Rollup merge of #64149 - eddyb:llvm-var-names, r=rkruppe

rustc_codegen_llvm: give names to non-alloca variable values.

These names only matter when looking at LLVM IR, but they can help.

When one value is used for multiple variables, I decided to combine the names.
I chose `,` as a separator but maybe `=` or ` ` (space) are more appropriate.
(LLVM names can contain any characters - if necessary they end up having quotes)

As an example, this function:
```rust
#[no_mangle]
pub fn test(a: u32, b: u32) -> u32 {
    let c = a + b;
    let d = c;
    let e = d * a;
    e
}
```
Used to produce this LLVM IR:
```llvm
define i32 @test(i32 %a, i32 %b) unnamed_addr #0 {
start:
  %0 = add i32 %a, %b
  %1 = mul i32 %0, %a
  ret i32 %1
}
```
But after this PR you get this:
```llvm
define i32 @test(i32 %a, i32 %b) unnamed_addr #0 {
start:
  %"c,d" = add i32 %a, %b
  %e = mul i32 %"c,d", %a
  ret i32 %e
}
```

cc @nagisa @rkruppe

0 files changed, 0 insertions, 0 deletions