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[SCEV] Construct GEP expression more efficiently (NFCI) 

Instead of performing a sequence of pairwise additions, directly
construct a multi-operand add expression.

This should be NFC modulo any SCEV canonicalization deficiencies.
This commit is contained in:
Nikita Popov 2020-11-01 18:34:01 +01:00
parent ca38652b9a
commit 6ec56467cb
1 changed files with 5 additions and 9 deletions
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14
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -3421,9 +3421,9 @@ ScalarEvolution::getGEPExpr(GEPOperator *GEP,
SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW
: SCEV::FlagAnyWrap;
const SCEV *TotalOffset = getZero(IntIdxTy);
Type *CurTy = GEP->getType();
bool FirstIter = true;
SmallVector<const SCEV *, 4> AddOps{BaseExpr};
for (const SCEV *IndexExpr : IndexExprs) {
// Compute the (potentially symbolic) offset in bytes for this index.
if (StructType *STy = dyn_cast<StructType>(CurTy)) {
@ -3431,9 +3431,7 @@ ScalarEvolution::getGEPExpr(GEPOperator *GEP,
ConstantInt *Index = cast<SCEVConstant>(IndexExpr)->getValue();
unsigned FieldNo = Index->getZExtValue();
const SCEV *FieldOffset = getOffsetOfExpr(IntIdxTy, STy, FieldNo);
// Add the field offset to the running total offset.
TotalOffset = getAddExpr(TotalOffset, FieldOffset);
AddOps.push_back(FieldOffset);
// Update CurTy to the type of the field at Index.
CurTy = STy->getTypeAtIndex(Index);
@ -3454,14 +3452,12 @@ ScalarEvolution::getGEPExpr(GEPOperator *GEP,
// Multiply the index by the element size to compute the element offset.
const SCEV *LocalOffset = getMulExpr(IndexExpr, ElementSize, Wrap);
// Add the element offset to the running total offset.
TotalOffset = getAddExpr(TotalOffset, LocalOffset);
AddOps.push_back(LocalOffset);
}
}
// Add the total offset from all the GEP indices to the base.
return getAddExpr(BaseExpr, TotalOffset, Wrap);
// Add the base and all the offsets together.
return getAddExpr(AddOps, Wrap);
}
std::tuple<SCEV *, FoldingSetNodeID, void *>