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.
rustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc dev guide.