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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 @@ fn adjust_for_abi(&mut self, cx: &C, abi: SpecAbi) {
_ => return,
}
let max_by_val_size =
if is_ret { call::max_ret_by_val(cx) } else { Pointer.size(cx) };
// Return structures up to 2 pointers in size by value, matching `ScalarPair`. LLVM
// 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;
if arg.layout.is_unsized() || size > max_by_val_size {

12
compiler/rustc_target/src/abi/call/mod.rs
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@ -610,15 +610,3 @@ pub fn adjust_for_cabi<C>(&mut self, cx: &C, abi: spec::abi::Abi) -> Result<(),
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,
}
}