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naked-functions: properly document the -Zfunction-sections windows status

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This commit is contained in:
Folkert de Vries
2026-01-17 13:30:47 +01:00
parent 25e1647869
commit bc4aad37ca
2 changed files with 54 additions and 20 deletions
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compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
+27 -5
View File
@@ -8,7 +8,7 @@
use rustc_middle::{bug, ty};
use rustc_span::sym;
use rustc_target::callconv::{ArgAbi, FnAbi, PassMode};
use rustc_target::spec::{Arch, BinaryFormat};
use rustc_target::spec::{Arch, BinaryFormat, Env};
use crate::common;
use crate::mir::AsmCodegenMethods;
@@ -234,6 +234,8 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, ".pushsection {section},\"ax\", {progbits}").unwrap();
} else if function_sections {
writeln!(begin, ".pushsection .text.{asm_name},\"ax\", {progbits}").unwrap();
} else {
writeln!(begin, ".text").unwrap();
}
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
@@ -261,7 +263,9 @@ fn prefix_and_suffix<'tcx>(
}
}
BinaryFormat::MachO => {
// NOTE: LLVM ignores `-Zfunction-sections` on macos.
// NOTE: LLVM ignores `-Zfunction-sections` on macos. Instead the Mach-O symbol
// subsection splitting feature is used, which can be enabled with the
// `.subsections_via_symbols` global directive. LLVM already enables this directive.
if let Some(section) = &link_section {
writeln!(begin, ".pushsection {section},regular,pure_instructions").unwrap();
}
@@ -289,9 +293,27 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, ".endef").unwrap();
if let Some(section) = &link_section {
writeln!(begin, ".pushsection {section},\"xr\"").unwrap()
} else if function_sections {
writeln!(begin, ".pushsection .text${asm_name},\"xr\"").unwrap()
writeln!(begin, ".section {section},\"xr\"").unwrap()
} else if !function_sections {
// Function sections are enabled by default on MSVC, but disabled by default on GNU.
writeln!(begin, ".text").unwrap();
} else {
// LLVM uses an extension to the section directive to support defining multiple
// sections with the same name and comdat. It adds `unique,<id>` at the end of the
// `.section` directive. We have no way of generating that unique ID here, so don't
// emit it.
//
// See https://llvm.org/docs/Extensions.html#id2.
match &tcx.sess.target.options.env {
Env::Gnu => {
writeln!(begin, ".section .text${asm_name},\"xr\",one_only,{asm_name}")
.unwrap();
}
Env::Msvc => {
writeln!(begin, ".section .text,\"xr\",one_only,{asm_name}").unwrap();
}
other => bug!("invalid coff env {other:?}"),
}
}
write_linkage(&mut begin).unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
tests/codegen-llvm/naked-fn/naked-functions.rs
+27 -15
View File
@@ -1,10 +1,17 @@
// ignore-tidy-linelength
//
//@ add-minicore
//@ revisions: linux win_x86_msvc win_x86_gnu win_i686_gnu macos thumb
//@ revisions: linux linux_no_function_sections macos thumb
//@ revisions: win_x86_msvc win_x86_gnu win_i686_gnu win_x86_gnu_function_sections
//
//@[linux] compile-flags: --target x86_64-unknown-linux-gnu
//@[linux] needs-llvm-components: x86
//@[linux_no_function_sections] compile-flags: --target x86_64-unknown-linux-gnu -Zfunction-sections=false
//@[linux_no_function_sections] needs-llvm-components: x86
//@[win_x86_gnu] compile-flags: --target x86_64-pc-windows-gnu
//@[win_x86_gnu] needs-llvm-components: x86
//@[win_x86_gnu_function_sections] compile-flags: --target x86_64-pc-windows-gnu -Zfunction-sections
//@[win_x86_gnu_function_sections] needs-llvm-components: x86
//@[win_x86_msvc] compile-flags: --target x86_64-pc-windows-msvc
//@[win_x86_msvc] needs-llvm-components: x86
//@[win_i686_gnu] compile-flags: --target i686-pc-windows-gnu
@@ -21,20 +28,22 @@
extern crate minicore;
use minicore::*;
// linux,win_x86,win_i686: .intel_syntax
// linux,win_x86_gnu,win_i686_gnu: .intel_syntax
//
// linux: .pushsection .text.naked_empty,\22ax\22, @progbits
// linux_no_function_sections: .text
// macos-NOT: .pushsection
//
// win_x86_msvc: .pushsection .text$naked_empty,\22xr\22
// win_x86_gnu-NOT: .pushsection
// win_i686_gnu-NOT: .pushsection
// win_x86_msvc: .section .text,\22xr\22,one_only,naked_empty
// win_x86_gnu_function_sections: .section .text$naked_empty,\22xr\22,one_only,naked_empty
// win_x86_gnu-NOT: .section
// win_i686_gnu-NOT: .section
//
// thumb: .pushsection .text.naked_empty,\22ax\22, %progbits
//
// linux, macos, thumb: .balign 4
//
// linux,thumb: .globl naked_empty
// linux,win_x86_gnu,thumb: .globl naked_empty
// macos: .globl _naked_empty
//
// CHECK-NOT: .private_extern
@@ -63,7 +72,7 @@
//
// CHECK-LABEL: naked_empty:
//
// linux,macos,win_x86,win_x86: ret
// linux,macos,win_x86_msvc,win_x86_gnu,win_i686_gnu: ret
// thumb: bx lr
//
// linux,windows,win_x86_msvc,thumb: .popsection
@@ -86,20 +95,22 @@ pub extern "C" fn naked_empty() {
}
}
// linux,win_x86,win_i686: .intel_syntax
// linux,win_x86_gnu,win_i686_gnu,win_x86_msvc: .intel_syntax
//
// linux: .pushsection .text.naked_with_args_and_return,\22ax\22, @progbits
// linux_no_function_sections: .text
// macos-NOT: .pushsection
//
// win_x86_msvc: .pushsection .text$naked_with_args_and_return,\22xr\22
// win_x86_gnu-NOT: .pushsection
// win_i686_gnu-NOT: .pushsection
// win_x86_msvc: .section .text,\22xr\22,one_only,naked_with_args_and_return
// win_x86_gnu_function_sections: .section .text$naked_with_args_and_return,\22xr\22,one_only,naked_with_args_and_return
// win_x86_gnu-NOT: .section
// win_i686_gnu-NOT: .section
//
// thumb: .pushsection .text.naked_with_args_and_return,\22ax\22, %progbits
//
// linux, macos, thumb: .balign 4
//
// linux,thumb: .globl naked_with_args_and_return
// linux,win_x86_gnu,win_x86_msvc,win_i686_gnu,thumb: .globl naked_with_args_and_return
// macos: .globl _naked_with_args_and_return
//
// CHECK-NOT: .private_extern
@@ -132,7 +143,7 @@ pub extern "C" fn naked_empty() {
// macos: add x0, x0, x1
// thumb: adds r0, r0, r1
//
// linux,macos,win_x86,win_i686: ret
// linux,macos,win_x86_msvc,win_x86_gnu,win_i686_gnu: ret
// thumb: bx lr
//
// linux,windows,win_x86_msvc,thumb: .popsection
@@ -158,9 +169,10 @@ pub extern "C" fn naked_with_args_and_return(a: isize, b: isize) -> isize {
}
}
// linux: .pushsection .text.some_different_name,\22ax\22, @progbits
// linux,linux_no_function_sections: .pushsection .text.some_different_name,\22ax\22, @progbits
// macos: .pushsection .text.some_different_name,regular,pure_instructions
// win_x86_msvc,win_x86_gnu,win_i686_gnu: .pushsection .text.some_different_name,\22xr\22
// win_x86_msvc,win_x86_gnu,win_i686_gnu: .section .text.some_different_name,\22xr\22
// win_x86_gnu_function_sections: .section .text.some_different_name,\22xr\22
// thumb: .pushsection .text.some_different_name,\22ax\22, %progbits
// CHECK-LABEL: test_link_section:
#[no_mangle]