[llvm] r210809 - [llvm-symbolizer] Fix parsing DW_AT_ranges in Fission skeleton compile unit DIEs.

[David Blaikie]

On Thu, Jun 12, 2014 at 11:52 AM, Alexey Samsonov <vonosmas at gmail.com> wrote:
> Author: samsonov
> Date: Thu Jun 12 13:52:35 2014
> New Revision: 210809
>
> URL: http://llvm.org/viewvc/llvm-project?rev=210809&view=rev
> Log:
> [llvm-symbolizer] Fix parsing DW_AT_ranges in Fission skeleton compile unit DIEs.
>
> Turns out that DW_AT_ranges_base attribute sets the offset for
> DW_AT_ranges values specified in the .dwo file, but not for DW_AT_ranges specified
> in the skeleton compile unit DIE in the main executable. This is extremely confusing,
> and would hopefully be fixed in DWARF-5 when it's finalized. For now this
> behavior makes sense, as otherwise Fission would break DWARF consumers who
> doesn't know anything about DW_AT_ranges_base.
>
>
> Added:
>     llvm/trunk/test/DebugInfo/Inputs/fission-ranges.cc
>     llvm/trunk/test/DebugInfo/Inputs/fission-ranges.elf-x86_64   (with props)
> Modified:
>     llvm/trunk/lib/DebugInfo/DWARFUnit.cpp
>     llvm/trunk/test/DebugInfo/llvm-symbolizer.test
>
> Modified: llvm/trunk/lib/DebugInfo/DWARFUnit.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/DebugInfo/DWARFUnit.cpp?rev=210809&r1=210808&r2=210809&view=diff
> ==============================================================================
> --- llvm/trunk/lib/DebugInfo/DWARFUnit.cpp (original)
> +++ llvm/trunk/lib/DebugInfo/DWARFUnit.cpp Thu Jun 12 13:52:35 2014
> @@ -225,8 +225,12 @@ size_t DWARFUnit::extractDIEsIfNeeded(bo
>      setBaseAddress(BaseAddr);
>      AddrOffsetSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
>          this, DW_AT_GNU_addr_base, 0);
> -    RangeSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
> -        this, DW_AT_GNU_ranges_base, 0);
> +    // Users of old DWARF may not know about DW_AT_ranges_base, so it is ignored
> +    // for skeleton CU DIE (e.g. DW_AT_ranges are *not* relative to it).
> +    if (Version > 4) {
> +      RangeSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
> +          this, DW_AT_GNU_ranges_base, 0);

In theory (I say in theory, because we haven't implemented this yet)
you shouldn't need to conditionalize by version, but just by attribute
name. DW_AT_GNU_ranges_base would be relative for only the things in
the dwo, and DW_AT_ranges_base will be relative for all the things in
the dwo and .o.

> +    }
>    }
>
>    setDIERelations();
> @@ -272,7 +276,9 @@ bool DWARFUnit::parseDWO() {
>    }
>    // Share .debug_addr and .debug_ranges section with compile unit in .dwo
>    DWOCU->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
> -  DWOCU->setRangesSection(RangeSection, RangeSectionBase);
> +  uint32_t DWORangesBase = DieArray[0].getAttributeValueAsSectionOffset(
> +      this, DW_AT_GNU_ranges_base, 0);
> +  DWOCU->setRangesSection(RangeSection, DWORangesBase);
>    return true;
>  }
>
>
> Added: llvm/trunk/test/DebugInfo/Inputs/fission-ranges.cc
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Inputs/fission-ranges.cc?rev=210809&view=auto
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/Inputs/fission-ranges.cc (added)
> +++ llvm/trunk/test/DebugInfo/Inputs/fission-ranges.cc Thu Jun 12 13:52:35 2014
> @@ -0,0 +1,17 @@
> +static inline int inlined_f() {
> +  volatile int x = 2;
> +  return x;
> +}
> +
> +int main() {
> +  return inlined_f();
> +}
> +
> +// Build instructions:
> +// $ mkdir /tmp/dbginfo
> +// $ cp fission-ranges.cc /tmp/dbginfo/
> +// $ cd /tmp/dbginfo
> +// $ gcc -gsplit-dwarf -O2 -fPIC fission-ranges.cc -c -o obj2.o
> +// $ clang -gsplit-dwarf -O2 -fsanitize=address -fPIC -Dmain=foo fission-ranges.cc -c -o obj1.o
> +// $ gcc obj1.o obj2.o -shared -o <output>
> +// $ objcopy --remove-section=.debug_aranges <output>
>
> Added: llvm/trunk/test/DebugInfo/Inputs/fission-ranges.elf-x86_64
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Inputs/fission-ranges.elf-x86_64?rev=210809&view=auto
> ==============================================================================
> Binary file - no diff available.
>
> Propchange: llvm/trunk/test/DebugInfo/Inputs/fission-ranges.elf-x86_64
> ------------------------------------------------------------------------------
>     svn:executable = *
>
> Propchange: llvm/trunk/test/DebugInfo/Inputs/fission-ranges.elf-x86_64
> ------------------------------------------------------------------------------
>     svn:mime-type = application/octet-stream
>
> Modified: llvm/trunk/test/DebugInfo/llvm-symbolizer.test
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/llvm-symbolizer.test?rev=210809&r1=210808&r2=210809&view=diff
> ==============================================================================
> --- llvm/trunk/test/DebugInfo/llvm-symbolizer.test (original)
> +++ llvm/trunk/test/DebugInfo/llvm-symbolizer.test Thu Jun 12 13:52:35 2014
> @@ -17,6 +17,7 @@ RUN: echo "%p/Inputs/macho-universal 0x1
>  RUN: echo "%p/Inputs/macho-universal:i386 0x1f67" >> %t.input
>  RUN: echo "%p/Inputs/macho-universal:x86_64 0x100000f05" >> %t.input
>  RUN: echo "%p/Inputs/llvm-symbolizer-dwo-test 0x400514" >> %t.input
> +RUN: echo "%p/Inputs/fission-ranges.elf-x86_64 0x720" >> %t.input
>
>  RUN: llvm-symbolizer --functions=linkage --inlining --demangle=false \
>  RUN:    --default-arch=i386 < %t.input | FileCheck %s
> @@ -90,6 +91,9 @@ CHECK:      _Z3inci
>  CHECK: main
>  CHECK-NEXT: llvm-symbolizer-dwo-test.cc:11
>
> +CHECK: main
> +CHECK-NEXT: {{.*}}fission-ranges.cc:6
> +
>  RUN: echo "unexisting-file 0x1234" > %t.input2
>  RUN: llvm-symbolizer < %t.input2
>
>
>
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