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At end of LSR, replace uses of now constant (as result of SplitCriticalEdge) PHI node with the constant value.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43533 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-10-30 23:45:15 +00:00
parent 20b7907c1c
commit 0e0014d049
1 changed files with 33 additions and 9 deletions
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42
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -228,6 +228,21 @@ DeleteTriviallyDeadInstructions(SmallPtrSet<Instruction*,16> &Insts) {
while (!Insts.empty()) {
Instruction *I = *Insts.begin();
Insts.erase(I);
if (PHINode *PN = dyn_cast<PHINode>(I)) {
// If all incoming values to the Phi are the same, we can replace the Phi
// with that value.
if (Value *PNV = PN->hasConstantValue()) {
if (Instruction *U = dyn_cast<Instruction>(PNV))
Insts.insert(U);
PN->replaceAllUsesWith(PNV);
SE->deleteValueFromRecords(PN);
PN->eraseFromParent();
Changed = true;
continue;
}
}
if (isInstructionTriviallyDead(I)) {
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
@ -359,7 +374,8 @@ static bool getSCEVStartAndStride(const SCEVHandle &SH, Loop *L,
/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
/// should use the post-inc value).
static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
Loop *L, DominatorTree *DT, Pass *P) {
Loop *L, DominatorTree *DT, Pass *P,
SmallPtrSet<Instruction*,16> &DeadInsts){
// If the user is in the loop, use the preinc value.
if (L->contains(User->getParent())) return false;
@ -399,6 +415,9 @@ static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
e = PN->getNumIncomingValues();
if (--NumUses == 0) break;
}
// PHI node might have become a constant value after SplitCriticalEdge.
DeadInsts.insert(User);
return true;
}
@ -461,7 +480,7 @@ bool LoopStrengthReduce::AddUsersIfInteresting(Instruction *I, Loop *L,
// Okay, we found a user that we cannot reduce. Analyze the instruction
// and decide what to do with it. If we are a use inside of the loop, use
// the value before incrementation, otherwise use it after incrementation.
if (IVUseShouldUsePostIncValue(User, I, L, DT, this)) {
if (IVUseShouldUsePostIncValue(User, I, L, DT, this, DeadInsts)) {
// The value used will be incremented by the stride more than we are
// expecting, so subtract this off.
SCEVHandle NewStart = SE->getMinusSCEV(Start, Stride);
@ -522,8 +541,8 @@ namespace {
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
// to it.
void RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
SCEVExpander &Rewriter, Loop *L,
Pass *P);
SCEVExpander &Rewriter, Loop *L, Pass *P,
SmallPtrSet<Instruction*,16> &DeadInsts);
Value *InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
SCEVExpander &Rewriter,
@ -584,8 +603,8 @@ Value *BasedUser::InsertCodeForBaseAtPosition(const SCEVHandle &NewBase,
// operands of Inst to use the new expression 'NewBase', with 'Imm' added
// to it.
void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
SCEVExpander &Rewriter,
Loop *L, Pass *P) {
SCEVExpander &Rewriter, Loop *L, Pass *P,
SmallPtrSet<Instruction*,16> &DeadInsts) {
if (!isa<PHINode>(Inst)) {
// By default, insert code at the user instruction.
BasicBlock::iterator InsertPt = Inst;
@ -676,6 +695,10 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEVHandle &NewBase,
Rewriter.clear();
}
}
// PHI node might have become a constant value after SplitCriticalEdge.
DeadInsts.insert(Inst);
DOUT << " CHANGED: IMM =" << *Imm << " Inst = " << *Inst;
}
@ -1373,7 +1396,8 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
// Add BaseV to the PHI value if needed.
RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
User.RewriteInstructionToUseNewBase(RewriteExpr, Rewriter, L, this);
User.RewriteInstructionToUseNewBase(RewriteExpr, Rewriter, L, this,
DeadInsts);
// Mark old value we replaced as possibly dead, so that it is elminated
// if we just replaced the last use of that value.
@ -1457,7 +1481,7 @@ namespace {
/// v1 = v1 + 3
/// if (v1 < 30) goto loop
ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
IVStrideUse* &CondUse,
IVStrideUse* &CondUse,
const SCEVHandle* &CondStride) {
if (StrideOrder.size() < 2 ||
IVUsesByStride[*CondStride].Users.size() != 1)
@ -1734,7 +1758,7 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
PHINode *PN;
while ((PN = dyn_cast<PHINode>(I))) {
++I; // Preincrement iterator to avoid invalidating it when deleting PN.
// At this point, we know that we have killed one or more GEP
// instructions. It is worth checking to see if the cann indvar is also
// dead, so that we can remove it as well. The requirements for the cann