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centralize -Zmin-function-alignment logic

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This commit is contained in:
Folkert de Vries 2025-06-22 00:47:10 +02:00
parent 6d0c9e2a1c
commit a123a36a1f
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GPG key ID: 1F17F6FFD112B97C
4 changed files with 10 additions and 17 deletions
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6
compiler/rustc_codegen_llvm/src/attributes.rs
View file

@ -491,11 +491,7 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
let allocated_pointer = AttributeKind::AllocatedPointer.create_attr(cx.llcx);
attributes::apply_to_llfn(llfn, AttributePlace::Argument(0), &[allocated_pointer]);
}
// 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 let Some(align) =
Ord::max(cx.tcx.sess.opts.unstable_opts.min_function_alignment, codegen_fn_attrs.alignment)
{
if let Some(align) = codegen_fn_attrs.alignment {
llvm::set_alignment(llfn, align);
}
if let Some(backchain) = backchain_attr(cx) {

6
compiler/rustc_codegen_ssa/src/codegen_attrs.rs
View file

@ -126,6 +126,12 @@ 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 {

7
compiler/rustc_const_eval/src/interpret/memory.rs
View file

@ -877,12 +877,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
if let Some(fn_val) = self.get_fn_alloc(id) {
let align = match fn_val {
FnVal::Instance(instance) => {
// 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.
let fn_align = self.tcx.codegen_fn_attrs(instance.def_id()).alignment;
let global_align = self.tcx.sess.opts.unstable_opts.min_function_alignment;
Ord::max(global_align, fn_align).unwrap_or(Align::ONE)
self.tcx.codegen_fn_attrs(instance.def_id()).alignment.unwrap_or(Align::ONE)
}
// Machine-specific extra functions currently do not support alignment restrictions.
FnVal::Other(_) => Align::ONE,