[lld] r244904 - Store the offset in the output section, no in the file.

[Rui Ueyama via llvm-commits]

Can you make the same change for COFF so that the two are not going to
unnecessarily diverge?

On Fri, Aug 14, 2015 at 12:54 AM, Rafael Espindola via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: rafael
> Date: Thu Aug 13 10:54:36 2015
> New Revision: 244904
>
> URL: http://llvm.org/viewvc/llvm-project?rev=244904&view=rev
> Log:
> Store the offset in the output section, no in the file.
>
> That is the value that is stable as the we layout the output sections.
>
> Modified:
>     lld/trunk/ELF/Chunks.cpp
>     lld/trunk/ELF/Chunks.h
>     lld/trunk/ELF/Writer.cpp
>
> Modified: lld/trunk/ELF/Chunks.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Chunks.cpp?rev=244904&r1=244903&r2=244904&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Chunks.cpp (original)
> +++ lld/trunk/ELF/Chunks.cpp Thu Aug 13 10:54:36 2015
> @@ -33,7 +33,7 @@ template <class ELFT> void SectionChunk<
>      return;
>    // Copy section contents from source object file to output file.
>    ArrayRef<uint8_t> Data = *Obj->getSectionContents(Header);
> -  memcpy(Buf + FileOff, Data.data(), Data.size());
> +  memcpy(Buf + OutputSectionOff, Data.data(), Data.size());
>
>    // FIXME: Relocations
>  }
>
> Modified: lld/trunk/ELF/Chunks.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Chunks.h?rev=244904&r1=244903&r2=244904&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Chunks.h (original)
> +++ lld/trunk/ELF/Chunks.h Thu Aug 13 10:54:36 2015
> @@ -37,17 +37,18 @@ public:
>    virtual void writeTo(uint8_t *Buf) = 0;
>
>    // The writer sets and uses the addresses.
> -  uint64_t getFileOff() { return FileOff; }
> +  uint64_t getOutputSectionOff() { return OutputSectionOff; }
>    uint32_t getAlign() { return Align; }
> -  void setFileOff(uint64_t V) { FileOff = V; }
> +  void setOutputSectionOff(uint64_t V) { OutputSectionOff = V; }
>
>    // Returns the section name if this is a section chunk.
>    // It is illegal to call this function on non-section chunks.
>    virtual StringRef getSectionName() const = 0;
>
>  protected:
> -  // The offset from beginning of the output file. The writer sets a
> value.
> -  uint64_t FileOff = 0;
> +  // The offset from beginning of the output sections this chunk was
> assigned
> +  // to. The writer sets a value.
> +  uint64_t OutputSectionOff = 0;
>
>    // The alignment of this chunk. The writer uses the value.
>    uint32_t Align = 1;
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=244904&r1=244903&r2=244904&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Thu Aug 13 10:54:36 2015
> @@ -50,8 +50,8 @@ public:
>
>    // Returns the size of the section in the output file.
>    uintX_t getSize() { return Header.sh_size; }
> -
>    uintX_t getFlags() { return Header.sh_flags; }
> +  uintX_t getOffset() { return Header.sh_offset; }
>
>  private:
>    StringRef Name;
> @@ -122,8 +122,6 @@ template <class ELFT> void OutputSection
>    if (Header.sh_size == 0)
>      return;
>    Header.sh_offset = Off;
> -  for (Chunk *C : Chunks)
> -    C->setFileOff(C->getFileOff() + Off);
>  }
>
>  template <class ELFT>
> @@ -131,7 +129,7 @@ void OutputSection<ELFT>::addSectionChun
>    Chunks.push_back(C);
>    uintX_t Off = Header.sh_size;
>    Off = RoundUpToAlignment(Off, C->getAlign());
> -  C->setFileOff(Off);
> +  C->setOutputSectionOff(Off);
>    Off += C->getSize();
>    Header.sh_size = Off;
>    Header.sh_type = C->getSectionHdr()->sh_type;
> @@ -275,8 +273,9 @@ template <class ELFT> void Writer<ELFT>:
>  template <class ELFT> void Writer<ELFT>::writeSections() {
>    uint8_t *Buf = Buffer->getBufferStart();
>    for (OutputSection<ELFT> *Sec : OutputSections) {
> +    uint8_t *SecBuf = Buf + Sec->getOffset();
>      for (Chunk *C : Sec->getChunks())
> -      C->writeTo(Buf);
> +      C->writeTo(SecBuf);
>    }
>
>    // String table.
>
>
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