[LLVMdev] Your commit 103140

[Duncan Sands]

Hi Chris, your commit 103140 broke PR397 for llvm-gcc (in LLVM 2.9) and
dragonegg.  In the PR, asm renaming creates two linkonce functions with
the same asm name (in the IR they are @"\01lstat64" and "@lstat64".  What
used to happen is that they were both output to the assembler file, both
with the name lstat64, exactly like GCC does.  The assembler and linker
are perfectly happy about this, presumably because the functions have weak
linkage.  What happens now is that compilation fails with "label emitted
multiple times to assembly file".

Do you agree that it is reasonable to support outputting multiple functions
with the same name, as long as they have weak linkage?

Ciao, Duncan.

PS: The alternative is to follow clang and have the front-end take care of
dropping one of the functions, rather than leaving it to the linker.

> Index: test/CodeGen/X86/label-redefinition.ll
> ===================================================================
> --- test/CodeGen/X86/label-redefinition.ll	(revision 0)
> +++ test/CodeGen/X86/label-redefinition.ll	(revision 103140)
> @@ -0,0 +1,15 @@
> +; PR7054
> +; RUN: not llc %s -o - |& grep {'_foo' label emitted multiple times to assembly}
> +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
> +target triple = "i386-apple-darwin10.0.0"
> +
> +define i32 @"\01_foo"() {
> +  unreachable
> +}
> +
> +define i32 @foo() {
> +entry:
> +  unreachable
> +}
> +
> +declare i32 @xstat64(i32, i8*, i8*)
> Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
> ===================================================================
> --- lib/CodeGen/AsmPrinter/AsmPrinter.cpp	(revision 103139)
> +++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp	(revision 103140)
> @@ -408,7 +408,13 @@
>  /// EmitFunctionEntryLabel - Emit the label that is the entrypoint for the
>  /// function.  This can be overridden by targets as required to do custom stuff.
>  void AsmPrinter::EmitFunctionEntryLabel() {
> -  OutStreamer.EmitLabel(CurrentFnSym);
> +  // The function label could have already been emitted if two symbols end up
> +  // conflicting due to asm renaming.  Detect this and emit an error.
> +  if (CurrentFnSym->isUndefined())
> +    return OutStreamer.EmitLabel(CurrentFnSym);
> +
> +  report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
> +                     "' label emitted multiple times to assembly file");
>  }
>