62fe055aba
Return values up to 128 bits in registers This fixes https://github.com/rust-lang/rust/issues/26494#issuecomment-619506345 by making Rust's default ABI pass return values up to 128 bits in size in registers, just like the System V ABI. The result is that these methods from the comment linked above now generate the same code, making the Rust ABI as efficient as the `"C"` ABI: ```rust pub struct Stats { x: u32, y: u32, z: u32, } pub extern "C" fn sum_c(a: &Stats, b: &Stats) -> Stats { return Stats {x: a.x + b.x, y: a.y + b.y, z: a.z + b.z }; } pub fn sum_rust(a: &Stats, b: &Stats) -> Stats { return Stats {x: a.x + b.x, y: a.y + b.y, z: a.z + b.z }; } ``` ```asm sum_rust: movl (%rsi), %eax addl (%rdi), %eax movl 4(%rsi), %ecx addl 4(%rdi), %ecx movl 8(%rsi), %edx addl 8(%rdi), %edx shlq $32, %rcx orq %rcx, %rax retq ``` |
||
|---|---|---|
| .. | ||
| benches | ||
| src | ||
| Cargo.toml | ||
| README.md | ||
For more information about how rustc works, see the rustc dev guide.