dfdfaa1f04
Optimize DST field access
For
struct X<T: ?Sized>(T)
struct Y<T: ?Sized>(u8, T)
the offset of the unsized field is
0
mem::align_of_val(&self.1)
respectively. This patch changes the expression used to compute these
offsets so that the optimizer can perform this optimization.
Consider
```rust
fn f(x: &X<dyn Any>) -> &dyn Any {
&x.0
}
```
Before:
```asm
test:
movq %rsi, %rdx
movq 16(%rsi), %rax
leaq -1(%rax), %rcx
negq %rax
andq %rcx, %rax
addq %rdi, %rax
retq
```
After:
```asm
test:
movq %rsi, %rdx
movq %rdi, %rax
retq
```
|
||
|---|---|---|
| .. | ||
| analyze.rs | ||
| block.rs | ||
| constant.rs | ||
| coverageinfo.rs | ||
| debuginfo.rs | ||
| intrinsic.rs | ||
| mod.rs | ||
| operand.rs | ||
| place.rs | ||
| rvalue.rs | ||
| statement.rs | ||