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Clean up previous patch: PHI uses should not prevent iv reuse if all other uses are addresses. This trades a constant multiply for one fewer iv. 

llvm-svn: 45251
This commit is contained in:
Evan Cheng 2007-12-20 02:20:53 +00:00
parent 16a51da0e2
commit 26ee54eb05
1 changed files with 16 additions and 35 deletions
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51
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -997,8 +997,11 @@ bool LoopStrengthReduce::ValidStride(bool HasBaseReg,
AccessTy = SI->getOperand(0)->getType();
else if (LoadInst *LI = dyn_cast<LoadInst>(UsersToProcess[i].Inst))
AccessTy = LI->getType();
else if (PHINode *PN = dyn_cast<PHINode>(UsersToProcess[i].Inst))
AccessTy = PN->getType();
else if (isa<PHINode>(UsersToProcess[i].Inst)) {
if (AllowPHIIVReuse)
continue;
return false;
}
TargetLowering::AddrMode AM;
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
@ -1126,34 +1129,6 @@ static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
return isAddress;
}
/// isAddressUsePHI - Returns if all uses of the specified PHI node are using
/// the PHI node value as an address.
static void isAddressUsePHI(Instruction *Inst,
SmallPtrSet<Instruction*,16> &Processed,
bool &Result) {
if (!Result || !Processed.insert(Inst))
return;
for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
if (isa<PHINode>(User) && !Processed.count(User)) {
bool ThisResult = true;
isAddressUsePHI(User, Processed, ThisResult);
if (!ThisResult) {
Result = false;
return;
}
continue;
}
if (!isAddressUse(User, cast<Value>(Inst))) {
Result = false;
return;
}
}
}
// CollectIVUsers - Transform our list of users and offsets to a bit more
// complex table. In this new vector, each 'BasedUser' contains 'Base' the base
// of the strided accessas well as the old information from Uses. We
@ -1191,6 +1166,7 @@ SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
// instructions. If we can represent anything there, move it to the imm
// fields of the BasedUsers. We do this so that it increases the commonality
// of the remaining uses.
unsigned NumPHI = 0;
for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
// If the user is not in the current loop, this means it is using the exit
// value of the IV. Do not put anything in the base, make sure it's all in
@ -1204,17 +1180,16 @@ SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
// Addressing modes can be folded into loads and stores. Be careful that
// the store is through the expression, not of the expression though.
bool isPtrPHI = false;
bool isPHI = false;
bool isAddress = isAddressUse(UsersToProcess[i].Inst,
UsersToProcess[i].OperandValToReplace);
if (isa<PHINode>(UsersToProcess[i].Inst)) {
SmallPtrSet<Instruction*,16> Processed;
isPtrPHI = true;
isAddressUsePHI(UsersToProcess[i].Inst, Processed, isPtrPHI);
isPHI = true;
++NumPHI;
}
// If this use isn't an address, then not all uses are addresses.
if (!isAddress && !(AllowPHIIVReuse && isPtrPHI))
if (!isAddress && !(AllowPHIIVReuse && isPHI))
AllUsesAreAddresses = false;
MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
@ -1222,6 +1197,12 @@ SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride,
}
}
// If one of the use if a PHI node and all other uses are addresses, still
// allow iv reuse. Essentially we are trading one constant multiplication
// for one fewer iv.
if (NumPHI > 1)
AllUsesAreAddresses = false;
return CommonExprs;
}