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Do not give function allocations alignment in consteval or miri.

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This commit is contained in:
Zachary S 2025-07-30 15:35:19 -05:00
parent 3fb1b53a9d
commit f554c79ef8
2 changed files with 6 additions and 27 deletions
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8
compiler/rustc_const_eval/src/interpret/memory.rs
View file

@ -937,8 +937,12 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
// (both global from `alloc_map` and local from `extra_fn_ptr_map`)
if let Some(fn_val) = self.get_fn_alloc(id) {
let align = match fn_val {
FnVal::Instance(instance) => {
self.tcx.codegen_instance_attrs(instance.def).alignment.unwrap_or(Align::ONE)
FnVal::Instance(_instance) => {
// FIXME: Until we have a clear design for the effects of align(N) functions
// on the address of function pointers, we don't consider the align(N)
// attribute on functions in the interpreter.
//self.tcx.codegen_instance_attrs(instance.def).alignment.unwrap_or(Align::ONE)
Align::ONE
}
// Machine-specific extra functions currently do not support alignment restrictions.
FnVal::Other(_) => Align::ONE,

25
src/tools/miri/tests/pass/fn_align.rs
View file

@ -1,25 +0,0 @@
//@compile-flags: -Zmin-function-alignment=8
// FIXME(rust-lang/rust#82232, rust-lang/rust#143834): temporarily renamed to mitigate `#[align]`
// nameres ambiguity
#![feature(rustc_attrs)]
#![feature(fn_align)]
// When a function uses `align(N)`, the function address should be a multiple of `N`.
#[rustc_align(256)]
fn foo() {}
#[rustc_align(16)]
fn bar() {}
#[rustc_align(4)]
fn baz() {}
fn main() {
assert!((foo as usize).is_multiple_of(256));
assert!((bar as usize).is_multiple_of(16));
// The maximum of `align(N)` and `-Zmin-function-alignment=N` is used.
assert!((baz as usize).is_multiple_of(8));
}