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Merge commit '3a9bf72932' into sync_cg_clif-2023-12-19

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bjorn3 2023-12-19 12:46:39 +00:00
commit d5c38ded26
13 changed files with 223 additions and 115 deletions
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110
compiler/rustc_codegen_cranelift/src/unsize.rs
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@ -2,6 +2,9 @@
//!
//! [`PointerCoercion::Unsize`]: `rustc_middle::ty::adjustment::PointerCoercion::Unsize`
use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
use crate::base::codegen_panic_nounwind;
use crate::prelude::*;
// Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/base.rs#L159-L307
@ -187,63 +190,113 @@ pub(crate) fn coerce_dyn_star<'tcx>(
// Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
pub(crate) fn size_and_align_of_dst<'tcx>(
pub(crate) fn size_and_align_of<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
layout: TyAndLayout<'tcx>,
info: Value,
info: Option<Value>,
) -> (Value, Value) {
assert!(layout.is_unsized() || layout.abi == Abi::Uninhabited);
match layout.ty.kind() {
if layout.is_sized() {
return (
fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64),
fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64),
);
}
let ty = layout.ty;
match ty.kind() {
ty::Dynamic(..) => {
// load size/align from vtable
(crate::vtable::size_of_obj(fx, info), crate::vtable::min_align_of_obj(fx, info))
(
crate::vtable::size_of_obj(fx, info.unwrap()),
crate::vtable::min_align_of_obj(fx, info.unwrap()),
)
}
ty::Slice(_) | ty::Str => {
let unit = layout.field(fx, 0);
// The info in this case is the length of the str, so the size is that
// times the unit size.
(
fx.bcx.ins().imul_imm(info, unit.size.bytes() as i64),
fx.bcx.ins().imul_imm(info.unwrap(), unit.size.bytes() as i64),
fx.bcx.ins().iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
)
}
_ => {
ty::Foreign(_) => {
let trap_block = fx.bcx.create_block();
let true_ = fx.bcx.ins().iconst(types::I8, 1);
let next_block = fx.bcx.create_block();
fx.bcx.ins().brif(true_, trap_block, &[], next_block, &[]);
fx.bcx.seal_block(trap_block);
fx.bcx.seal_block(next_block);
fx.bcx.switch_to_block(trap_block);
// `extern` type. We cannot compute the size, so panic.
let msg_str = with_no_visible_paths!({
with_no_trimmed_paths!({
format!("attempted to compute the size or alignment of extern type `{ty}`")
})
});
codegen_panic_nounwind(fx, &msg_str, None);
fx.bcx.switch_to_block(next_block);
// This function does not return so we can now return whatever we want.
let size = fx.bcx.ins().iconst(fx.pointer_type, 42);
let align = fx.bcx.ins().iconst(fx.pointer_type, 42);
(size, align)
}
ty::Adt(..) | ty::Tuple(..) => {
// First get the size of all statically known fields.
// Don't use size_of because it also rounds up to alignment, which we
// want to avoid, as the unsized field's alignment could be smaller.
assert!(!layout.ty.is_simd());
let i = layout.fields.count() - 1;
let sized_size = layout.fields.offset(i).bytes();
let unsized_offset_unadjusted = layout.fields.offset(i).bytes();
let unsized_offset_unadjusted =
fx.bcx.ins().iconst(fx.pointer_type, unsized_offset_unadjusted as i64);
let sized_align = layout.align.abi.bytes();
let sized_align = fx.bcx.ins().iconst(fx.pointer_type, sized_align as i64);
// Recurse to get the size of the dynamically sized field (must be
// the last field).
let field_layout = layout.field(fx, i);
let (unsized_size, mut unsized_align) = size_and_align_of_dst(fx, field_layout, info);
let (unsized_size, mut unsized_align) = size_and_align_of(fx, field_layout, info);
// FIXME (#26403, #27023): We should be adding padding
// to `sized_size` (to accommodate the `unsized_align`
// required of the unsized field that follows) before
// summing it with `sized_size`. (Note that since #26403
// is unfixed, we do not yet add the necessary padding
// here. But this is where the add would go.)
// # First compute the dynamic alignment
// Return the sum of sizes and max of aligns.
let size = fx.bcx.ins().iadd_imm(unsized_size, sized_size as i64);
// Packed types ignore the alignment of their fields.
if let ty::Adt(def, _) = layout.ty.kind() {
if def.repr().packed() {
unsized_align = sized_align;
// For packed types, we need to cap the alignment.
if let ty::Adt(def, _) = ty.kind() {
if let Some(packed) = def.repr().pack {
if packed.bytes() == 1 {
// We know this will be capped to 1.
unsized_align = fx.bcx.ins().iconst(fx.pointer_type, 1);
} else {
// We have to dynamically compute `min(unsized_align, packed)`.
let packed = fx.bcx.ins().iconst(fx.pointer_type, packed.bytes() as i64);
let cmp = fx.bcx.ins().icmp(IntCC::UnsignedLessThan, unsized_align, packed);
unsized_align = fx.bcx.ins().select(cmp, unsized_align, packed);
}
}
}
// Choose max of two known alignments (combined value must
// be aligned according to more restrictive of the two).
let cmp = fx.bcx.ins().icmp(IntCC::UnsignedGreaterThan, sized_align, unsized_align);
let align = fx.bcx.ins().select(cmp, sized_align, unsized_align);
let full_align = fx.bcx.ins().select(cmp, sized_align, unsized_align);
// # Then compute the dynamic size
// The full formula for the size would be:
// let unsized_offset_adjusted = unsized_offset_unadjusted.align_to(unsized_align);
// let full_size = (unsized_offset_adjusted + unsized_size).align_to(full_align);
// However, `unsized_size` is a multiple of `unsized_align`.
// Therefore, we can equivalently do the `align_to(unsized_align)` *after* adding `unsized_size`:
// let full_size = (unsized_offset_unadjusted + unsized_size).align_to(unsized_align).align_to(full_align);
// Furthermore, `align >= unsized_align`, and therefore we only need to do:
// let full_size = (unsized_offset_unadjusted + unsized_size).align_to(full_align);
let full_size = fx.bcx.ins().iadd(unsized_offset_unadjusted, unsized_size);
// Issue #27023: must add any necessary padding to `size`
// (to make it a multiple of `align`) before returning it.
@ -255,12 +308,13 @@ pub(crate) fn size_and_align_of_dst<'tcx>(
// emulated via the semi-standard fast bit trick:
//
// `(size + (align-1)) & -align`
let addend = fx.bcx.ins().iadd_imm(align, -1);
let add = fx.bcx.ins().iadd(size, addend);
let neg = fx.bcx.ins().ineg(align);
let size = fx.bcx.ins().band(add, neg);
let addend = fx.bcx.ins().iadd_imm(full_align, -1);
let add = fx.bcx.ins().iadd(full_size, addend);
let neg = fx.bcx.ins().ineg(full_align);
let full_size = fx.bcx.ins().band(add, neg);
(size, align)
(full_size, full_align)
}
_ => bug!("size_and_align_of_dst: {ty} not supported"),
}
}