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Block SIMD in transmute_immediate; delete OperandValueKind

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See conversation in <https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Is.20transmuting.20a.20.60T.60.20to.20.60Tx1.60.20.28one-element.20SIMD.20vector.29.20UB.3F/near/526262799>.
This commit is contained in:
Scott McMurray
2025-07-03 22:23:15 -07:00
parent da58c05131
commit 5292554337
6 changed files with 101 additions and 190 deletions
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11
compiler/rustc_codegen_ssa/src/mir/operand.rs
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@@ -346,6 +346,13 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
let val = if field.is_zst() {
OperandValue::ZeroSized
} else if let BackendRepr::SimdVector { .. } = self.layout.backend_repr {
// codegen_transmute_operand doesn't support SIMD, but since the previous
// check handled ZSTs, the only possible field access into something SIMD
// is to the `non_1zst_field` that's the same SIMD. (Other things, even
// just padding, would change the wrapper's representation type.)
assert_eq!(field.size, self.layout.size);
self.val
} else if field.size == self.layout.size {
assert_eq!(offset.bytes(), 0);
fx.codegen_transmute_operand(bx, *self, field).unwrap_or_else(|| {
@@ -606,10 +613,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, Result<V, abi::Scalar>> {
};
let mut update = |tgt: &mut Result<V, abi::Scalar>, src, from_scalar| {
let from_bty = bx.cx().type_from_scalar(from_scalar);
let to_scalar = tgt.unwrap_err();
let to_bty = bx.cx().type_from_scalar(to_scalar);
let imm = transmute_immediate(bx, src, from_scalar, from_bty, to_scalar, to_bty);
let imm = transmute_immediate(bx, src, from_scalar, to_scalar);
*tgt = Ok(imm);
};