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naked_asm: emit a label starting with func_end

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The `cargo asm` tool pattern matches on such labels to figure out where functions end: normal functions generated by LLVM always do have such a label. We don't guarantee that naked functions emit such a label, but having `cargo asm` work is convenient
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Folkert de Vries 2025-09-19 21:53:06 +02:00
parent 8a1b39995e
commit b27942853e
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2 changed files with 7 additions and 0 deletions
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6
compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
View file

@ -228,6 +228,9 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, "{asm_name}:").unwrap();
writeln!(end).unwrap();
// emit a label starting with `func_end` for `cargo asm` and other tooling that might
// pattern match on assembly generated by LLVM.
writeln!(end, ".Lfunc_end_{asm_name}:").unwrap();
writeln!(end, ".size {asm_name}, . - {asm_name}").unwrap();
writeln!(end, ".popsection").unwrap();
if !arch_suffix.is_empty() {
@ -246,6 +249,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, "{asm_name}:").unwrap();
writeln!(end).unwrap();
writeln!(end, ".Lfunc_end_{asm_name}:").unwrap();
writeln!(end, ".popsection").unwrap();
if !arch_suffix.is_empty() {
writeln!(end, "{}", arch_suffix).unwrap();
@ -263,6 +267,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(begin, "{asm_name}:").unwrap();
writeln!(end).unwrap();
writeln!(end, ".Lfunc_end_{asm_name}:").unwrap();
writeln!(end, ".popsection").unwrap();
if !arch_suffix.is_empty() {
writeln!(end, "{}", arch_suffix).unwrap();
@ -287,6 +292,7 @@ fn prefix_and_suffix<'tcx>(
writeln!(end).unwrap();
// .size is ignored for function symbols, so we can skip it
writeln!(end, "end_function").unwrap();
writeln!(end, ".Lfunc_end_{asm_name}:").unwrap();
}
BinaryFormat::Xcoff => {
// the LLVM XCOFFAsmParser is extremely incomplete and does not implement many of the

1
tests/assembly-llvm/naked-functions/wasm32.rs
View file

@ -21,6 +21,7 @@ use minicore::*;
// CHECK: .functype nop () -> ()
// CHECK-NOT: .size
// CHECK: end_function
// CHECK-LABEL: .Lfunc_end_nop:
#[no_mangle]
#[unsafe(naked)]
extern "C" fn nop() {