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Auto merge of #123351 - beetrees:x86-ret-snan-rust, r=nikic,workingjubilee

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Ensure floats are returned losslessly by the Rust ABI on 32-bit x86

Solves #115567 for the (default) `"Rust"` ABI. When compiling for 32-bit x86, this PR changes the `"Rust"` ABI to return floats indirectly instead of in x87 registers (with the exception of single `f32`s, which this PR returns in general purpose registers as they are small enough to fit in one). No change is made to the `"C"` ABI as that ABI requires x87 register usage and therefore will need a different solution.
This commit is contained in:
bors 2024-07-12 20:36:43 +00:00
commit c6727fc9b5
8 changed files with 461 additions and 10 deletions
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34
compiler/rustc_ty_utils/src/abi.rs
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@ -743,6 +743,40 @@ fn fn_abi_adjust_for_abi<'tcx>(
return;
}
// Avoid returning floats in x87 registers on x86 as loading and storing from x87
// registers will quiet signalling NaNs.
if cx.tcx.sess.target.arch == "x86"
&& arg_idx.is_none()
// Intrinsics themselves are not actual "real" functions, so theres no need to
// change their ABIs.
&& abi != SpecAbi::RustIntrinsic
{
match arg.layout.abi {
// Handle similar to the way arguments with an `Abi::Aggregate` abi are handled
// below, by returning arguments up to the size of a pointer (32 bits on x86)
// cast to an appropriately sized integer.
Abi::Scalar(s) if s.primitive() == Float(F32) => {
// Same size as a pointer, return in a register.
arg.cast_to(Reg::i32());
return;
}
Abi::Scalar(s) if s.primitive() == Float(F64) => {
// Larger than a pointer, return indirectly.
arg.make_indirect();
return;
}
Abi::ScalarPair(s1, s2)
if matches!(s1.primitive(), Float(F32 | F64))
|| matches!(s2.primitive(), Float(F32 | F64)) =>
{
// Larger than a pointer, return indirectly.
arg.make_indirect();
return;
}
_ => {}
};
}
match arg.layout.abi {
Abi::Aggregate { .. } => {}