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Rollup merge of #113529 - oli-obk:simd_shuffle_evaluated, r=wesleywiser

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Permit pre-evaluated constants in simd_shuffle

fixes https://github.com/rust-lang/rust/issues/113500
This commit is contained in:
Matthias Krüger 2023-07-20 17:19:32 +02:00 • committed by GitHub
commit 8c17e0701e
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2 changed files with 38 additions and 2 deletions
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16
compiler/rustc_codegen_ssa/src/mir/constant.rs
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@ -65,8 +65,22 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
&self,
constant: &mir::Constant<'tcx>,
) -> Result<Option<ty::ValTree<'tcx>>, ErrorHandled> {
let uv = match constant.literal {
let uv = match self.monomorphize(constant.literal) {
mir::ConstantKind::Unevaluated(uv, _) => uv.shrink(),
mir::ConstantKind::Ty(c) => match c.kind() {
// A constant that came from a const generic but was then used as an argument to old-style
// simd_shuffle (passing as argument instead of as a generic param).
rustc_type_ir::ConstKind::Value(valtree) => return Ok(Some(valtree)),
other => span_bug!(constant.span, "{other:#?}"),
},
// We should never encounter `ConstantKind::Val` unless MIR opts (like const prop) evaluate
// a constant and write that value back into `Operand`s. This could happen, but is unlikely.
// Also: all users of `simd_shuffle` are on unstable and already need to take a lot of care
// around intrinsics. For an issue to happen here, it would require a macro expanding to a
// `simd_shuffle` call without wrapping the constant argument in a `const {}` block, but
// the user pass through arbitrary expressions.
// FIXME(oli-obk): replace the magic const generic argument of `simd_shuffle` with a real
// const generic.
other => span_bug!(constant.span, "{other:#?}"),
};
let uv = self.monomorphize(uv);