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test #[naked] with #[link_section = "..."] on windows #154598

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21 changes: 13 additions & 8 deletions compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -141,8 +141,14 @@ fn prefix_and_suffix<'tcx>(
let attrs = tcx.codegen_instance_attrs(instance.def);
let link_section = attrs.link_section.map(|symbol| symbol.as_str().to_string());

// If no alignment is specified, an alignment of 4 bytes is used.
let align_bytes = attrs.alignment.map(|a| a.bytes()).unwrap_or(4);
// Pick a default alignment when the alignment is not explicitly specified.
let align_bytes = match attrs.alignment {
Some(align) => align.bytes(),
None => match asm_binary_format {
BinaryFormat::Coff => 16,
_ => 4,
},
};
Comment on lines +144 to +151
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@folkertdev folkertdev Mar 30, 2026

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I don't think this really matters but we may as well match LLVM


// In particular, `.arm` can also be written `.code 32` and `.thumb` as `.code 16`.
let (arch_prefix, arch_suffix) = if is_arm {
Expand Down Expand Up @@ -267,19 +273,18 @@ fn prefix_and_suffix<'tcx>(
}
}
BinaryFormat::Coff => {
let section = link_section.unwrap_or_else(|| format!(".text.{asm_name}"));
writeln!(begin, ".pushsection {},\"xr\"", section).unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
writeln!(begin, ".def {asm_name}").unwrap();
writeln!(begin, ".scl 2").unwrap();
writeln!(begin, ".type 32").unwrap();
writeln!(begin, ".endef").unwrap();

let section = link_section.unwrap_or_else(|| format!(".text.{asm_name}"));
writeln!(begin, ".pushsection {},\"xr\"", section).unwrap();
write_linkage(&mut begin).unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
Comment on lines -270 to +284
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@folkertdev folkertdev Mar 30, 2026

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This just got moved up so that .def comes before the .pushsection.

writeln!(begin, "{asm_name}:").unwrap();

writeln!(end).unwrap();
writeln!(end, ".Lfunc_end_{asm_name}:").unwrap();
writeln!(end, ".popsection").unwrap();
Comment on lines -281 to -282
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@folkertdev folkertdev Mar 30, 2026

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LLVM does not emit these, so then we should not need to either

if !arch_suffix.is_empty() {
writeln!(end, "{}", arch_suffix).unwrap();
}
Expand Down
49 changes: 49 additions & 0 deletions tests/assembly-llvm/naked-functions/link-section-windows.rs
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@@ -0,0 +1,49 @@
//@ revisions: windows-x86-gnu windows-x86-msvc
//@ add-minicore
//@ assembly-output: emit-asm
//
//@[windows-x86-gnu] compile-flags: --target x86_64-pc-windows-gnu
//@[windows-x86-gnu] needs-llvm-components: x86
//
//@[windows-x86-msvc] compile-flags: --target x86_64-pc-windows-msvc
//@[windows-x86-msvc] needs-llvm-components: x86

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

// Tests that naked and non-naked functions emit the same directives when the function uses
// `#[link_section = "..."]`.

extern crate minicore;
use minicore::*;

#[unsafe(naked)]
#[unsafe(no_mangle)]
#[unsafe(link_section = "naked")]
extern "C" fn naked_ret() {
// CHECK: .def naked_ret;
// CHECK-NEXT: .scl 2;
// CHECK-NEXT: .type 32;
// CHECK-NEXT: .endef
// CHECK-NEXT: .section naked,"xr"
// CHECK-NEXT: .globl naked_ret
// CHECK-NEXT: .p2align 4
// CHECK-NEXT: naked_ret:
// CHECK-NEXT: retq
naked_asm!("ret")
}

#[unsafe(no_mangle)]
#[unsafe(link_section = "regular")]
extern "C" fn regular_ret() {
// CHECK: .def regular_ret;
// CHECK-NEXT: .scl 2;
// CHECK-NEXT: .type 32;
// CHECK-NEXT: .endef
// CHECK-NEXT: .section regular,"xr"
// CHECK-NEXT: .globl regular_ret
// CHECK-NEXT: .p2align 4
// CHECK-NEXT: regular_ret:
// CHECK-NEXT: retq
}
12 changes: 6 additions & 6 deletions tests/codegen-llvm/naked-fn/generics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,11 +19,11 @@ fn test(x: u64) {
foo.trait_method();
}

// CHECK: .balign 4
// CHECK: .balign
// CHECK: add rax, 1
// CHECK: add rax, 42

// CHECK: .balign 4
// CHECK: .balign
// CHECK: add rax, 2
// CHECK: add rax, 42

Expand Down Expand Up @@ -52,7 +52,7 @@ impl Invert for i64 {
}
}

// CHECK: .balign 4
// CHECK: .balign
// CHECK-LABEL: generic_function:
// CHECK: call
// CHECK: ret
Expand All @@ -71,7 +71,7 @@ pub extern "C" fn generic_function<T: Invert>(x: i64) -> i64 {
#[repr(transparent)]
struct Foo(u64);

// CHECK: .balign 4
// CHECK: .balign
// CHECK-LABEL: method:
// CHECK: mov rax, rdi

Expand All @@ -83,7 +83,7 @@ impl Foo {
}
}

// CHECK: .balign 4
// CHECK: .balign
// CHECK-LABEL: trait_method:
// CHECK: mov rax, rdi

Expand All @@ -99,7 +99,7 @@ impl Bar for Foo {
}
}

// CHECK: .balign 4
// CHECK: .balign
// CHECK-LABEL: naked_with_args_and_return:
// CHECK: lea rax, [rdi + rsi]

Expand Down
34 changes: 23 additions & 11 deletions tests/codegen-llvm/naked-fn/naked-functions.rs
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Expand Up @@ -23,13 +23,11 @@ use minicore::*;
//
// linux: .pushsection .text.naked_empty,\22ax\22, @progbits
// macos: .pushsection __TEXT,__text,regular,pure_instructions
// win_x86: .pushsection .text.naked_empty,\22xr\22
// win_i686: .pushsection .text._naked_empty,\22xr\22
// thumb: .pushsection .text.naked_empty,\22ax\22, %progbits
//
// CHECK: .balign 4
// linux, macos, thumb: .balign 4
//
// linux,win,thumb: .globl naked_empty
// linux,thumb: .globl naked_empty
// macos: .globl _naked_empty
//
// CHECK-NOT: .private_extern
Expand All @@ -44,16 +42,24 @@ use minicore::*;
// win_x86,win_i686: .type 32
// win_x86,win_i686: .endef
//
// win_x86: .pushsection .text.naked_empty,\22xr\22
// win_i686: .pushsection .text._naked_empty,\22xr\22
//
// win_x86: .globl naked_empty
// win_i686: .globl _naked_empty
//
// win_x86,win_i686: .balign 16
//
// thumb: .type naked_empty, %function
// thumb: .thumb
// thumb: .thumb_func
//
// CHECK-LABEL: naked_empty:
//
// linux,macos,win: ret
// linux,macos,win_x86,win_x86: ret
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@mati865 mati865 Mar 31, 2026

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You probably meant i686 and x86 here.

// thumb: bx lr
//
// CHECK: .popsection
// linux,macos,thumb: .popsection
//
// thumb: .thumb
//
Expand All @@ -76,13 +82,11 @@ pub extern "C" fn naked_empty() {
//
// linux: .pushsection .text.naked_with_args_and_return,\22ax\22, @progbits
// macos: .pushsection __TEXT,__text,regular,pure_instructions
// win_x86: .pushsection .text.naked_with_args_and_return,\22xr\22
// win_i686: .pushsection .text._naked_with_args_and_return,\22xr\22
// thumb: .pushsection .text.naked_with_args_and_return,\22ax\22, %progbits
//
// CHECK: .balign 4
// linux, macos, thumb: .balign 4
//
// linux,win,thumb: .globl naked_with_args_and_return
// linux,thumb: .globl naked_with_args_and_return
// macos: .globl _naked_with_args_and_return
//
// CHECK-NOT: .private_extern
Expand All @@ -97,6 +101,14 @@ pub extern "C" fn naked_empty() {
// win_x86,win_i686: .type 32
// win_x86,win_i686: .endef
//
// win_x86: .pushsection .text.naked_with_args_and_return,\22xr\22
// win_i686: .pushsection .text._naked_with_args_and_return,\22xr\22
//
// win_x86: .globl naked_with_args_and_return
// win_i686: .globl _naked_with_args_and_return
//
// win_x86,win_i686: .balign 16
//
// thumb: .type naked_with_args_and_return, %function
// thumb: .thumb
// thumb: .thumb_func
Expand All @@ -110,7 +122,7 @@ pub extern "C" fn naked_empty() {
// linux,macos,win: ret
// thumb: bx lr
//
// CHECK: .popsection
// linux,macos,thumb: .popsection
//
// thumb: .thumb
//
Expand Down
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