rsmith added a comment. In D85191#2195923 <https://reviews.llvm.org/D85191#2195923>, @ebevhan wrote:
> In D85191#2193645 <https://reviews.llvm.org/D85191#2193645>, @rsmith wrote: > >>> This is not ideal, since it makes the calculations char size dependent, and >>> breaks for sizes that are not a multiple of the char size. >> >> How can we have a non-bitfield member whose size is not a multiple of the >> size of a char? > > Downstream, we have fixed-point types that are 24 bits large, but where the > char size is 16. The type then takes up 2 chars, where 8 of the bits are > padding. The only way in Clang to express that the width of the bit > representation of a type should be smaller than the number of chars it takes > up in memory -- and consequently, produce an `i24` in IR -- is to return a > non-charsize multiple from getTypeInfo. This violates the C and C++ language rules, which require the size of every type to be a multiple of the size of char. A type with 24 value bits and 8 padding bits should report a type size of 32 bits, just like `bool` reports a size of `CHAR_BIT` bits despite having only 1 value bit, and x86_64 `long double` reports a type size of 128 bits despite having only 80 value bits. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D85191/new/ https://reviews.llvm.org/D85191 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
