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Auto merge of #117116 - calebzulawski:repr-simd-packed, r=workingjubilee

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Implement repr(packed) for repr(simd)

This allows creating vectors with non-power-of-2 lengths that do not have padding.  See rust-lang/portable-simd#319
This commit is contained in:
bors 2023-12-11 08:07:20 +00:00
commit 8b1ba11cb1
3 changed files with 83 additions and 3 deletions
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9
compiler/rustc_codegen_llvm/src/intrinsic.rs
View file

@ -10,7 +10,7 @@ use crate::value::Value;
use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh, wants_wasm_eh};
use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
use rustc_codegen_ssa::errors::{ExpectedPointerMutability, InvalidMonomorphization};
use rustc_codegen_ssa::mir::operand::OperandRef;
use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
use rustc_codegen_ssa::mir::place::PlaceRef;
use rustc_codegen_ssa::traits::*;
use rustc_hir as hir;
@ -946,6 +946,13 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), callee_ty.fn_sig(tcx));
let arg_tys = sig.inputs();
// Vectors must be immediates (non-power-of-2 #[repr(packed)] are not)
for (ty, arg) in arg_tys.iter().zip(args) {
if ty.is_simd() && !matches!(arg.val, OperandValue::Immediate(_)) {
return_error!(InvalidMonomorphization::SimdArgument { span, name, ty: *ty });
}
}
if name == sym::simd_select_bitmask {
let (len, _) = require_simd!(arg_tys[1], SimdArgument);

18
compiler/rustc_ty_utils/src/layout.rs
View file

@ -433,7 +433,21 @@ fn layout_of_uncached<'tcx>(
.size
.checked_mul(e_len, dl)
.ok_or_else(|| error(cx, LayoutError::SizeOverflow(ty)))?;
let align = dl.vector_align(size);
let (abi, align) = if def.repr().packed() && !e_len.is_power_of_two() {
// Non-power-of-two vectors have padding up to the next power-of-two.
// If we're a packed repr, remove the padding while keeping the alignment as close
// to a vector as possible.
(
Abi::Aggregate { sized: true },
AbiAndPrefAlign {
abi: Align::max_for_offset(size),
pref: dl.vector_align(size).pref,
},
)
} else {
(Abi::Vector { element: e_abi, count: e_len }, dl.vector_align(size))
};
let size = size.align_to(align.abi);
// Compute the placement of the vector fields:
@ -446,7 +460,7 @@ fn layout_of_uncached<'tcx>(
tcx.mk_layout(LayoutS {
variants: Variants::Single { index: FIRST_VARIANT },
fields,
abi: Abi::Vector { element: e_abi, count: e_len },
abi,
largest_niche: e_ly.largest_niche,
size,
align,