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Allow Rvalue::Repeat to return true in rvalue_creates_operand too

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The conversation in 143502 made be realize how easy this is to handle, since the only possibilty is ZSTs -- everything else ends up with the destination being `LocalKind::Memory` and thus doesn't call `codegen_rvalue_operand` at all.

This gets us perilously close to a world where `rvalue_creates_operand` only ever returns true.  I'll try out such a world next :)
This commit is contained in:
Scott McMurray
2025-07-09 23:59:00 -07:00
parent f63685ddf3
commit 0586c63e07
2 changed files with 51 additions and 4 deletions
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16
compiler/rustc_codegen_ssa/src/mir/rvalue.rs
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@@ -630,7 +630,17 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
OperandRef { val: OperandValue::Immediate(static_), layout }
}
mir::Rvalue::Use(ref operand) => self.codegen_operand(bx, operand),
mir::Rvalue::Repeat(..) => bug!("{rvalue:?} in codegen_rvalue_operand"),
mir::Rvalue::Repeat(ref elem, len_const) => {
// All arrays have `BackendRepr::Memory`, so only the ZST cases
// end up here. Anything else forces the destination local to be
// `Memory`, and thus ends up handled in `codegen_rvalue` instead.
let operand = self.codegen_operand(bx, elem);
let array_ty = Ty::new_array_with_const_len(bx.tcx(), operand.layout.ty, len_const);
let array_ty = self.monomorphize(array_ty);
let array_layout = bx.layout_of(array_ty);
assert!(array_layout.is_zst());
OperandRef { val: OperandValue::ZeroSized, layout: array_layout }
}
mir::Rvalue::Aggregate(ref kind, ref fields) => {
let (variant_index, active_field_index) = match **kind {
mir::AggregateKind::Adt(_, variant_index, _, _, active_field_index) => {
@@ -1000,12 +1010,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mir::Rvalue::NullaryOp(..) |
mir::Rvalue::ThreadLocalRef(_) |
mir::Rvalue::Use(..) |
mir::Rvalue::Repeat(..) | // (*)
mir::Rvalue::Aggregate(..) | // (*)
mir::Rvalue::WrapUnsafeBinder(..) => // (*)
true,
// Arrays are always aggregates, so it's not worth checking anything here.
// (If it's really `[(); N]` or `[T; 0]` and we use the place path, fine.)
mir::Rvalue::Repeat(..) => false,
}
// (*) this is only true if the type is suitable