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[do not merge] Windows f128 abi experiment #137779

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[do not merge] Windows f128 abi experiment #137779

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4429a48
DO NOT MERGE change llvm module to my fork
tgross35 Feb 28, 2025
38c1ac9
Change the f128 ABI to match i128 on Windows
tgross35 Feb 28, 2025
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4 changes: 2 additions & 2 deletions .gitmodules
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,8 @@
shallow = true
[submodule "src/llvm-project"]
path = src/llvm-project
url = https://github.com/rust-lang/llvm-project.git
branch = rustc/20.1-2025-02-13
url = https://github.com/tgross35/llvm-project.git
branch = windows-f128-abi-combined
shallow = true
[submodule "src/doc/embedded-book"]
path = src/doc/embedded-book
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20 changes: 12 additions & 8 deletions compiler/rustc_target/src/callconv/x86_win64.rs
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Expand Up @@ -23,20 +23,24 @@ pub(crate) fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'
// (probably what clang calls "illegal vectors").
}
BackendRepr::Scalar(scalar) => {
if is_ret && matches!(scalar.primitive(), Primitive::Int(Integer::I128, _)) {
if is_ret
&& matches!(
scalar.primitive(),
Primitive::Int(Integer::I128, _) | Primitive::Float(Float::F128)
)
{
// i128 and f128 have the same ABI on Windows.
if cx.target_spec().rustc_abi == Some(RustcAbi::X86Softfloat) {
// Use the native `i128` LLVM type for the softfloat ABI -- in other words, adjust nothing.
// Use the native `i128`/`f128` LLVM type for the softfloat ABI -- in other
// words, adjust nothing.
} else {
// `i128` is returned in xmm0 by Clang and GCC
// `i128` and `f128` are returned in xmm0 by Clang. `i128` is returned in
// xmm0 by GCC but `f128` is indirect (Clang and GCC have a mismatch).
// FIXME(#134288): This may change for the `-msvc` targets in the future.
let reg = Reg { kind: RegKind::Vector, size: Size::from_bits(128) };
a.cast_to(reg);
}
} else if a.layout.size.bytes() > 8
&& !matches!(scalar.primitive(), Primitive::Float(Float::F128))
{
// Match what LLVM does for `f128` so that `compiler-builtins` builtins match up
// with what LLVM expects.
} else if a.layout.size.bytes() > 8 {
a.make_indirect();
} else {
a.extend_integer_width_to(32);
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2 changes: 1 addition & 1 deletion tests/assembly/x86_64-windows-float-abi.rs
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Expand Up @@ -37,7 +37,7 @@ pub extern "C" fn second_f64(_: f64, x: f64) -> f64 {
}

// CHECK-LABEL: second_f128
// CHECK: movaps %xmm1, %xmm0
// CHECK: movaps (%rdx), %xmm0
// CHECK-NEXT: retq
#[no_mangle]
pub extern "C" fn second_f128(_: f128, x: f128) -> f128 {
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