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[ConstantFolding] Use FoldBitCast correctly

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Previously we might attempt to use a BitCast to turn bits into vectors of pointers,
but that requires an inttoptr cast to be legal. Add an assertion to detect the formation of illegal bitcast attempts
early (in the tests, we often constant-fold away the result before getting to this assertion check),
while being careful to still handle the early-return conditions without adding extra complexity in the result.

Patch by Jameson Nash <jameson@juliacomputing.com>.

Differential Revision: https://reviews.llvm.org/D65057

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372940 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Keno Fischer
2019-09-26 02:07:51 +00:00
parent 206c4da0c1
commit f005ce18dd
1 changed files with 20 additions and 2 deletions
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lib/Analysis/ConstantFolding.cpp
+20 -2
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@@ -93,6 +93,9 @@ static Constant *foldConstVectorToAPInt(APInt &Result, Type *DestTy,
/// This always returns a non-null constant, but it may be a
/// ConstantExpr if unfoldable.
Constant *FoldBitCast(Constant *C, Type *DestTy, const DataLayout &DL) {
assert(CastInst::castIsValid(Instruction::BitCast, C, DestTy) &&
"Invalid constantexpr bitcast!");
// Catch the obvious splat cases.
if (C->isNullValue() && !DestTy->isX86_MMXTy())
return Constant::getNullValue(DestTy);
@@ -521,8 +524,23 @@ Constant *FoldReinterpretLoadFromConstPtr(Constant *C, Type *LoadTy,
return nullptr;
C = FoldBitCast(C, MapTy->getPointerTo(AS), DL);
if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, MapTy, DL))
return FoldBitCast(Res, LoadTy, DL);
if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, MapTy, DL)) {
if (Res->isNullValue() && !LoadTy->isX86_MMXTy())
// Materializing a zero can be done trivially without a bitcast
return Constant::getNullValue(LoadTy);
Type *CastTy = LoadTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(LoadTy) : LoadTy;
Res = FoldBitCast(Res, CastTy, DL);
if (LoadTy->isPtrOrPtrVectorTy()) {
// For vector of pointer, we needed to first convert to a vector of integer, then do vector inttoptr
if (Res->isNullValue() && !LoadTy->isX86_MMXTy())
return Constant::getNullValue(LoadTy);
if (DL.isNonIntegralPointerType(LoadTy->getScalarType()))
// Be careful not to replace a load of an addrspace value with an inttoptr here
return nullptr;
Res = ConstantExpr::getCast(Instruction::IntToPtr, Res, LoadTy);
}
return Res;
}
return nullptr;
}