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support XCOFF in naked_asm!

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Folkert de Vries 2025-02-28 19:30:01 +01:00
parent c620d76ae3
commit f35bda3997
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2 changed files with 76 additions and 9 deletions
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50
compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
View File

@ -125,7 +125,8 @@ fn prefix_and_suffix<'tcx>(
// the alignment from a `#[repr(align(<n>))]` is used if it specifies a higher alignment.
// if no alignment is specified, an alignment of 4 bytes is used.
let min_function_alignment = tcx.sess.opts.unstable_opts.min_function_alignment;
let align = Ord::max(min_function_alignment, attrs.alignment).map(|a| a.bytes()).unwrap_or(4);
let align_bytes =
Ord::max(min_function_alignment, attrs.alignment).map(|a| a.bytes()).unwrap_or(4);
// In particular, `.arm` can also be written `.code 32` and `.thumb` as `.code 16`.
let (arch_prefix, arch_suffix) = if is_arm {
@ -157,12 +158,16 @@ fn prefix_and_suffix<'tcx>(
}
Linkage::LinkOnceAny | Linkage::LinkOnceODR | Linkage::WeakAny | Linkage::WeakODR => {
match asm_binary_format {
BinaryFormat::Elf
| BinaryFormat::Coff
| BinaryFormat::Wasm
| BinaryFormat::Xcoff => {
BinaryFormat::Elf | BinaryFormat::Coff | BinaryFormat::Wasm => {
writeln!(w, ".weak {asm_name}")?;
}
BinaryFormat::Xcoff => {
// FIXME: there is currently no way of defining a weak symbol in inline assembly
// for AIX. See https://github.com/llvm/llvm-project/issues/130269
emit_fatal(
"cannot create weak symbols from inline assembly for this target",
)
}
BinaryFormat::MachO => {
writeln!(w, ".globl {asm_name}")?;
writeln!(w, ".weak_definition {asm_name}")?;
@ -189,7 +194,7 @@ fn prefix_and_suffix<'tcx>(
let mut begin = String::new();
let mut end = String::new();
match asm_binary_format {
BinaryFormat::Elf | BinaryFormat::Xcoff => {
BinaryFormat::Elf => {
let section = link_section.unwrap_or(format!(".text.{asm_name}"));
let progbits = match is_arm {
@ -203,7 +208,7 @@ fn prefix_and_suffix<'tcx>(
};
writeln!(begin, ".pushsection {section},\"ax\", {progbits}").unwrap();
writeln!(begin, ".balign {align}").unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
if let Visibility::Hidden = item_data.visibility {
writeln!(begin, ".hidden {asm_name}").unwrap();
@ -224,7 +229,7 @@ fn prefix_and_suffix<'tcx>(
BinaryFormat::MachO => {
let section = link_section.unwrap_or("__TEXT,__text".to_string());
writeln!(begin, ".pushsection {},regular,pure_instructions", section).unwrap();
writeln!(begin, ".balign {align}").unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
if let Visibility::Hidden = item_data.visibility {
writeln!(begin, ".private_extern {asm_name}").unwrap();
@ -240,7 +245,7 @@ fn prefix_and_suffix<'tcx>(
BinaryFormat::Coff => {
let section = link_section.unwrap_or(format!(".text.{asm_name}"));
writeln!(begin, ".pushsection {},\"xr\"", section).unwrap();
writeln!(begin, ".balign {align}").unwrap();
writeln!(begin, ".balign {align_bytes}").unwrap();
write_linkage(&mut begin).unwrap();
writeln!(begin, ".def {asm_name}").unwrap();
writeln!(begin, ".scl 2").unwrap();
@ -279,6 +284,33 @@ fn prefix_and_suffix<'tcx>(
// .size is ignored for function symbols, so we can skip it
writeln!(end, "end_function").unwrap();
}
BinaryFormat::Xcoff => {
// the LLVM XCOFFAsmParser is extremely incomplete and does not implement many of the
// documented directives.
//
// - https://github.com/llvm/llvm-project/blob/1b25c0c4da968fe78921ce77736e5baef4db75e3/llvm/lib/MC/MCParser/XCOFFAsmParser.cpp
// - https://www.ibm.com/docs/en/ssw_aix_71/assembler/assembler_pdf.pdf
//
// Consequently, we try our best here but cannot do as good a job as for other binary
// formats.
// FIXME: start a section. `.csect` is not currently implemented in LLVM
// fun fact: according to the assembler documentation, .align takes an exponent,
// but LLVM only accepts powers of 2 (but does emit the exponent)
// so when we hand `.align 32` to LLVM, the assembly output will contain `.align 5`
writeln!(begin, ".align {}", align_bytes).unwrap();
write_linkage(&mut begin).unwrap();
if let Visibility::Hidden = item_data.visibility {
// FIXME apparently `.globl {asm_name}, hidden` is valid
// but due to limitations with `.weak` (see above) we can't really use that in general yet
}
writeln!(begin, "{asm_name}:").unwrap();
writeln!(end).unwrap();
// FIXME: end the section?
}
}
(begin, end)

35
tests/assembly/naked-functions/aix.rs Normal file
View File

@ -0,0 +1,35 @@
//@ revisions: elfv1-be aix
//@ add-core-stubs
//@ assembly-output: emit-asm
//
//@[elfv1-be] compile-flags: --target powerpc64-unknown-linux-gnu
//@[elfv1-be] needs-llvm-components: powerpc
//
//@[aix] compile-flags: --target powerpc64-ibm-aix
//@[aix] needs-llvm-components: powerpc
#![crate_type = "lib"]
#![feature(no_core, naked_functions, asm_experimental_arch, f128, linkage, fn_align)]
#![no_core]
// tests that naked functions work for the `powerpc64-ibm-aix` target.
//
// This target is special because it uses the XCOFF binary format
// It is tested alongside an elf powerpc target to pin down commonalities and differences.
//
// https://doc.rust-lang.org/rustc/platform-support/aix.html
// https://www.ibm.com/docs/en/aix/7.2?topic=formats-xcoff-object-file-format
extern crate minicore;
use minicore::*;
// elfv1-be: .p2align 2
// aix: .align 2
// CHECK: .globl blr
// CHECK-LABEL: blr:
// CHECK: blr
#[no_mangle]
#[naked]
unsafe extern "C" fn blr() {
naked_asm!("blr")
}