[llvm] r187656 - Bugfix for making the DWARF debug strings and labels to code emitted as secrel32 instead of long opcodes (only for coff). This makes them debuggable with GDB (with fix for 64bits msvc)

[David Blaikie]

On Fri, Aug 2, 2013 at 9:14 AM, Carlo Kok <ck at remobjects.com> wrote:
> Author: carlokok
> Date: Fri Aug  2 11:14:15 2013
> New Revision: 187656
>
> URL: http://llvm.org/viewvc/llvm-project?rev=187656&view=rev
> Log:
> Bugfix for making the DWARF debug strings and labels to code emitted as secrel32 instead of long opcodes (only for coff). This makes them debuggable with GDB (with fix for 64bits msvc)
>
> Added:
>     llvm/trunk/test/DebugInfo/X86/coff_relative_names.ll
> Modified:
>     llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp?rev=187656&r1=187655&r2=187656&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/AsmPrinter.cpp Fri Aug  2 11:14:15 2013
> @@ -1416,6 +1416,10 @@ void AsmPrinter::EmitLabelOffsetDifferen
>  void AsmPrinter::EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
>                                        unsigned Size)
>    const {
> +  if (MAI->needsDwarfSectionOffsetDirective() && Size == 4) { // secrel32 ONLY works for 32bits.

Have you/could you test this for 64 bit on Windows too? Rather than
having half an implementation leaving the next developer to ask "what
about 64 bit?" it'd be nice to implement the complete functionality if
possible.

> +    OutStreamer.EmitCOFFSecRel32(Label);
> +    return;
> +  }
>
>    // Emit Label+Offset (or just Label if Offset is zero)
>    const MCExpr *Expr = MCSymbolRefExpr::Create(Label, OutContext);
>
> Added: llvm/trunk/test/DebugInfo/X86/coff_relative_names.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/coff_relative_names.ll?rev=187656&view=auto
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/X86/coff_relative_names.ll (added)
> +++ llvm/trunk/test/DebugInfo/X86/coff_relative_names.ll Fri Aug  2 11:14:15 2013
> @@ -0,0 +1,40 @@
> +; RUN: llc -mtriple=i686-w64-mingw32 -filetype=asm -O0 < %s | FileCheck %s
> +
> +; CHECK:       .secrel32 Linfo_string0
> +; CHECK:       .secrel32 Linfo_string1
> +;
> +; generated from:
> +; clang -g -S -emit-llvm test.c -o test.ll
> +; int main()
> +; {
> +;      return 0;
> +; }
> +
> +; ModuleID = 'test.c'
> +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f80:128:128-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S32"
> +target triple = "i686-pc-win32"
> +
> +; Function Attrs: nounwind
> +define i32 @main() #0 {
> +entry:
> +  %retval = alloca i32, align 4
> +  store i32 0, i32* %retval
> +  ret i32 0, !dbg !10
> +}
> +
> +attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
> +
> +!llvm.dbg.cu = !{!0}
> +!llvm.module.flags = !{!9}
> +
> +!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.4 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [C:\Projects/test.c] [DW_LANG_C99]
> +!1 = metadata !{metadata !"test.c", metadata !"C:\5CProjects"}
> +!2 = metadata !{i32 0}
> +!3 = metadata !{metadata !4}
> +!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"main", metadata !"main", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 0, i1 false, i32 ()* @main, null, null, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 1] [def] [scope 2] [main]
> +!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [C:\Projects/test.c]
> +!6 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, i32 0} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
> +!7 = metadata !{metadata !8}
> +!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
> +!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 3}
> +!10 = metadata !{i32 3, i32 0, metadata !4, null}
>
>
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