[llvm] r202357 - Don't emit anything into the debug_ranges section if we aren't emitting

[David Blaikie]

On Wed, Feb 26, 2014 at 11:44 PM, Eric Christopher <echristo at gmail.com> wrote:
> Author: echristo
> Date: Thu Feb 27 01:44:45 2014
> New Revision: 202357
>
> URL: http://llvm.org/viewvc/llvm-project?rev=202357&view=rev
> Log:
> Don't emit anything into the debug_ranges section if we aren't emitting
> any ranges - this includes CU ranges where we were previously emitting an
> end list marker even if we didn't have a list.
>
> Testcase includes a test for line table only code emission as the problem
> was noticed while writing this test.
>
> Added:
>     llvm/trunk/test/DebugInfo/cu-line-tables.ll
> Modified:
>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=202357&r1=202356&r2=202357&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Thu Feb 27 01:44:45 2014
> @@ -2873,7 +2873,7 @@ void DwarfDebug::emitDebugRanges() {
>      }
>
>      // Now emit a range for the CU itself.
> -    if (useCURanges()) {
> +    if (useCURanges() && TheCU->getRanges().size()) {

I assume the ranges is only non-empty if "useCURanges" is true, right?
So you can just test the latter condition and not the former?

(& if that relation isn't true (ie: we're adding ranges to the list
even when !useCURanges()) perhaps it should be so we don't spend time
needlessly populating the ranges list?)

>        Asm->OutStreamer.EmitLabel(
>            Asm->GetTempSymbol("cu_ranges", TheCU->getUniqueID()));
>        const SmallVectorImpl<RangeSpan> &Ranges = TheCU->getRanges();
>
> Added: llvm/trunk/test/DebugInfo/cu-line-tables.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/cu-line-tables.ll?rev=202357&view=auto
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/cu-line-tables.ll (added)
> +++ llvm/trunk/test/DebugInfo/cu-line-tables.ll Thu Feb 27 01:44:45 2014
> @@ -0,0 +1,50 @@
> +; REQUIRES: object-emission
> +; RUN: %llc_dwarf -O0 -filetype=obj -generate-dwarf-cu-ranges %s -o %t
> +; RUN: llvm-dwarfdump %t | FileCheck %s
> +
> +; Check that we don't emit ranges even if the option is passed if we're emitting line tables only.
> +
> +; CHECK: DW_TAG_compile_unit
> +; CHECK-NOT: DW_AT_ranges
> +; CHECK: DW_TAG_subprogram
> +
> +; FIXME: We probably want to avoid printing out anything if the section isn't there.
> +; CHECK: .debug_ranges contents:
> +; CHECK-NOT: 00000000 <End of list>
> +
> +; Function Attrs: nounwind uwtable
> +define i32 @f(i32 %a) #0 {
> +entry:
> +  %a.addr = alloca i32, align 4
> +  store i32 %a, i32* %a.addr, align 4
> +  call void @llvm.dbg.declare(metadata !{i32* %a.addr}, metadata !12), !dbg !13
> +  %0 = load i32* %a.addr, align 4, !dbg !14
> +  %add = add nsw i32 %0, 4, !dbg !14
> +  ret i32 %add, !dbg !14
> +}
> +
> +; Function Attrs: nounwind readnone
> +declare void @llvm.dbg.declare(metadata, metadata) #1
> +
> +attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
> +attributes #1 = { nounwind readnone }
> +
> +!llvm.dbg.cu = !{!0}
> +!llvm.module.flags = !{!9, !10}
> +!llvm.ident = !{!11}
> +
> +!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5 (trunk 197756) (llvm/trunk 197768)", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 2} ; [ DW_TAG_compile_unit ] [/usr/local/google/home/echristo/tmp/foo.c] [DW_LANG_C99]
> +!1 = metadata !{metadata !"foo.c", metadata !"/usr/local/google/home/echristo/tmp"}
> +!2 = metadata !{}
> +!3 = metadata !{metadata !4}
> +!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"f", metadata !"f", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (i32)* @f, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [f]
> +!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/usr/local/google/home/echristo/tmp/foo.c]
> +!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
> +!7 = metadata !{metadata !8, 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 4}
> +!10 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
> +!11 = metadata !{metadata !"clang version 3.5 (trunk 197756) (llvm/trunk 197768)"}
> +!12 = metadata !{i32 786689, metadata !4, metadata !"a", metadata !5, i32 16777217, metadata !8, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [a] [line 1]
> +!13 = metadata !{i32 1, i32 0, metadata !4, null}
> +!14 = metadata !{i32 2, i32 0, metadata !4, null}
>
>
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