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Revert r80926. It causes loop unswitch assertion and slow down some JIT tests significantly.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81101 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2009-09-06 02:26:10 +00:00
parent 92a97a9166
commit 8f78a58e14
11 changed files with 195 additions and 287 deletions
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92
lib/Transforms/Utils/BasicBlockUtils.cpp
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@ -24,7 +24,6 @@
#include "llvm/Analysis/Dominators.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ValueHandle.h"
#include <algorithm>
@ -320,8 +319,7 @@ BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
// The new block lives in whichever loop the old one did. This preserves
// LCSSA as well, because we force the split point to be after any PHI nodes.
// The new block lives in whichever loop the old one did.
if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
if (Loop *L = LI->getLoopFor(Old))
L->addBasicBlockToLoop(New, LI->getBase());
@ -355,12 +353,8 @@ BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
/// Preds array, which has NumPreds elements in it. The new block is given a
/// suffix of 'Suffix'.
///
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
/// In particular, it does not preserve LoopSimplify (because it's
/// complicated to handle the case where one of the edges being split
/// is an exit of a loop with other exits).
///
/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
/// DominanceFrontier, but no other analyses.
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
BasicBlock *const *Preds,
unsigned NumPreds, const char *Suffix,
@ -372,44 +366,19 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
// The new block unconditionally branches to the old block.
BranchInst *BI = BranchInst::Create(BB, NewBB);
LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
Loop *L = LI ? LI->getLoopFor(BB) : 0;
bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
// Move the edges from Preds to point to NewBB instead of BB.
// While here, if we need to preserve loop analyses, collect
// some information about how this split will affect loops.
bool HasLoopExit = false;
bool IsLoopEntry = !!L;
bool SplitMakesNewLoopHeader = false;
for (unsigned i = 0; i != NumPreds; ++i) {
for (unsigned i = 0; i != NumPreds; ++i)
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
if (LI) {
// If we need to preserve LCSSA, determine if any of
// the preds is a loop exit.
if (PreserveLCSSA)
if (Loop *PL = LI->getLoopFor(Preds[i]))
if (!PL->contains(BB))
HasLoopExit = true;
// If we need to preserve LoopInfo, note whether any of the
// preds crosses an interesting loop boundary.
if (L) {
if (L->contains(Preds[i]))
IsLoopEntry = false;
else
SplitMakesNewLoopHeader = true;
}
}
}
// Update dominator tree and dominator frontier if available.
DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
if (DT)
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
DF->splitBlock(NewBB);
AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
// Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
// node becomes an incoming value for BB's phi node. However, if the Preds
// list is empty, we need to insert dummy entries into the PHI nodes in BB to
@ -420,42 +389,20 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
return NewBB;
}
AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
if (L) {
if (IsLoopEntry) {
if (Loop *PredLoop = LI->getLoopFor(Preds[0])) {
// Add the new block to the nearest enclosing loop (and not an
// adjacent loop).
while (PredLoop && !PredLoop->contains(BB))
PredLoop = PredLoop->getParentLoop();
if (PredLoop)
PredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
}
} else {
L->addBasicBlockToLoop(NewBB, LI->getBase());
if (SplitMakesNewLoopHeader)
L->moveToHeader(NewBB);
}
}
// Otherwise, create a new PHI node in NewBB for each PHI node in BB.
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I++);
// Check to see if all of the values coming in are the same. If so, we
// don't need to create a new PHI node, unless it's needed for LCSSA.
Value *InVal = 0;
if (!HasLoopExit) {
InVal = PN->getIncomingValueForBlock(Preds[0]);
for (unsigned i = 1; i != NumPreds; ++i)
if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
InVal = 0;
break;
}
}
// don't need to create a new PHI node.
Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
for (unsigned i = 1; i != NumPreds; ++i)
if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
InVal = 0;
break;
}
if (InVal) {
// If all incoming values for the new PHI would be the same, just don't
// make a new PHI. Instead, just remove the incoming values from the old
@ -480,6 +427,13 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
// Add an incoming value to the PHI node in the loop for the preheader
// edge.
PN->addIncoming(InVal, NewBB);
// Check to see if we can eliminate this phi node.
if (Value *V = PN->hasConstantValue(DT)) {
PN->replaceAllUsesWith(V);
if (AA) AA->deleteValue(PN);
PN->eraseFromParent();
}
}
return NewBB;