Several codegen tests are currently failing due to making
assumptions that are not valid for the s390x architecture:
- catch-unwind.rs: fails due to inlining differences.
Already ignored on another platform for the same reason.
Solution: Ignore on s390x.
- remap_path_prefix/main.rs: fails due to different alignment
requirement for string constants.
Solution: Do not test for the alignment requirement.
- repr-transparent-aggregates-1.rs: many ABI assumptions.
Already ignored on many platforms for the same reason.
Solution: Ignore on s390x.
- repr-transparent.rs: no vector ABI by default on s390x.
Already ignored on another platform for a similar reason.
Solution: Ignore on s390x.
- uninit-consts.rs: hard-coded little-endian constant.
Solution: Match both little- and big-endian versions.
Fixes part of https://github.com/rust-lang/rust/issues/105383.
Beyond `&`/`&mut`/`Box`, this covers `char`, discriminants, `NonZero*`, etc.
All such types currently cause a Miri error if left uninitialized,
and an `invalid_value` lint in cases like `mem::uninitialized::<char>()`
Note that this _does not_ change whether or not it is UB for `u64` (or
other integer types with no invalid values) to be undef.
This should have no real effect in most cases, as e.g. `hidden`
visibility already implies `dso_local` (or at least LLVM IR does not
preserve the `dso_local` setting if the item is already `hidden`), but
it should fix `-Crelocation-model=static` and improve codegen in
executables.
Note that this PR does not exhaustively port the logic in [clang]. Only
the obviously correct portion and what is necessary to fix a regression
from LLVM 12 that relates to `-Crelocation_model=static`.
Fixes#83335
[clang]: 3001d080c8/clang/lib/CodeGen/CodeGenModule.cpp (L945-L1039)
The x86_64 SysV ABI should use exact sizes for small structs passed in
registers, i.e. a struct that occupies 3 bytes should use an i24,
instead of the i32 it currently uses.
Refs #45543
