleteUselessPHIs) {
// Yup, loop through and nuke the PHI nodes
while (PHINode *PN = dyn_cast<PHINode>(&front())) {
PN->removeIncomingValue(Pred); // Remove the predecessor first...
// Remove the predecessor first.
PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);
// If the PHI _HAD_ two uses, replace PHI node with its now *single* value
if (max_idx == 2) {
@ -175,7 +178,7 @@ void BasicBlock::removePredecessor(BasicBlock *Pred) {
PN->replaceAllUsesWith(PN->getOperand(0));
else
// We are left with an infinite loop with no entries: kill the PHI.
PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
getInstList().pop_front(); // Remove the PHI node
}
@ -187,7 +190,7 @@ void BasicBlock::removePredecessor(BasicBlock *Pred) {
// PHI nodes. Iterate over each PHI node fixing them up
PHINode *PN;
for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ++II)
PN->removeIncomingValue(Pred);
PN->removeIncomingValue(Pred, false);
}
}