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Revert "Auto merge of #113166 - moulins:ref-niches-initial, r=oli-obk"

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This reverts commit 557359f925, reversing
changes made to 1e6c09a803.
This commit is contained in:
David Tolnay
2023-07-21 22:35:57 -07:00
parent a5e2eca40e
commit 5bbf0a8306
48 changed files with 296 additions and 1067 deletions
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24
compiler/rustc_const_eval/src/interpret/discriminant.rs
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@@ -2,7 +2,8 @@
use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt};
use rustc_middle::{mir, ty};
use rustc_target::abi::{self, TagEncoding, VariantIdx, Variants, WrappingRange};
use rustc_target::abi::{self, TagEncoding};
use rustc_target::abi::{VariantIdx, Variants};
use super::{ImmTy, InterpCx, InterpResult, Machine, OpTy, PlaceTy, Scalar};
@@ -179,24 +180,19 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
// discriminant (encoded in niche/tag) and variant index are the same.
let variants_start = niche_variants.start().as_u32();
let variants_end = niche_variants.end().as_u32();
let variants_len = u128::from(variants_end - variants_start);
let variant = match tag_val.try_to_int() {
Err(dbg_val) => {
// So this is a pointer then, and casting to an int failed.
// Can only happen during CTFE.
// The pointer and niches ranges must be disjoint, then we know
// this is the untagged variant (as the value is not in the niche).
// Everything else, we conservatively reject.
let range = self.ptr_scalar_range(tag_val)?;
let niches = WrappingRange {
start: niche_start,
end: niche_start.wrapping_add(variants_len),
};
if niches.overlaps_range(range) {
// The niche must be just 0, and the ptr not null, then we know this is
// okay. Everything else, we conservatively reject.
let ptr_valid = niche_start == 0
&& variants_start == variants_end
&& !self.scalar_may_be_null(tag_val)?;
if !ptr_valid {
throw_ub!(InvalidTag(dbg_val))
} else {
untagged_variant
}
untagged_variant
}
Ok(tag_bits) => {
let tag_bits = tag_bits.assert_bits(tag_layout.size);
@@ -209,7 +205,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let variant_index_relative =
variant_index_relative_val.to_scalar().assert_bits(tag_val.layout.size);
// Check if this is in the range that indicates an actual discriminant.
if variant_index_relative <= variants_len {
if variant_index_relative <= u128::from(variants_end - variants_start) {
let variant_index_relative = u32::try_from(variant_index_relative)
.expect("we checked that this fits into a u32");
// Then computing the absolute variant idx should not overflow any more.