[lld] r302708 - Use a DenseMap in LinkerScript::getCmd.

[Rui Ueyama via llvm-commits]

Great improvement!

On Wed, May 10, 2017 at 12:13 PM, Rafael Espindola via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: rafael
> Date: Wed May 10 14:13:38 2017
> New Revision: 302708
>
> URL: http://llvm.org/viewvc/llvm-project?rev=302708&view=rev
> Log:
> Use a DenseMap in LinkerScript::getCmd.
>
> This improves many-sections.s with a linker script from 22s to 0.9s.
>
> Modified:
>     lld/trunk/ELF/LinkerScript.cpp
>     lld/trunk/ELF/LinkerScript.h
>     lld/trunk/test/ELF/many-sections.s
>
> Modified: lld/trunk/ELF/LinkerScript.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/
> LinkerScript.cpp?rev=302708&r1=302707&r2=302708&view=diff
> ============================================================
> ==================
> --- lld/trunk/ELF/LinkerScript.cpp (original)
> +++ lld/trunk/ELF/LinkerScript.cpp Wed May 10 14:13:38 2017
> @@ -415,6 +415,7 @@ void LinkerScript::processCommands(Outpu
>        if (OutputSection *Sec = Cmd->Sec) {
>          assert(Sec->SectionIndex == INT_MAX);
>          Sec->SectionIndex = I;
> +        SecToCommand[Sec] = Cmd;
>        }
>      }
>    }
> @@ -444,6 +445,7 @@ void LinkerScript::fabricateDefaultComma
>
>      auto *OSCmd = make<OutputSectionCommand>(Sec->Name);
>      OSCmd->Sec = Sec;
> +    SecToCommand[Sec] = OSCmd;
>
>      // Prefer user supplied address over additional alignment constraint
>      auto I = Config->SectionStartMap.find(Sec->Name);
> @@ -488,6 +490,7 @@ void LinkerScript::addOrphanSections(Out
>        auto *Cmd = cast<OutputSectionCommand>(*I);
>        Factory.addInputSec(S, Name, Cmd->Sec);
>        if (OutputSection *Sec = Cmd->Sec) {
> +        SecToCommand[Sec] = Cmd;
>          unsigned Index = std::distance(Opt.Commands.begin(), I);
>          assert(Sec->SectionIndex == INT_MAX || Sec->SectionIndex ==
> Index);
>          Sec->SectionIndex = Index;
> @@ -703,6 +706,7 @@ void LinkerScript::adjustSectionsBeforeS
>      OutSec->SectionIndex = I;
>      OutputSections->push_back(OutSec);
>      Cmd->Sec = OutSec;
> +    SecToCommand[OutSec] = Cmd;
>    }
>  }
>
> @@ -833,6 +837,7 @@ void LinkerScript::placeOrphanSections()
>        ++CmdIndex;
>
>        Cmd->Sec = Sec;
> +      SecToCommand[Sec] = Cmd;
>        auto *ISD = make<InputSectionDescription>("");
>        for (InputSection *IS : Sec->Sections)
>          ISD->Sections.push_back(IS);
> @@ -1025,12 +1030,11 @@ bool LinkerScript::ignoreInterpSection()
>    return true;
>  }
>
> -OutputSectionCommand *LinkerScript::getCmd(OutputSection *Sec) {
> -  for (BaseCommand *Base : Opt.Commands)
> -    if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
> -      if (Cmd->Sec == Sec)
> -        return Cmd;
> -  return nullptr;
> +OutputSectionCommand *LinkerScript::getCmd(OutputSection *Sec) const {
> +  auto I = SecToCommand.find(Sec);
> +  if (I == SecToCommand.end())
> +    return nullptr;
> +  return I->second;
>  }
>
>  Optional<uint32_t> LinkerScript::getFiller(OutputSection *Sec) {
>
> Modified: lld/trunk/ELF/LinkerScript.h
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/
> LinkerScript.h?rev=302708&r1=302707&r2=302708&view=diff
> ============================================================
> ==================
> --- lld/trunk/ELF/LinkerScript.h (original)
> +++ lld/trunk/ELF/LinkerScript.h Wed May 10 14:13:38 2017
> @@ -212,7 +212,8 @@ struct ScriptConfiguration {
>  };
>
>  class LinkerScript final {
> -  OutputSectionCommand *getCmd(OutputSection *Sec);
> +  llvm::DenseMap<OutputSection *, OutputSectionCommand *> SecToCommand;
> +  OutputSectionCommand *getCmd(OutputSection *Sec) const;
>    void assignSymbol(SymbolAssignment *Cmd, bool InSec);
>    void setDot(Expr E, const Twine &Loc, bool InSec);
>
>
> Modified: lld/trunk/test/ELF/many-sections.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/
> many-sections.s?rev=302708&r1=302707&r2=302708&view=diff
> ============================================================
> ==================
> --- lld/trunk/test/ELF/many-sections.s (original)
> +++ lld/trunk/test/ELF/many-sections.s Wed May 10 14:13:38 2017
> @@ -14,6 +14,11 @@
>  // RUN: ld.lld %t -o %t2
>  // RUN: llvm-readobj -t %t2 | FileCheck --check-prefix=LINKED %s
>
> +// Test also with a linker script.
> +// RUN: echo "SECTIONS { . = SIZEOF_HEADERS; .text : { *(.text) } }" >
> %t.script
> +// RUN: ld.lld -T %t.script %t -o %t2
> +// RUN: llvm-readobj -t %t2 | FileCheck --check-prefix=LINKED %s
> +
>  // Test that _start is in the correct section.
>  // LINKED:      Name: _start
>  // LINKED-NEXT: Value: 0x0
>
>
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