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Generalize the cast-of-addrec folding to handle folding of SCEVs like

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(sext i8 {-128,+,1} to i64) to i64 {-128,+,1}, where the iteration
crosses from negative to positive, but is still safe if the trip
count is within range.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70421 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-04-29 22:28:28 +00:00
parent f159ccd1cd
commit ac70ceafbc
3 changed files with 164 additions and 46 deletions
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79
lib/Analysis/ScalarEvolution.cpp
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@ -718,7 +718,7 @@ SCEVHandle ScalarEvolution::getZeroExtendExpr(const SCEVHandle &Op,
SCEVHandle BECount = getBackedgeTakenCount(AR->getLoop());
if (!isa<SCEVCouldNotCompute>(BECount)) {
// Manually compute the final value for AR, checking for
// overflow at each step.
// overflow.
SCEVHandle Start = AR->getStart();
SCEVHandle Step = AR->getStepRecurrence(*this);
@ -730,41 +730,34 @@ SCEVHandle ScalarEvolution::getZeroExtendExpr(const SCEVHandle &Op,
getTruncateOrZeroExtend(CastedBECount, BECount->getType())) {
const Type *WideTy =
IntegerType::get(getTypeSizeInBits(Start->getType()) * 2);
// Check whether Start+Step*BECount has no unsigned overflow.
SCEVHandle ZMul =
getMulExpr(CastedBECount,
getTruncateOrZeroExtend(Step, Start->getType()));
// Check whether Start+Step*BECount has no unsigned overflow.
if (getZeroExtendExpr(ZMul, WideTy) ==
getMulExpr(getZeroExtendExpr(CastedBECount, WideTy),
getZeroExtendExpr(Step, WideTy))) {
SCEVHandle Add = getAddExpr(Start, ZMul);
if (getZeroExtendExpr(Add, WideTy) ==
getAddExpr(getZeroExtendExpr(Start, WideTy),
getZeroExtendExpr(ZMul, WideTy)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getZeroExtendExpr(Step, Ty),
AR->getLoop());
}
SCEVHandle Add = getAddExpr(Start, ZMul);
if (getZeroExtendExpr(Add, WideTy) ==
getAddExpr(getZeroExtendExpr(Start, WideTy),
getMulExpr(getZeroExtendExpr(CastedBECount, WideTy),
getZeroExtendExpr(Step, WideTy))))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getZeroExtendExpr(Step, Ty),
AR->getLoop());
// Similar to above, only this time treat the step value as signed.
// This covers loops that count down.
SCEVHandle SMul =
getMulExpr(CastedBECount,
getTruncateOrSignExtend(Step, Start->getType()));
// Check whether Start+Step*BECount has no unsigned overflow.
if (getSignExtendExpr(SMul, WideTy) ==
getMulExpr(getZeroExtendExpr(CastedBECount, WideTy),
getSignExtendExpr(Step, WideTy))) {
SCEVHandle Add = getAddExpr(Start, SMul);
if (getZeroExtendExpr(Add, WideTy) ==
getAddExpr(getZeroExtendExpr(Start, WideTy),
getSignExtendExpr(SMul, WideTy)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
AR->getLoop());
}
Add = getAddExpr(Start, SMul);
if (getZeroExtendExpr(Add, WideTy) ==
getAddExpr(getZeroExtendExpr(Start, WideTy),
getMulExpr(getZeroExtendExpr(CastedBECount, WideTy),
getSignExtendExpr(Step, WideTy))))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getZeroExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
AR->getLoop());
}
}
}
@ -807,37 +800,31 @@ SCEVHandle ScalarEvolution::getSignExtendExpr(const SCEVHandle &Op,
SCEVHandle BECount = getBackedgeTakenCount(AR->getLoop());
if (!isa<SCEVCouldNotCompute>(BECount)) {
// Manually compute the final value for AR, checking for
// overflow at each step.
// overflow.
SCEVHandle Start = AR->getStart();
SCEVHandle Step = AR->getStepRecurrence(*this);
// Check whether the backedge-taken count can be losslessly casted to
// the addrec's type. The count needs to be the same whether sign
// extended or zero extended.
// the addrec's type. The count is always unsigned.
SCEVHandle CastedBECount =
getTruncateOrZeroExtend(BECount, Start->getType());
if (BECount ==
getTruncateOrZeroExtend(CastedBECount, BECount->getType()) &&
BECount ==
getTruncateOrSignExtend(CastedBECount, BECount->getType())) {
getTruncateOrZeroExtend(CastedBECount, BECount->getType())) {
const Type *WideTy =
IntegerType::get(getTypeSizeInBits(Start->getType()) * 2);
// Check whether Start+Step*BECount has no signed overflow.
SCEVHandle SMul =
getMulExpr(CastedBECount,
getTruncateOrSignExtend(Step, Start->getType()));
// Check whether Start+Step*BECount has no signed overflow.
if (getSignExtendExpr(SMul, WideTy) ==
getMulExpr(getSignExtendExpr(CastedBECount, WideTy),
getSignExtendExpr(Step, WideTy))) {
SCEVHandle Add = getAddExpr(Start, SMul);
if (getSignExtendExpr(Add, WideTy) ==
getAddExpr(getSignExtendExpr(Start, WideTy),
getSignExtendExpr(SMul, WideTy)))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
AR->getLoop());
}
SCEVHandle Add = getAddExpr(Start, SMul);
if (getSignExtendExpr(Add, WideTy) ==
getAddExpr(getSignExtendExpr(Start, WideTy),
getMulExpr(getZeroExtendExpr(CastedBECount, WideTy),
getSignExtendExpr(Step, WideTy))))
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
AR->getLoop());
}
}
}