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IRGen: simplify getSpareBitsForType #23442

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Mar 21, 2019
Merged

IRGen: simplify getSpareBitsForType #23442

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41 changes: 18 additions & 23 deletions lib/IRGen/GenType.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2182,32 +2182,27 @@ SpareBitVector IRGenModule::getSpareBitsForType(llvm::Type *scalarTy, Size size)
if (it != SpareBitsForTypes.end())
return it->second;

assert(DataLayout.getTypeAllocSizeInBits(scalarTy) <= size.getValueInBits() &&
assert(!isa<llvm::StructType>(scalarTy));

unsigned allocBits = size.getValueInBits();
assert(allocBits >= DataLayout.getTypeAllocSizeInBits(scalarTy) &&
"using a size that's smaller than LLVM's alloc size?");

{
// FIXME: Currently we only implement spare bits for primitive integer
// types.
assert(!isa<llvm::StructType>(scalarTy));

auto *intTy = dyn_cast<llvm::IntegerType>(scalarTy);
if (!intTy)
goto no_spare_bits;

// Round Integer-Of-Unusual-Size types up to their allocation size.
unsigned allocBits = size.getValueInBits();
assert(allocBits >= intTy->getBitWidth());
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I dropped this assertion since llvm::APInt::getBitsSetFrom already asserts this and the earlier DataLayout assertion will catch it first anyway probably.


// FIXME: Endianness.
SpareBitVector &result = SpareBitsForTypes[scalarTy];
result.appendClearBits(intTy->getBitWidth());
result.extendWithSetBits(allocBits);

// Allocate a new cache entry.
SpareBitVector &result = SpareBitsForTypes[scalarTy];

// FIXME: Currently we only implement spare bits for primitive integer
// types.
if (auto *intTy = dyn_cast<llvm::IntegerType>(scalarTy)) {
// Pad integers with spare bits up to their allocation size.
auto v = llvm::APInt::getBitsSetFrom(allocBits, intTy->getBitWidth());
// FIXME: byte swap v on big-endian platforms.
result = SpareBitVector::fromAPInt(v);
return result;
}

no_spare_bits:
SpareBitVector &result = SpareBitsForTypes[scalarTy];
result.appendClearBits(size.getValueInBits());

// No spare bits.
result = SpareBitVector::getConstant(allocBits, false);
return result;
}

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