rustc_codegen_llvm: Feature Conversion Tidying
The author thinks we can improve `to_llvm_features`, a function to convert a Rust target feature name into an LLVM feature (or nothing, to ignore features unsupported by LLVM) for better maintainability.
1. We can simplify some clauses and some expressions.
2. There are some readability issues.
This PR attempts to resolve some of them by tidying many cases.
Prevent ABI changes affect EnzymeAD
This PR handles ABI changes for autodiff input arguments to improve Enzyme compatibility. Fundamentally this adjusts activities when a function argument is lowered as an `ScalarPair`, so there's no mismatch between diff activities and args. Also removes activities corresponding to ZSTs.
fixes: https://github.com/rust-lang/rust/issues/144025
r? `@ZuseZ4`
cg_llvm: Replace some DIBuilder wrappers with LLVM-C API bindings (part 4)
- Part of rust-lang/rust#134001
- Follow-up to rust-lang/rust#146631
---
This is another batch of LLVMDIBuilder binding migrations, replacing some our own LLVMRust bindings with bindings to upstream LLVM-C APIs.
Make llvm_enzyme a regular cargo feature
This makes it clearer that it is set by the build system rather than by the rustc that compiles the current rustc. It also avoids bootstrap needing to pass `--check-cfg llvm_enzyme` to rustc.
Remove unsized arg handling in `ArgAbiBuilderMethods::store_fn_arg` implementations
... since it is unreachable and would ICE anyway.
These branches are unreachable with how `store_fn_arg` is currently used (where it is called, unsized arguments are either: 1. not (yet) supported, or 2. handled differently)[^1], and even if they were reachable, they would ICE anyway, since they call [`OperandValue::store`](https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_codegen_ssa/mir/operand.rs.html#855-861), which calls [`OperandValue::store_with_flags`](https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_codegen_ssa/mir/operand.rs.html#887-926) which [panics on any unsized layout](https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_codegen_ssa/mir/operand.rs.html#900-903).
Also updates the `bug!` message in `store_arg` to not suggest `store_fn_arg` for unsized args.
[^1]: `store_fn_arg` is only nontrivially[^2] called in `compiler/rustc_codegen_ssa/src/mir/mod.rs` for: Line 428 `extern "rust-call"` tuple (un)splitting, which does not support unsized arguments, Line 496 which is only for sized `PassMode::Indirect` (`meta_attrs: None`) arguments, and Line 521 which is only for non-`PassMode::Indirect` arguments which can never be unsized.
[^2]: `<Bx as ArgAbiBuilderMethods>::store_fn_arg` is what is actually called, but codegen_llvm and codegen_gcc's builders both delegate to their own `codegen_crate::ArgAbiExt::store_fn_arg`, which contain the actual implementations that are changed in this PR.
This commit simplifies construction of `arch` from `sess.target.arch`.
It also preserves a reference to `sess.target.arch` as `raw_arch`
to make this function future proof.
cg_llvm: Replace some DIBuilder wrappers with LLVM-C API bindings (part 3)
- Part of rust-lang/rust#134001
- Follow-up to rust-lang/rust#136375
- Follow-up to rust-lang/rust#136632
---
This is another batch of LLVMDIBuilder binding migrations, replacing some our own LLVMRust bindings with bindings to upstream LLVM-C APIs.
This PR migrates all of the bindings that were touched by rust-lang/rust#136632, plus `LLVMDIBuilderCreateStructType`.
initial implementation of the darwin_objc unstable feature
Tracking issue: https://github.com/rust-lang/rust/issues/145496
This feature makes it possible to reference Objective-C classes and selectors using the same ABI used by native Objective-C on Apple/Darwin platforms. Without it, Rust code interacting with Objective-C must resort to loading classes and selectors using costly string-based lookups at runtime. With it, these references can be loaded efficiently at dynamic load time.
r? ```@tmandry```
try-job: `*apple*`
try-job: `x86_64-gnu-nopt`
This makes it clearer that it is set by the build system rather than by
the rustc that compiles the current rustc. It also avoids bootstrap
needing to pass --check-cfg llvm_enzyme to rustc.
Despite that the `fflags` register (representing floating point
exception flags) is stated as a flag register in the reference, it's not
in the default clobber list of the RISC-V inline assembly and it would
be better to fix it.
match clang's `va_arg` assembly on arm targets
tracking issue: https://github.com/rust-lang/rust/issues/44930
For this example
```rust
#![feature(c_variadic)]
#[unsafe(no_mangle)]
unsafe extern "C" fn variadic(a: f64, mut args: ...) -> f64 {
let b = args.arg::<f64>();
let c = args.arg::<f64>();
a + b + c
}
```
We currently generate (via llvm):
```asm
variadic:
sub sp, sp, #12
stmib sp, {r2, r3}
vmov d0, r0, r1
add r0, sp, #4
vldr d1, [sp, #4]
add r0, r0, #15
bic r0, r0, #7
vadd.f64 d0, d0, d1
add r1, r0, #8
str r1, [sp]
vldr d1, [r0]
vadd.f64 d0, d0, d1
vmov r0, r1, d0
add sp, sp, #12
bx lr
```
LLVM is not doing a good job. In fact, it's well-known that LLVM's implementation of `va_arg` is kind of bad, and we implement it ourselves (based on clang) for many targets already. For arm, our own `emit_ptr_va_arg` saves 3 instructions.
Next, it turns out it's important for LLVM to explicitly start and end the lifetime of the `va_list`. In https://github.com/rust-lang/rust/pull/146059 I already end the lifetime, but when looking at this again, I noticed that it is important to also start it, see https://godbolt.org/z/EGqvKTTsK: failing to explicitly start the lifetime uses an extra register.
So, the combination of `emit_ptr_va_arg` with starting/ending the lifetime makes rustc emit exactly the instructions that clang generates::
```asm
variadic:
sub sp, sp, #12
stmib sp, {r2, r3}
vmov d16, r0, r1
vldr d17, [sp, #4]
vadd.f64 d16, d16, d17
vldr d17, [sp, #12]
vadd.f64 d16, d16, d17
vmov r0, r1, d16
add sp, sp, #12
bx lr
```
The arguments to `emit_ptr_va_arg` are based on [the clang implementation](03dc2a41f3/clang/lib/CodeGen/Targets/ARM.cpp (L798-L844)).
r? ``@workingjubilee`` (I can re-roll if your queue is too full, but you do seem like the right person here)
try-job: armhf-gnu
Implement `#[rustc_align_static(N)]` on `static`s
Tracking issue: https://github.com/rust-lang/rust/issues/146177
```rust
#![feature(static_align)]
#[rustc_align_static(64)]
static SO_ALIGNED: u64 = 0;
```
We need a different attribute than `rustc_align` because unstable attributes are tied to their feature (we can't have two unstable features use the same unstable attribute). Otherwise this uses all of the same infrastructure as `#[rustc_align]`.
r? `@traviscross`
We need a different attribute than `rustc_align` because unstable attributes are
tied to their feature (we can't have two unstable features use the same
unstable attribute). Otherwise this uses all of the same infrastructure
as `#[rustc_align]`.
rename erase_regions to erase_and_anonymize_regions
I find it consistently confusing that `erase_regions` does more than replacing regions with `'erased`. it also makes some code look real goofy to be writing manual folders to erase regions with a comment saying "we cant use erase regions" :> or code that re-calls erase_regions on types with regions already erased just to anonymize all the bound regions.
r? lcnr
idk how i feel about the name being almost twice as long now
