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Only reuse a previous IV if it would not require a type conversion.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29186 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2006-07-18 19:07:58 +00:00
parent 0a01212857
commit 31e773147b
1 changed files with 20 additions and 17 deletions
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37
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -187,7 +187,7 @@ private:
void OptimizeIndvars(Loop *L);
unsigned CheckForIVReuse(const SCEVHandle &Stride, IVExpr &IV);
unsigned CheckForIVReuse(const SCEVHandle&, IVExpr&, const Type*);
void StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IVUsersOfOneStride &Uses,
@ -872,7 +872,7 @@ static bool isZero(SCEVHandle &V) {
/// mode scale component. This allows the users of this stride to be rewritten
/// as prev iv * factor. It returns 0 if no reuse is possible.
unsigned LoopStrengthReduce::CheckForIVReuse(const SCEVHandle &Stride,
IVExpr &IV) {
IVExpr &IV, const Type *Ty) {
if (!TLI) return 0;
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
@ -892,7 +892,9 @@ unsigned LoopStrengthReduce::CheckForIVReuse(const SCEVHandle &Stride,
for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
IE = SI->second.IVs.end(); II != IE; ++II)
// FIXME: Only handle base == 0 for now.
if (isZero(II->Base)) {
// Only reuse previous IV if it would not require a type conversion.
if (isZero(II->Base) &&
II->Base->getType()->isLosslesslyConvertibleTo(Ty)) {
IV = *II;
return Scale;
}
@ -929,20 +931,6 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
"Base value is not loop invariant!");
}
// Check if it is possible to reuse a IV with stride that is factor of this
// stride. And the multiple is a number that can be encoded in the scale
// field of the target addressing mode.
PHINode *NewPHI = NULL;
Value *IncV = NULL;
IVExpr ReuseIV;
unsigned RewriteFactor = CheckForIVReuse(Stride, ReuseIV);
if (RewriteFactor != 0) {
DEBUG(std::cerr << "BASED ON IV of STRIDE " << *ReuseIV.Stride
<< " and BASE " << *ReuseIV.Base << " :\n");
NewPHI = ReuseIV.PHI;
IncV = ReuseIV.IncV;
}
// We now have a whole bunch of uses of like-strided induction variables, but
// they might all have different bases. We want to emit one PHI node for this
// stride which we fold as many common expressions (between the IVs) into as
@ -953,6 +941,21 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
SCEVHandle CommonExprs =
RemoveCommonExpressionsFromUseBases(UsersToProcess);
// Check if it is possible to reuse a IV with stride that is factor of this
// stride. And the multiple is a number that can be encoded in the scale
// field of the target addressing mode.
PHINode *NewPHI = NULL;
Value *IncV = NULL;
IVExpr ReuseIV;
unsigned RewriteFactor = CheckForIVReuse(Stride, ReuseIV,
CommonExprs->getType());
if (RewriteFactor != 0) {
DEBUG(std::cerr << "BASED ON IV of STRIDE " << *ReuseIV.Stride
<< " and BASE " << *ReuseIV.Base << " :\n");
NewPHI = ReuseIV.PHI;
IncV = ReuseIV.IncV;
}
// Next, figure out what we can represent in the immediate fields of
// 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