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Refactor code a bit to make it simpler and eliminate the goto

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12888 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-04-13 15:21:18 +00:00
parent 6491340bc1
commit 1f62f82b05
1 changed files with 31 additions and 27 deletions
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58
lib/Transforms/Utils/LoopSimplify.cpp
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@ -469,6 +469,28 @@ static void VerifyExitBlocks(Loop *L) {
VerifyExitBlocks(*I);
}
/// FindPHIToPartitionLoops - The first part of loop-nestification is to find a
/// PHI node that tells us how to partition the loops.
static PHINode *FindPHIToPartitionLoops(Loop *L) {
for (BasicBlock::iterator I = L->getHeader()->begin();
PHINode *PN = dyn_cast<PHINode>(I); ) {
++I;
if (Value *V = hasConstantValue(PN)) {
// This is a degenerate PHI already, don't modify it!
PN->replaceAllUsesWith(V);
PN->getParent()->getInstList().erase(PN);
} else {
// Scan this PHI node looking for a use of the PHI node by itself.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == PN &&
L->contains(PN->getIncomingBlock(i)))
// We found something tasty to remove.
return PN;
}
}
return 0;
}
/// SeparateNestedLoop - If this loop has multiple backedges, try to pull one of
/// them out into a nested loop. This is important for code that looks like
/// this:
@ -488,36 +510,18 @@ static void VerifyExitBlocks(Loop *L) {
///
Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
BasicBlock *Header = L->getHeader();
PHINode *PN = FindPHIToPartitionLoops(L);
if (PN == 0) return 0; // No known way to partition.
// Pull out all predecessors that have varying values in the loop. This
// handles the case when a PHI node has multiple instances of itself as
// arguments.
std::vector<BasicBlock*> OuterLoopPreds;
for (BasicBlock::iterator I = Header->begin();
PHINode *PN = dyn_cast<PHINode>(I); ) {
++I;
if (Value *V = hasConstantValue(PN)) {
// This is a degenerate PHI already, don't modify it!
PN->replaceAllUsesWith(V);
Header->getInstList().erase(PN);
continue;
}
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) != PN ||
!L->contains(PN->getIncomingBlock(i)))
OuterLoopPreds.push_back(PN->getIncomingBlock(i));
// Scan this PHI node looking for a use of the PHI node by itself.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == PN &&
L->contains(PN->getIncomingBlock(i))) {
// Wow, we found something tasty to remove. Pull out all predecessors
// that have varying values in the loop. This handles the case when a
// PHI node has multiple instances of itself as arguments.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) != PN ||
!L->contains(PN->getIncomingBlock(i)))
OuterLoopPreds.push_back(PN->getIncomingBlock(i));
goto FoundExtraction;
}
}
return 0; // Nothing looks appetizing to separate out
FoundExtraction:
BasicBlock *NewBB = SplitBlockPredecessors(Header, ".outer", OuterLoopPreds);
// Update dominator information (set, immdom, domtree, and domfrontier)