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Fix bug: test/Regression/Transforms/CFGSimplify/2002-05-21-PHIElimination.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2694 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-05-21 19:52:49 +00:00
parent 4a4e39d647
commit 87a09b10f8
1 changed files with 21 additions and 4 deletions
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25
lib/VMCore/BasicBlock.cpp
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@ -100,8 +100,26 @@ void BasicBlock::removePredecessor(BasicBlock *Pred) {
for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
// If there are exactly two predecessors, then we want to nuke the PHI nodes
// altogether.
// altogether. We cannot do this, however if this in this case however:
//
// Loop:
// %x = phi [X, Loop]
// %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
// br Loop ;; %x2 does not dominate all uses
//
// This is because the PHI node input is actually taken from the predecessor
// basic block. The only case this can happen is with a self loop, so we
// check for this case explicitly now.
//
assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
if (max_idx == 2) {
PI = pred_begin(this);
BasicBlock *Other = *PI == Pred ? *++PI : *PI;
// Disable PHI elimination!
if (this == Other) max_idx = 3;
}
if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
// Yup, loop through and nuke the PHI nodes
while (PHINode *PN = dyn_cast<PHINode>(front())) {
@ -118,9 +136,8 @@ void BasicBlock::removePredecessor(BasicBlock *Pred) {
} else {
// Okay, now we know that we need to remove predecessor #pred_idx from all
// PHI nodes. Iterate over each PHI node fixing them up
iterator II(begin());
for (; isa<PHINode>(*II); ++II)
cast<PHINode>(*II)->removeIncomingValue(Pred);
for (iterator II = begin(); PHINode *PN = dyn_cast<PHINode>(*II); ++II)
PN->removeIncomingValue(Pred);
}
}