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Rollup merge of #142854 - folkertdev:centralize-min-function-alignment, r=workingjubilee

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centralize `-Zmin-function-alignment` logic

tracking issue: https://github.com/rust-lang/rust/issues/82232
discussed in: https://github.com/rust-lang/rust/pull/142824#discussion_r2160056244

Apply the `-Zmin-function-alignment` value to the alignment field of the function attributes when those are created, so that individual backends don't need to consider it.

The one exception right now is cranelift, because it can't yet set the alignment for individual functions, but it can (and does) set the global minimum function alignment.

cc ``@RalfJung`` I think this is an improvement regardless, is there anything else that should be done for miri?
This commit is contained in:
Matthias Krüger
2025-06-23 06:07:20 +02:00
committed by GitHub
parent 2357fb05bb a123a36a1f
commit 57abad8cc5
4 changed files with 10 additions and 17 deletions
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6
compiler/rustc_codegen_ssa/src/codegen_attrs.rs
View File

@@ -145,6 +145,12 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
}
}
// Apply the minimum function alignment here, so that individual backends don't have to.
codegen_fn_attrs.alignment = Ord::max(
codegen_fn_attrs.alignment,
tcx.sess.opts.unstable_opts.min_function_alignment,
);
let Some(Ident { name, .. }) = attr.ident() else {
continue;
};

8
compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
View File

@@ -131,12 +131,8 @@ fn prefix_and_suffix<'tcx>(
let attrs = tcx.codegen_fn_attrs(instance.def_id());
let link_section = attrs.link_section.map(|symbol| symbol.as_str().to_string());
// function alignment can be set globally with the `-Zmin-function-alignment=<n>` flag;
// the alignment from a `#[repr(align(<n>))]` is used if it specifies a higher alignment.
// if no alignment is specified, an alignment of 4 bytes is used.
let min_function_alignment = tcx.sess.opts.unstable_opts.min_function_alignment;
let align_bytes =
Ord::max(min_function_alignment, attrs.alignment).map(|a| a.bytes()).unwrap_or(4);
// If no alignment is specified, an alignment of 4 bytes is used.
let align_bytes = attrs.alignment.map(|a| a.bytes()).unwrap_or(4);
// In particular, `.arm` can also be written `.code 32` and `.thumb` as `.code 16`.
let (arch_prefix, arch_suffix) = if is_arm {