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Fix PR404: Loop simplify is really slow on 252.eon

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This eliminates an N*N*logN algorithm from the loop simplify pass, replacing
it with a much simpler and faster alternative.  In a debug build, this reduces
gccas time on eon from 85s to 42s.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@14851 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-07-15 04:27:04 +00:00
parent 9e229b2802
commit 507e3d6dc3
1 changed files with 12 additions and 12 deletions
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24
lib/Transforms/Utils/LoopSimplify.cpp
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@ -147,6 +147,9 @@ bool LoopSimplify::ProcessLoop(Loop *L) {
Changed = true;
}
DominatorSet &DS = getAnalysis<DominatorSet>(); // Update dominator info
// Next, check to make sure that all exit nodes of the loop only have
// predecessors that are inside of the loop. This check guarantees that the
// loop preheader/header will dominate the exit blocks. If the exit block has
@ -155,19 +158,16 @@ bool LoopSimplify::ProcessLoop(Loop *L) {
L->getExitBlocks(ExitBlocks);
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock);
PI != PE; ++PI)
if (!L->contains(*PI)) {
BasicBlock *NewBB = RewriteLoopExitBlock(L, ExitBlock);
for (unsigned j = i; j != ExitBlocks.size(); ++j)
if (ExitBlocks[j] == ExitBlock)
ExitBlocks[j] = NewBB;
NumInserted++;
Changed = true;
break;
}
if (!DS.dominates(L->getHeader(), ExitBlock)) {
BasicBlock *NewBB = RewriteLoopExitBlock(L, ExitBlock);
for (unsigned j = i; j != ExitBlocks.size(); ++j)
if (ExitBlocks[j] == ExitBlock)
ExitBlocks[j] = NewBB;
NumInserted++;
Changed = true;
}
}
// If the header has more than two predecessors at this point (from the
// preheader and from multiple backedges), we must adjust the loop.