009280c5e3
When passing a 16 (or higher) aligned struct by value on ppc64le, it needs to be passed as an array of `i128` rather than an array of `i64`. This will force the use of an even starting register. For the case of a 16 byte struct with alignment 16 it is important that `[1 x i128]` is used instead of `i128` -- apparently, the latter will get treated similarly to `[2 x i64]`, not exhibiting the correct ABI. Add a `force_array` flag to `Uniform` to support this. The relevant clang code can be found here:fe2119a7b0/clang/lib/CodeGen/Targets/PPC.cpp (L878-L884)fe2119a7b0/clang/lib/CodeGen/Targets/PPC.cpp (L780-L784)I think the corresponding psABI wording is this: > Fixed size aggregates and unions passed by value are mapped to as > many doublewords of the parameter save area as the value uses in > memory. Aggregrates and unions are aligned according to their > alignment requirements. This may result in doublewords being > skipped for alignment. In particular the last sentence. Fixes https://github.com/rust-lang/rust/issues/122767.
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.