[llvm] r179220 - Track the compact unwind encoding for when we are unable to generate compact unwind information.

[Bill Wendling]

So...basically, we should still emit a compact unwind encoding thing if we need to generate an EH frame. The encoding in that case will indicate this.

-bw

On Apr 10, 2013, at 2:42 PM, Bill Wendling <isanbard at gmail.com> wrote:

> Author: void
> Date: Wed Apr 10 16:42:06 2013
> New Revision: 179220
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=179220&view=rev
> Log:
> Track the compact unwind encoding for when we are unable to generate compact unwind information.
> 
> Compact unwind has an encoding for when we're not able to generate compact
> unwind and must generate an EH frame instead. Track that, but still emit that CU
> encoding.
> 
> Modified:
>    llvm/trunk/include/llvm/MC/MCObjectFileInfo.h
>    llvm/trunk/lib/MC/MCDwarf.cpp
>    llvm/trunk/lib/MC/MCObjectFileInfo.cpp
> 
> Modified: llvm/trunk/include/llvm/MC/MCObjectFileInfo.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCObjectFileInfo.h?rev=179220&r1=179219&r2=179220&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCObjectFileInfo.h (original)
> +++ llvm/trunk/include/llvm/MC/MCObjectFileInfo.h Wed Apr 10 16:42:06 2013
> @@ -46,10 +46,15 @@ protected:
>   unsigned FDEEncoding;
>   unsigned FDECFIEncoding;
>   unsigned TTypeEncoding;
> -  // Section flags for eh_frame
> +
> +  /// Section flags for eh_frame
>   unsigned EHSectionType;
>   unsigned EHSectionFlags;
> 
> +  /// CompactUnwindDwarfEHFrameOnly - Compact unwind encoding indicating that we
> +  /// should emit only an EH frame.
> +  unsigned CompactUnwindDwarfEHFrameOnly;
> +
>   /// TextSection - Section directive for standard text.
>   ///
>   const MCSection *TextSection;
> @@ -201,6 +206,10 @@ public:
>   }
>   unsigned getTTypeEncoding() const { return TTypeEncoding; }
> 
> +  unsigned getCompactUnwindDwarfEHFrameOnly() const {
> +    return CompactUnwindDwarfEHFrameOnly;
> +  }
> +
>   const MCSection *getTextSection() const { return TextSection; }
>   const MCSection *getDataSection() const { return DataSection; }
>   const MCSection *getBSSSection() const { return BSSSection; }
> 
> Modified: llvm/trunk/lib/MC/MCDwarf.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCDwarf.cpp?rev=179220&r1=179219&r2=179220&view=diff
> ==============================================================================
> --- llvm/trunk/lib/MC/MCDwarf.cpp (original)
> +++ llvm/trunk/lib/MC/MCDwarf.cpp Wed Apr 10 16:42:06 2013
> @@ -1168,10 +1168,10 @@ bool FrameEmitterImpl::EmitCompactUnwind
>   //   .quad except_tab1
> 
>   uint32_t Encoding = Frame.CompactUnwindEncoding;
> -  if (!Encoding) return false;
> +  bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
> 
>   // The encoding needs to know we have an LSDA.
> -  if (Frame.Lsda)
> +  if (!DwarfEHFrameOnly && Frame.Lsda)
>     Encoding |= 0x40000000;
> 
>   Streamer.SwitchSection(MOFI->getCompactUnwindSection());
> @@ -1194,11 +1194,10 @@ bool FrameEmitterImpl::EmitCompactUnwind
>                                       Twine::utohexstr(Encoding));
>   Streamer.EmitIntValue(Encoding, Size);
> 
> -
>   // Personality Function
>   Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
>   if (VerboseAsm) Streamer.AddComment("Personality Function");
> -  if (Frame.Personality)
> +  if (!DwarfEHFrameOnly && Frame.Personality)
>     Streamer.EmitSymbolValue(Frame.Personality, Size);
>   else
>     Streamer.EmitIntValue(0, Size); // No personality fn
> @@ -1206,7 +1205,7 @@ bool FrameEmitterImpl::EmitCompactUnwind
>   // LSDA
>   Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
>   if (VerboseAsm) Streamer.AddComment("LSDA");
> -  if (Frame.Lsda)
> +  if (!DwarfEHFrameOnly && Frame.Lsda)
>     Streamer.EmitSymbolValue(Frame.Lsda, Size);
>   else
>     Streamer.EmitIntValue(0, Size); // No LSDA
> 
> Modified: llvm/trunk/lib/MC/MCObjectFileInfo.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCObjectFileInfo.cpp?rev=179220&r1=179219&r2=179220&view=diff
> ==============================================================================
> --- llvm/trunk/lib/MC/MCObjectFileInfo.cpp (original)
> +++ llvm/trunk/lib/MC/MCObjectFileInfo.cpp Wed Apr 10 16:42:06 2013
> @@ -145,12 +145,16 @@ void MCObjectFileInfo::InitMachOMCObject
>   LSDASection = Ctx->getMachOSection("__TEXT", "__gcc_except_tab", 0,
>                                      SectionKind::getReadOnlyWithRel());
> 
> -  if (T.isMacOSX() && !T.isMacOSXVersionLT(10, 6))
> +  if (T.isMacOSX() && !T.isMacOSXVersionLT(10, 6)) {
>     CompactUnwindSection =
>       Ctx->getMachOSection("__LD", "__compact_unwind",
>                            MCSectionMachO::S_ATTR_DEBUG,
>                            SectionKind::getReadOnly());
> 
> +    if (T.getArch() == Triple::x86_64 || T.getArch() == Triple::x86)
> +      CompactUnwindDwarfEHFrameOnly = 0x04000000;
> +  }
> +
>   // Debug Information.
>   DwarfAccelNamesSection =
>     Ctx->getMachOSection("__DWARF", "__apple_names",
> @@ -629,6 +633,8 @@ void MCObjectFileInfo::InitMCObjectFileI
>   PersonalityEncoding = LSDAEncoding = FDEEncoding = FDECFIEncoding =
>     TTypeEncoding = dwarf::DW_EH_PE_absptr;
> 
> +  CompactUnwindDwarfEHFrameOnly = 0;
> +
>   EHFrameSection = 0;             // Created on demand.
>   CompactUnwindSection = 0;       // Used only by selected targets.
>   DwarfAccelNamesSection = 0;     // Used only by selected targets.
> 
> 
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