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x86_64-win: Return f128 on the stack, matching LLVM #158918

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x86_64-win: Return f128 on the stack, matching LLVM #158918

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f05ac1d
tests: catch up with LLVM returning f128 on the stack
durin42 Jul 7, 2026
18ae03c
DO NOT MERGE merge https://github.com/rust-lang/rust/pull/158889
tgross35 Jul 7, 2026
04c6edd
x86_64-win: Return f128 on the stack, matching LLVM
tgross35 Jul 7, 2026
23a594c
x86_64-win: Enable f128 on LLVM 23+
tgross35 Jul 7, 2026
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9 changes: 6 additions & 3 deletions compiler/rustc_codegen_llvm/src/llvm_util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -369,7 +369,8 @@ fn update_target_reliable_float_cfg(sess: &Session, cfg: &mut TargetConfig) {
cfg.has_reliable_f16 = match (target_arch, target_os) {
// Unsupported <https://github.com/llvm/llvm-project/issues/94434> (fixed in llvm22)
(Arch::Arm64EC, _) if major < 22 => false,
// MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054>
// MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054> resolved in GCC 16
// but our toolchain hasn't been updated.
(Arch::X86_64, Os::Windows) if *target_env == Env::Gnu && *target_abi != CfgAbi::Llvm => {
false
}
Expand Down Expand Up @@ -397,8 +398,10 @@ fn update_target_reliable_float_cfg(sess: &Session, cfg: &mut TargetConfig) {
(Arch::PowerPC | Arch::PowerPC64, _) => false,
// ABI unsupported <https://github.com/llvm/llvm-project/issues/41838> (fixed in llvm22)
(Arch::Sparc, _) if major < 22 => false,
// MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054>
(Arch::X86_64, Os::Windows) if *target_env == Env::Gnu && *target_abi != CfgAbi::Llvm => {
// MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054> (fixed in llvm23)
(Arch::X86_64, Os::Windows)
if *target_env == Env::Gnu && *target_abi != CfgAbi::Llvm && major < 23 =>
{
false
}
// There are no known problems on other platforms, so the only requirement is that symbols
Expand Down
8 changes: 2 additions & 6 deletions compiler/rustc_target/src/callconv/x86_win64.rs
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@@ -1,4 +1,4 @@
use rustc_abi::{BackendRepr, Float, Integer, Primitive, Size, TyAbiInterface};
use rustc_abi::{BackendRepr, Integer, Primitive, Size, TyAbiInterface};

use crate::callconv::{ArgAbi, FnAbi, Reg};
use crate::spec::{HasTargetSpec, RustcAbi};
Expand Down Expand Up @@ -35,11 +35,7 @@ where
// FIXME(#134288): This may change for the `-msvc` targets in the future.
a.cast_to(Reg::opaque_vector(Size::from_bits(128)));
}
} 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);
Expand Down
4 changes: 3 additions & 1 deletion tests/assembly-llvm/x86_64-windows-float-abi.rs
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Expand Up @@ -37,7 +37,9 @@ pub extern "C" fn second_f64(_: f64, x: f64) -> f64 {
}

// CHECK-LABEL: second_f128
// CHECK: movaps (%rdx), %xmm0
// CHECK: movq %rcx, %rax
// CHECK-NEXT: movaps (%r8), %xmm0
// CHECK-NEXT: movaps %xmm0, (%rcx)
// CHECK-NEXT: retq
#[no_mangle]
pub extern "C" fn second_f128(_: f128, x: f128) -> f128 {
Expand Down
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