If we know that x is nonzero and not a power of 2, then
llvm::findLastSet(x) + 1 is the index of the bit just above the
highest set bit in x. That is, 1 << (llvm::findLastSet(x) + 1) is the
same as llvm::bit_ceil(x).
Since llvm::bit_ceil is a nop on a power of 2, we can unconditionally
call llvm::bit_ceil. The end result actually matches the comment.
// For Swift's purposes, this is always just the store size of the type
// rounded up to a power of 2.
auto size = (unsigned long long) getTypeStoreSize(CGM, type).getQuantity();
- if (!isPowerOf2(size)) {
- size = 1ULL << (llvm::findLastSet(size, llvm::ZB_Undefined) + 1);
- }
+ size = llvm::bit_ceil(size);
assert(CGM.getDataLayout().getABITypeAlign(type) <= size);
return CharUnits::fromQuantity(size);
}