Do not spill operand debuginfo to stack for AArch64 SVE predicates <vscale x N x i1> where N != 16

[h3fang]

This pull request tries to fix #150419.

The debuginfo for AArch64 SVE predicates <vscale x N x i1> where N != 16 should be ignored by this commit.

rust/compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

Lines 438 to 452 in 89eea57

	if operand.layout.ty.is_scalable_vector()
	&& bx.sess().target.arch == rustc_target::spec::Arch::AArch64
	&& let ty::Adt(adt, args) = &operand.layout.ty.kind()
	&& let Some(marker_type_field) =
	adt.non_enum_variant().fields.get(FieldIdx::from_u32(0))
	{
	let marker_type = marker_type_field.ty(bx.tcx(), args);
	// i.e. `<vscale x N x i1>` when `N != 16`
	if let ty::Slice(element_ty) = marker_type.kind()
	&& element_ty.is_bool()
	&& adt.repr().scalable != Some(ScalableElt::ElementCount(16))
	{
	return;
	}
	}

But in line 446, the marker_type.kind() is ty::Bool instead of ty::Slice, so the code doesn't work as intended.

This pull request uses the Ty::scalable_vector_element_count_and_type method to fix the condition checks for <vscale x N x i1> where N != 16 and add a compiletest for this case.

[rustbot]

r? @dianqk

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[h3fang]

r? @davidtwco

[workingjubilee]

I have a few comments about comments and a minor quibble about where to put the test.

View changes since this review

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[h3fang]

@rustbot ready

[workingjubilee]

Excellent, excellent, happy to have it.

@bors r+ rollup

[bors]

📌 Commit 4c485a4 has been approved by workingjubilee

It is now in the queue for this repository.

[davidtwco]

Thanks for this fix @h3fang and for handling the review @workingjubilee!