diff options
| -rw-r--r-- | compiler/rustc_codegen_ssa/src/mir/operand.rs | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs index eade9e52de9..29d030b7461 100644 --- a/compiler/rustc_codegen_ssa/src/mir/operand.rs +++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs @@ -45,9 +45,15 @@ pub enum OperandValue<V> { Immediate(V), /// A pair of immediate LLVM values. Used by wide pointers too. /// - /// An `OperandValue` *must* be this variant for any type for which + /// # Invariants + /// - For `Pair(a, b)`, `a` is always at offset 0, but may have `FieldIdx(1..)` + /// - `b` is not at offset 0, because `V` is not a 1ZST type. + /// - `a` and `b` will have a different FieldIdx, but otherwise `b`'s may be lower + /// or they may not be adjacent, due to arbitrary numbers of 1ZST fields that + /// will not affect the shape of the data which determines if `Pair` will be used. + /// - An `OperandValue` *must* be this variant for any type for which /// [`LayoutTypeCodegenMethods::is_backend_scalar_pair`] returns `true`. - /// The backend values in this variant must be the *immediate* backend types, + /// - The backend values in this variant must be the *immediate* backend types, /// as returned by [`LayoutTypeCodegenMethods::scalar_pair_element_backend_type`] /// with `immediate: true`. Pair(V, V), |