[lld] r228377 - [ELF] Speedup creating program headers.

[Rui Ueyama]

On Thu, Feb 5, 2015 at 8:15 PM, Shankar Easwaran <shankare at codeaurora.org>
wrote:

> Author: shankare
> Date: Thu Feb  5 22:15:04 2015
> New Revision: 228377
>
> URL: http://llvm.org/viewvc/llvm-project?rev=228377&view=rev
> Log:
> [ELF] Speedup creating program headers.
>
> After the total number of program headers are determined, virtual addresses
> and file offsets need not be reassigned for sections whose virtual
> addresses and
> fileoffsets remained the same.
>
> This doesnot change any functionality.
>
> Modified:
>     lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h
>
> Modified: lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h?rev=228377&r1=228376&r2=228377&view=diff
>
> ==============================================================================
> --- lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h (original)
> +++ lld/trunk/lib/ReaderWriter/ELF/DefaultLayout.h Thu Feb  5 22:15:04 2015
> @@ -755,7 +755,7 @@ DefaultLayout<ELFT>::assignVirtualAddres
>
>    std::sort(_segments.begin(), _segments.end(),
> Segment<ELFT>::compareSegments);
>
> -  uint64_t virtualAddress = _context.getBaseAddress();
> +  uint64_t baseAddress = _context.getBaseAddress();
>
>    // HACK: This is a super dirty hack. The elf header and program header
> are
>    // not part of a section, but we need them to be loaded at the base
> address
> @@ -774,6 +774,7 @@ DefaultLayout<ELFT>::assignVirtualAddres
>    firstLoadSegment->prepend(_elfHeader);
>    bool newSegmentHeaderAdded = true;
>    bool virtualAddressAssigned = false;
> +  bool fileOffsetAssigned = false;
>    while (true) {
>      for (auto si : _segments) {
>        si->finalize();
> @@ -783,8 +784,8 @@ DefaultLayout<ELFT>::assignVirtualAddres
>      }
>      if (!newSegmentHeaderAdded && virtualAddressAssigned)
>        break;
> -    virtualAddressAssigned = true;
> -    uint64_t address = virtualAddress;
> +    uint64_t address = baseAddress;
> +    ;
>

Stray ';' here.


>      // start assigning virtual addresses
>      for (auto &si : _segments) {
>        if ((si->segmentType() != llvm::ELF::PT_LOAD) &&
> @@ -794,18 +795,27 @@ DefaultLayout<ELFT>::assignVirtualAddres
>        if (si->segmentType() == llvm::ELF::PT_NULL) {
>          si->assignVirtualAddress(0 /*non loadable*/);
>        } else {
> +        if (virtualAddressAssigned && (address != baseAddress) &&
> +            (address == si->virtualAddr()))
> +          break;
>          si->assignVirtualAddress(address);
>        }
>        address = si->virtualAddr() + si->memSize();
>      }
> -    uint64_t fileoffset = 0;
> +    uint64_t baseFileOffset = 0;
> +    uint64_t fileoffset = baseFileOffset;
>      for (auto &si : _segments) {
>        if ((si->segmentType() != llvm::ELF::PT_LOAD) &&
>            (si->segmentType() != llvm::ELF::PT_NULL))
>          continue;
> +      if (fileOffsetAssigned && (fileoffset != baseFileOffset) &&
> +          (fileoffset == si->fileOffset()))
> +        break;
>        si->assignFileOffsets(fileoffset);
>        fileoffset = si->fileOffset() + si->fileSize();
>      }
> +    virtualAddressAssigned = true;
> +    fileOffsetAssigned = true;
>      _programHeader->resetProgramHeaders();
>    }
>    Section<ELFT> *section;
>
>
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