[lld] r233128 - PECOFF: Reduce import table size.

[Rui Ueyama]

The existing test cases using llvm-readobj should suffice. Output from
readobj didn't change, as the tool doesn't care whether or not the string
it's printing is an alias of something.

On Tue, Mar 24, 2015 at 4:21 PM, Rafael Espíndola <
rafael.espindola at gmail.com> wrote:

> testcase? :-)
>
> On 24 March 2015 at 18:43, Rui Ueyama <ruiu at google.com> wrote:
> > Author: ruiu
> > Date: Tue Mar 24 17:43:58 2015
> > New Revision: 233128
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=233128&view=rev
> > Log:
> > PECOFF: Reduce import table size.
> >
> > Import Lookup Table in Import Directory Table has the same contents
> > as Hint/Name Table. Symbol names imported from DLLs are pointed by
> > both Import Directory Table and Hint/Name Table. We had duplicate
> > strings there.
> >
> > This patch eliminates that duplication to make the table smaller.
> > This should reduce binary size by the sum of lengths of imported
> > symbols.
> >
> > Modified:
> >     lld/trunk/lib/ReaderWriter/PECOFF/IdataPass.cpp
> >
> > Modified: lld/trunk/lib/ReaderWriter/PECOFF/IdataPass.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/PECOFF/IdataPass.cpp?rev=233128&r1=233127&r2=233128&view=diff
> >
> ==============================================================================
> > --- lld/trunk/lib/ReaderWriter/PECOFF/IdataPass.cpp (original)
> > +++ lld/trunk/lib/ReaderWriter/PECOFF/IdataPass.cpp Tue Mar 24 17:43:58
> 2015
> > @@ -69,6 +69,7 @@ static std::vector<ImportTableEntryAtom
> >  createImportTableAtoms(IdataContext &context,
> >                         const std::vector<COFFSharedLibraryAtom *>
> &sharedAtoms,
> >                         bool shouldAddReference, StringRef sectionName,
> > +                       std::map<StringRef, HintNameAtom *>
> &hintNameCache,
> >                         llvm::BumpPtrAllocator &alloc) {
> >    std::vector<ImportTableEntryAtom *> ret;
> >    for (COFFSharedLibraryAtom *atom : sharedAtoms) {
> > @@ -81,9 +82,16 @@ createImportTableAtoms(IdataContext &con
> >      } else {
> >        // Import by name
> >        entry = new (alloc) ImportTableEntryAtom(context, 0, sectionName);
> > -      HintNameAtom *hintName =
> > -          new (alloc) HintNameAtom(context, atom->hint(),
> atom->importName());
> > -      addDir32NBReloc(entry, hintName, context.ctx.getMachineType(), 0);
> > +      HintNameAtom *hintNameAtom;
> > +      auto it = hintNameCache.find(atom->importName());
> > +      if (it == hintNameCache.end()) {
> > +        hintNameAtom = new (alloc) HintNameAtom(
> > +            context, atom->hint(), atom->importName());
> > +        hintNameCache[atom->importName()] = hintNameAtom;
> > +      } else {
> > +        hintNameAtom = it->second;
> > +      }
> > +      addDir32NBReloc(entry, hintNameAtom,
> context.ctx.getMachineType(), 0);
> >      }
> >      ret.push_back(entry);
> >      if (shouldAddReference)
> > @@ -104,10 +112,13 @@ void ImportDirectoryAtom::addRelocations
> >    // same. The PE/COFF loader overwrites the import address tables with
> the
> >    // pointers to the referenced items after loading the executable into
> >    // memory.
> > +  std::map<StringRef, HintNameAtom *> hintNameCache;
> >    std::vector<ImportTableEntryAtom *> importLookupTables =
> > -      createImportTableAtoms(context, sharedAtoms, false, ".idata.t",
> _alloc);
> > +      createImportTableAtoms(context, sharedAtoms, false, ".idata.t",
> > +                             hintNameCache, _alloc);
> >    std::vector<ImportTableEntryAtom *> importAddressTables =
> > -      createImportTableAtoms(context, sharedAtoms, true, ".idata.a",
> _alloc);
> > +      createImportTableAtoms(context, sharedAtoms, true, ".idata.a",
> > +                             hintNameCache, _alloc);
> >
> >    addDir32NBReloc(this, importLookupTables[0],
> context.ctx.getMachineType(),
> >                    offsetof(ImportDirectoryTableEntry,
> ImportLookupTableRVA));
> > @@ -157,8 +168,10 @@ void DelayImportDirectoryAtom::addReloca
> >    // as (non-delay) import table's Import Lookup Table. Contains
> >    // imported function names. This is a parallel array of AddressTable
> >    // field.
> > +  std::map<StringRef, HintNameAtom *> hintNameCache;
> >    std::vector<ImportTableEntryAtom *> nameTable =
> > -      createImportTableAtoms(context, sharedAtoms, false, ".didat",
> _alloc);
> > +      createImportTableAtoms(
> > +          context, sharedAtoms, false, ".didat", hintNameCache, _alloc);
> >    addDir32NBReloc(
> >        this, nameTable[0], context.ctx.getMachineType(),
> >        offsetof(delay_import_directory_table_entry,
> DelayImportNameTable));
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
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