bjoernager/rust
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copy byval argument to alloca if alignment is insufficient

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This commit is contained in:
Erik Desjardins 2024-03-08 17:11:27 -05:00
parent e919669d42
commit 207fe38630
3 changed files with 220 additions and 72 deletions
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60
compiler/rustc_codegen_ssa/src/mir/mod.rs
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@ -367,29 +367,45 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
}
}
if arg.is_sized_indirect() {
// Don't copy an indirect argument to an alloca, the caller
// already put it in a temporary alloca and gave it up.
// FIXME: lifetimes
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
} else if arg.is_unsized_indirect() {
// As the storage for the indirect argument lives during
// the whole function call, we just copy the fat pointer.
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
let llextra = bx.get_param(llarg_idx);
llarg_idx += 1;
let indirect_operand = OperandValue::Pair(llarg, llextra);
match arg.mode {
// Sized indirect arguments
PassMode::Indirect { attrs, meta_attrs: None, on_stack: _ } => {
// Don't copy an indirect argument to an alloca, the caller already put it
// in a temporary alloca and gave it up.
// FIXME: lifetimes
if let Some(pointee_align) = attrs.pointee_align
&& pointee_align < arg.layout.align.abi
{
// ...unless the argument is underaligned, then we need to copy it to
// a higher-aligned alloca.
let tmp = PlaceRef::alloca(bx, arg.layout);
bx.store_fn_arg(arg, &mut llarg_idx, tmp);
LocalRef::Place(tmp)
} else {
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
}
}
// Unsized indirect qrguments
PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
// As the storage for the indirect argument lives during
// the whole function call, we just copy the fat pointer.
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
let llextra = bx.get_param(llarg_idx);
llarg_idx += 1;
let indirect_operand = OperandValue::Pair(llarg, llextra);
let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
indirect_operand.store(bx, tmp);
LocalRef::UnsizedPlace(tmp)
} else {
let tmp = PlaceRef::alloca(bx, arg.layout);
bx.store_fn_arg(arg, &mut llarg_idx, tmp);
LocalRef::Place(tmp)
let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
indirect_operand.store(bx, tmp);
LocalRef::UnsizedPlace(tmp)
}
_ => {
let tmp = PlaceRef::alloca(bx, arg.layout);
bx.store_fn_arg(arg, &mut llarg_idx, tmp);
LocalRef::Place(tmp)
}
}
})
.collect::<Vec<_>>();