Still will not translate references to items like `X` or `Y::V` where
```
struct X;
enum Y { V }
```
but I must go work on university things so I’m PRing what I have.
r? @nikomatsakis
r? @nagisa
I'm going to need the `ConstVal` -> `ValueRef` translation to start removing trans/consts piece by piece. If you need anything implemented in the translation, feel free to assign an issue to me.
DST fields, being of an unknown type, are not automatically aligned
properly, so a pointer to the field needs to be aligned using the
information in the vtable.
Fixes#26403 and a number of other DST-related bugs discovered while
implementing this.
This PR allows the constant evaluation of index operations on constant arrays and repeat expressions. This allows index expressions to appear in the expression path of the length expression of a repeat expression or an array type.
An example is
```rust
const ARR: [usize; 5] = [1, 2, 3, 4, 5];
const ARR2: [usize; ARR[1]] = [42, 99];
```
In most other locations llvm's const evaluator figures it out already. This is not specific to index expressions and could be remedied in the future.
Introduce a `SwitchInt` and restructure pattern matching to collect integers and characters into one master switch. This is aimed at #29227, but is not a complete fix. Whereas before we generated an if-else-if chain and, at least on my machine, just failed to compile, we now spend ~9sec compiling `rustc_abuse`. AFAICT this is basically just due to a need for more micro-optimization of the matching process: perf shows a fair amount of time just spent iterating over the candidate list. Still, it seemed worth opening a PR with this step alone, since it's a big step forward.
Function arguments that are small aggregates get passed as integer types
instead. To correctly handle that, we need to use store_ty instead of
plain Store.
