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Rollup merge of #132057 - RalfJung:miri-abi-compat, r=wesleywiser

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miri: update ABI compat checks to accept Option-like types

This implements the t-lang decision described [here](https://github.com/rust-lang/rust/pull/130628#issuecomment-2402761599).

Fixes https://github.com/rust-lang/miri/issues/3983
This commit is contained in:
Jonas Böttiger 2024-11-07 13:08:27 +01:00 • committed by GitHub
commit 6b5a58c265
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2 changed files with 60 additions and 19 deletions
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55
compiler/rustc_const_eval/src/interpret/call.rs
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@ -4,9 +4,9 @@ use std::assert_matches::assert_matches;
use std::borrow::Cow;
use either::{Left, Right};
use rustc_abi::{self as abi, ExternAbi, FieldIdx, Integer};
use rustc_abi::{self as abi, ExternAbi, FieldIdx, Integer, VariantIdx};
use rustc_middle::ty::layout::{FnAbiOf, IntegerExt, LayoutOf, TyAndLayout};
use rustc_middle::ty::{self, AdtDef, Instance, Ty};
use rustc_middle::ty::{self, AdtDef, Instance, Ty, VariantDef};
use rustc_middle::{bug, mir, span_bug};
use rustc_span::sym;
use rustc_target::callconv::{ArgAbi, FnAbi, PassMode};
@ -92,30 +92,47 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
/// Unwrap types that are guaranteed a null-pointer-optimization
fn unfold_npo(&self, layout: TyAndLayout<'tcx>) -> InterpResult<'tcx, TyAndLayout<'tcx>> {
// Check if this is `Option` wrapping some type or if this is `Result` wrapping a 1-ZST and
// another type.
// Check if this is an option-like type wrapping some type.
let ty::Adt(def, args) = layout.ty.kind() else {
// Not an ADT, so definitely no NPO.
return interp_ok(layout);
};
let inner = if self.tcx.is_diagnostic_item(sym::Option, def.did()) {
// The wrapped type is the only arg.
self.layout_of(args[0].as_type().unwrap())?
} else if self.tcx.is_diagnostic_item(sym::Result, def.did()) {
// We want to extract which (if any) of the args is not a 1-ZST.
let lhs = self.layout_of(args[0].as_type().unwrap())?;
let rhs = self.layout_of(args[1].as_type().unwrap())?;
if lhs.is_1zst() {
rhs
} else if rhs.is_1zst() {
lhs
} else {
return interp_ok(layout); // no NPO
if def.variants().len() != 2 {
// Not a 2-variant enum, so no NPO.
return interp_ok(layout);
}
assert!(def.is_enum());
let all_fields_1zst = |variant: &VariantDef| -> InterpResult<'tcx, _> {
for field in &variant.fields {
let ty = field.ty(*self.tcx, args);
let layout = self.layout_of(ty)?;
if !layout.is_1zst() {
return interp_ok(false);
}
}
} else {
return interp_ok(layout); // no NPO
interp_ok(true)
};
// If one variant consists entirely of 1-ZST, then the other variant
// is the only "relevant" one for this check.
let var0 = VariantIdx::from_u32(0);
let var1 = VariantIdx::from_u32(1);
let relevant_variant = if all_fields_1zst(def.variant(var0))? {
def.variant(var1)
} else if all_fields_1zst(def.variant(var1))? {
def.variant(var0)
} else {
// No varant is all-1-ZST, so no NPO.
return interp_ok(layout);
};
// The "relevant" variant must have exactly one field, and its type is the "inner" type.
if relevant_variant.fields.len() != 1 {
return interp_ok(layout);
}
let inner = relevant_variant.fields[FieldIdx::from_u32(0)].ty(*self.tcx, args);
let inner = self.layout_of(inner)?;
// Check if the inner type is one of the NPO-guaranteed ones.
// For that we first unpeel transparent *structs* (but not unions).
let is_npo = |def: AdtDef<'tcx>| {