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Returns values up to 2*usize by value

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This commit is contained in:
Jonas Schievink 2020-10-02 00:23:25 +02:00
parent 8fe73e80d7
commit b01694e0a2
2 changed files with 3 additions and 14 deletions
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5
compiler/rustc_middle/src/ty/layout.rs
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@ -2787,8 +2787,9 @@ where
_ => return, _ => return,
} }
let max_by_val_size = // Return structures up to 2 pointers in size by value, matching `ScalarPair`. LLVM
if is_ret { call::max_ret_by_val(cx) } else { Pointer.size(cx) }; // will usually return these in 2 registers, which is more efficient than by-ref.
let max_by_val_size = if is_ret { Pointer.size(cx) * 2 } else { Pointer.size(cx) };
let size = arg.layout.size; let size = arg.layout.size;
if arg.layout.is_unsized() || size > max_by_val_size { if arg.layout.is_unsized() || size > max_by_val_size {

12
compiler/rustc_target/src/abi/call/mod.rs
View File

@ -610,15 +610,3 @@ impl<'a, Ty> FnAbi<'a, Ty> {
Ok(()) Ok(())
} }
} }
/// Returns the maximum size of return values to be passed by value in the Rust ABI.
///
/// Return values beyond this size will use an implicit out-pointer instead.
pub fn max_ret_by_val<C: HasTargetSpec + HasDataLayout>(spec: &C) -> Size {
match spec.target_spec().arch.as_str() {
// System-V will pass return values up to 128 bits in RAX/RDX.
"x86_64" => Size::from_bits(128),
_ => spec.data_layout().pointer_size,
}
}