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Allow scalarrepl to treat an all-zero GEP just as bitcast.

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This includes not marking a GEP involving a vector as unsafe, but only when it
has all zero indices. This allows scalarrepl to work in a few more cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57177 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthijs Kooijman
2008-10-06 16:23:31 +00:00
parent 96f945267c
commit 5fac55fafb
2 changed files with 52 additions and 14 deletions
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42
lib/Transforms/Scalar/ScalarReplAggregates.cpp
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@@ -530,7 +530,8 @@ void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
return MarkUnsafe(Info);
}
}
bool hasVector = false;
// Walk through the GEP type indices, checking the types that this indexes
// into.
@@ -539,22 +540,30 @@ void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
if (isa<StructType>(*I))
continue;
// Don't SROA pointers into vectors.
if (isa<VectorType>(*I))
return MarkUnsafe(Info);
// Otherwise, we must have an index into an array type. Verify that this is
// an in-range constant integer. Specifically, consider A[0][i]. We
// cannot know that the user isn't doing invalid things like allowing i to
// index an out-of-range subscript that accesses A[1]. Because of this, we
// have to reject SROA of any accesses into structs where any of the
// components are variables.
ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
if (!IdxVal) return MarkUnsafe(Info);
if (IdxVal->getZExtValue() >= cast<ArrayType>(*I)->getNumElements())
return MarkUnsafe(Info);
// Are all indices still zero?
IsAllZeroIndices &= IdxVal->isZero();
if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
// This GEP indexes an array. Verify that this is an in-range constant
// integer. Specifically, consider A[0][i]. We cannot know that the user
// isn't doing invalid things like allowing i to index an out-of-range
// subscript that accesses A[1]. Because of this, we have to reject SROA
// of any accesses into structs where any of the components are variables.
if (IdxVal->getZExtValue() >= AT->getNumElements())
return MarkUnsafe(Info);
}
// Note if we've seen a vector type yet
hasVector |= isa<VectorType>(*I);
// Don't SROA pointers into vectors, unless all indices are zero. When all
// indices are zero, we only consider this GEP as a bitcast, but will still
// not consider breaking up the vector.
if (hasVector && !IsAllZeroIndices)
return MarkUnsafe(Info);
}
// If there are any non-simple uses of this getelementptr, make sure to reject
@@ -661,6 +670,11 @@ void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
// It is likely that OtherPtr is a bitcast, if so, remove it.
if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
OtherPtr = BC->getOperand(0);
// All zero GEPs are effectively casts
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
if (GEP->hasAllZeroIndices())
OtherPtr = GEP->getOperand(0);
if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
if (BCE->getOpcode() == Instruction::BitCast)
OtherPtr = BCE->getOperand(0);