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Preserve canonical loop form.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35829 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2007-04-09 20:19:46 +00:00
parent 44f5fb46b0
commit 5464b96073
1 changed files with 55 additions and 5 deletions
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60
lib/Transforms/Scalar/LoopRotation.cpp
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@ -75,6 +75,11 @@ namespace {
/// not available.
const RenameData *findReplacementData(Instruction *I);
/// After loop rotation, loop pre-header has multiple sucessors.
/// Insert one forwarding basic block to ensure that loop pre-header
/// has only one successor.
void preserveCanonicalLoopForm(LPPassManager &LPM);
private:
Loop *L;
@ -121,11 +126,8 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
if (L->getBlocks().size() == 1)
return false;
if (!OrigHeader || !OrigLatch || !OrigPreHeader)
return false;
if (!OrigHeader || !OrigLatch || !OrigPreHeader)
return false;
assert (OrigHeader && OrigLatch && OrigPreHeader &&
"Loop is not in cannocial form");
// If loop header is not one of the loop exit block then
// either this loop is already rotated or it is not
@ -344,6 +346,8 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
// Make NewHeader as the new header for the loop.
L->moveToHeader(NewHeader);
preserveCanonicalLoopForm(LPM);
NumRotated++;
return true;
}
@ -415,3 +419,49 @@ const RenameData *LoopRotate::findReplacementData(Instruction *In) {
}
return NULL;
}
/// After loop rotation, loop pre-header has multiple sucessors.
/// Insert one forwarding basic block to ensure that loop pre-header
/// has only one successor.
void LoopRotate::preserveCanonicalLoopForm(LPPassManager &LPM) {
// Right now original pre-header has two successors, new header and
// exit block. Insert new block between original pre-header and
// new header such that loop's new pre-header has only one successor.
BasicBlock *NewPreHeader = new BasicBlock("bb.nph", OrigHeader->getParent(),
OrigPreHeader);
LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
if (Loop *PL = LI.getLoopFor(OrigPreHeader))
PL->addBasicBlockToLoop(NewPreHeader, LI);
new BranchInst(NewHeader, NewPreHeader);
BranchInst *OrigPH_BI = cast<BranchInst>(OrigPreHeader->getTerminator());
if (OrigPH_BI->getSuccessor(0) == NewHeader)
OrigPH_BI->setSuccessor(0, NewPreHeader);
else {
assert (OrigPH_BI->getSuccessor(1) == NewPreHeader &&
"Unexpected original pre-header terminator");
OrigPH_BI->setSuccessor(1, NewPreHeader);
}
for (BasicBlock::iterator I = NewHeader->begin(), E = NewHeader->end();
I != E; ++I) {
Instruction *In = I;
PHINode *PN = dyn_cast<PHINode>(In);
if (!PN)
break;
int index = PN->getBasicBlockIndex(OrigPreHeader);
assert (index != -1 && "Expected incoming value from Original PreHeader");
PN->setIncomingBlock(index, NewPreHeader);
assert (PN->getBasicBlockIndex(OrigPreHeader) == -1 &&
"Expected only one incoming value from Original PreHeader");
}
assert (NewHeader && L->getHeader() == NewHeader
&& "Invalid loop header after loop rotation");
assert (NewPreHeader && L->getLoopPreheader() == NewPreHeader
&& "Invalid loop preheader after loop rotation");
assert (L->getLoopLatch()
&& "Invalid loop latch after loop rotation");
}