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Windows x86: Change i128 to return via the vector ABI #134290

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20 changes: 13 additions & 7 deletions compiler/rustc_target/src/callconv/x86_win64.rs
Original file line number Diff line number Diff line change
@@ -1,12 +1,12 @@
use rustc_abi::{BackendRepr, Float, Primitive};
use rustc_abi::{BackendRepr, Float, Integer, Primitive, RegKind, Size};

use crate::abi::call::{ArgAbi, FnAbi, Reg};
use crate::spec::HasTargetSpec;

// Win64 ABI: https://docs.microsoft.com/en-us/cpp/build/parameter-passing

pub(crate) fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'_, Ty>) {
let fixup = |a: &mut ArgAbi<'_, Ty>| {
let fixup = |a: &mut ArgAbi<'_, Ty>, is_ret: bool| {
match a.layout.backend_repr {
BackendRepr::Uninhabited | BackendRepr::Memory { sized: false } => {}
BackendRepr::ScalarPair(..) | BackendRepr::Memory { sized: true } => {
Expand All @@ -23,11 +23,16 @@ pub(crate) fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'
// (probably what clang calls "illegal vectors").
}
BackendRepr::Scalar(scalar) => {
// Match what LLVM does for `f128` so that `compiler-builtins` builtins match up
// with what LLVM expects.
if a.layout.size.bytes() > 8
if is_ret && matches!(scalar.primitive(), Primitive::Int(Integer::I128, _)) {
// `i128` is returned in xmm0 by Clang and GCC, no
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no?

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Oops, no clue where I was going with that. Will fix.

// 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.
a.make_indirect();
} else {
a.extend_integer_width_to(32);
Expand All @@ -37,8 +42,9 @@ pub(crate) fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'
};

if !fn_abi.ret.is_ignore() {
fixup(&mut fn_abi.ret);
fixup(&mut fn_abi.ret, true);
}

for arg in fn_abi.args.iter_mut() {
if arg.is_ignore() {
// x86_64-pc-windows-gnu doesn't ignore ZSTs.
Expand All @@ -50,6 +56,6 @@ pub(crate) fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'
}
continue;
}
fixup(arg);
fixup(arg, false);
}
}
5 changes: 4 additions & 1 deletion tests/auxiliary/minicore.rs
Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,11 @@ impl<T: ?Sized> LegacyReceiver for &mut T {}
pub trait Copy: Sized {}

impl_marker_trait!(
Copy => [ bool, char, isize, usize, i8, i16, i32, i64, u8, u16, u32, u64, f32, f64 ]
Copy => [
bool, char, isize, usize, i8, i16, i32, i64, i128, u8, u16, u32, u64, u128, f32, f64
]
);

impl<'a, T: ?Sized> Copy for &'a T {}
impl<T: ?Sized> Copy for *const T {}
impl<T: ?Sized> Copy for *mut T {}
Expand Down
76 changes: 76 additions & 0 deletions tests/codegen/i128-x86-callconv.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,76 @@
//! Verify that Rust implements the expected calling convention for `i128`/`u128`.

//@ revisions: MSVC MINGW
//@ add-core-stubs
//@ [MSVC] needs-llvm-components: x86
//@ [MINGW] needs-llvm-components: x86
//@ [MSVC] compile-flags: --target x86_64-pc-windows-msvc
//@ [MINGW] compile-flags: --target x86_64-pc-windows-gnu
//@ [MSVC] filecheck-flags: --check-prefix=WIN
//@ [MINGW] filecheck-flags: --check-prefix=WIN

#![crate_type = "lib"]
#![no_std]
#![no_core]
#![feature(no_core, lang_items)]

extern crate minicore;

extern "C" {
fn extern_call(arg0: i128);
fn extern_ret() -> i128;
}

#[no_mangle]
pub extern "C" fn pass(_arg0: u32, arg1: i128) {
// CHECK-LABEL: @pass(
// i128 is passed indirectly on Windows. It should load the pointer to the stack and pass
// a pointer to that allocation.
// WIN-SAME: %_arg0, ptr{{.*}} %arg1)
// WIN: [[PASS:%[_0-9]+]] = alloca [16 x i8], align 16
// WIN: [[LOADED:%[_0-9]+]] = load i128, ptr %arg1
// WIN: store i128 [[LOADED]], ptr [[PASS]]
// WIN: call void @extern_call
unsafe { extern_call(arg1) };
}

// Check that we produce the correct return ABI
#[no_mangle]
pub extern "C" fn ret(_arg0: u32, arg1: i128) -> i128 {
// CHECK-LABEL: @ret(
// i128 is returned in xmm0 on Windows
// FIXME(#134288): This may change for the `-msvc` targets in the future.
// WIN-SAME: i32{{.*}} %_arg0, ptr{{.*}} %arg1)
// WIN: [[LOADED:%[_0-9]+]] = load <16 x i8>, ptr %arg1
// WIN-NEXT: ret <16 x i8> [[LOADED]]
arg1
}

// Check that we consume the correct return ABI
#[no_mangle]
pub extern "C" fn forward(dst: *mut i128) {
// CHECK-LABEL: @forward
// WIN-SAME: ptr{{.*}} %dst)
// WIN: [[RETURNED:%[_0-9]+]] = tail call <16 x i8> @extern_ret()
// WIN: store <16 x i8> [[RETURNED]], ptr %dst
// WIN: ret void
unsafe { *dst = extern_ret() };
}

#[repr(C)]
struct RetAggregate {
a: i32,
b: i128,
}

#[no_mangle]
pub extern "C" fn ret_aggregate(_arg0: u32, arg1: i128) -> RetAggregate {
// CHECK-LABEL: @ret_aggregate(
// Aggregates should also be returned indirectly
// WIN-SAME: ptr{{.*}}sret([32 x i8]){{.*}}[[RET:%[_0-9]+]], i32{{.*}}%_arg0, ptr{{.*}}%arg1)
// WIN: [[LOADED:%[_0-9]+]] = load i128, ptr %arg1
// WIN: [[GEP:%[_0-9]+]] = getelementptr{{.*}}, ptr [[RET]]
// WIN: store i128 [[LOADED]], ptr [[GEP]]
// WIN: ret void
RetAggregate { a: 1, b: arg1 }
}
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