[lld] r316251 - Don't call buildSectionOrder multiple times.
Rafael Avila de Espindola via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 20 17:22:33 PDT 2017
On the same machine gold takes about 0.7 seconds to link the kernel :-)
Cheers,
Rafael
Shoaib Meenai <smeenai at fb.com> writes:
> Rui had a talk on LLD at the developer meeting, and the talk included some
> link time numbers. The Linux kernel was the only instance of gold being faster
> than LLD, and a lot of people (including myself) were wondering why that was
> the case. This is awesome :)
>
> On 10/20/17, 5:05 PM, "llvm-commits on behalf of Rafael Espindola via llvm-commits" <llvm-commits-bounces at lists.llvm.org on behalf of llvm-commits at lists.llvm.org> wrote:
>
> Author: rafael
> Date: Fri Oct 20 17:05:01 2017
> New Revision: 316251
>
> URL: https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D316251-26view-3Drev&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=4IyeZA5wFDIztRZwT5Ikft6eluO180gbHODF81Mf3Ug&s=nNq0DR5WWlYGE3cjull_12CMiIvQooETqug4_X5eGLk&e=
> Log:
> Don't call buildSectionOrder multiple times.
>
> This takes linking the linux kernel from 1.52s to 0.58s.
>
> Modified:
> lld/trunk/ELF/InputSection.cpp
> lld/trunk/ELF/LinkerScript.cpp
> lld/trunk/ELF/LinkerScript.h
>
> Modified: lld/trunk/ELF/InputSection.cpp
> URL: https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_ELF_InputSection.cpp-3Frev-3D316251-26r1-3D316250-26r2-3D316251-26view-3Ddiff&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=4IyeZA5wFDIztRZwT5Ikft6eluO180gbHODF81Mf3Ug&s=Behy9uothqGelaSOG4LvVOUM2TN8W9eggw9YF8Vj97o&e=
> ==============================================================================
> --- lld/trunk/ELF/InputSection.cpp (original)
> +++ lld/trunk/ELF/InputSection.cpp Fri Oct 20 17:05:01 2017
> @@ -46,6 +46,10 @@ std::string lld::toString(const InputSec
> }
>
> DenseMap<SectionBase *, int> elf::buildSectionOrder() {
> + DenseMap<SectionBase *, int> SectionOrder;
> + if (Config->SymbolOrderingFile.empty())
> + return SectionOrder;
> +
> // Build a map from symbols to their priorities. Symbols that didn't
> // appear in the symbol ordering file have the lowest priority 0.
> // All explicitly mentioned symbols have negative (higher) priorities.
> @@ -55,7 +59,6 @@ DenseMap<SectionBase *, int> elf::buildS
> SymbolOrder.insert({S, Priority++});
>
> // Build a map from sections to their priorities.
> - DenseMap<SectionBase *, int> SectionOrder;
> for (InputFile *File : ObjectFiles) {
> for (SymbolBody *Body : File->getSymbols()) {
> auto *D = dyn_cast<DefinedRegular>(Body);
>
> Modified: lld/trunk/ELF/LinkerScript.cpp
> URL: https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_ELF_LinkerScript.cpp-3Frev-3D316251-26r1-3D316250-26r2-3D316251-26view-3Ddiff&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=4IyeZA5wFDIztRZwT5Ikft6eluO180gbHODF81Mf3Ug&s=Je_3iU9P1LF12KLZrW5An0DBWzvNjnYc1jc4UWEUv0g&e=
> ==============================================================================
> --- lld/trunk/ELF/LinkerScript.cpp (original)
> +++ lld/trunk/ELF/LinkerScript.cpp Fri Oct 20 17:05:01 2017
> @@ -274,9 +274,9 @@ static void sortInputSections(
>
> // Compute and remember which sections the InputSectionDescription matches.
> std::vector<InputSection *>
> -LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
> +LinkerScript::computeInputSections(const InputSectionDescription *Cmd,
> + const DenseMap<SectionBase *, int> &Order) {
> std::vector<InputSection *> Ret;
> - DenseMap<SectionBase *, int> Order = buildSectionOrder();
>
> // Collects all sections that satisfy constraints of Cmd.
> for (const SectionPattern &Pat : Cmd->SectionPatterns) {
> @@ -326,13 +326,13 @@ void LinkerScript::discard(ArrayRef<Inpu
> }
> }
>
> -std::vector<InputSection *>
> -LinkerScript::createInputSectionList(OutputSection &OutCmd) {
> +std::vector<InputSection *> LinkerScript::createInputSectionList(
> + OutputSection &OutCmd, const DenseMap<SectionBase *, int> &Order) {
> std::vector<InputSection *> Ret;
>
> for (BaseCommand *Base : OutCmd.SectionCommands) {
> if (auto *Cmd = dyn_cast<InputSectionDescription>(Base)) {
> - Cmd->Sections = computeInputSections(Cmd);
> + Cmd->Sections = computeInputSections(Cmd, Order);
> Ret.insert(Ret.end(), Cmd->Sections.begin(), Cmd->Sections.end());
> }
> }
> @@ -359,6 +359,7 @@ void LinkerScript::processSectionCommand
> Ctx = make_unique<AddressState>();
> Ctx->OutSec = Aether;
>
> + DenseMap<SectionBase *, int> Order = buildSectionOrder();
> // Add input sections to output sections.
> for (size_t I = 0; I < SectionCommands.size(); ++I) {
> // Handle symbol assignments outside of any output section.
> @@ -368,7 +369,7 @@ void LinkerScript::processSectionCommand
> }
>
> if (auto *Sec = dyn_cast<OutputSection>(SectionCommands[I])) {
> - std::vector<InputSection *> V = createInputSectionList(*Sec);
> + std::vector<InputSection *> V = createInputSectionList(*Sec, Order);
>
> // The output section name `/DISCARD/' is special.
> // Any input section assigned to it is discarded.
>
> Modified: lld/trunk/ELF/LinkerScript.h
> URL: https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_ELF_LinkerScript.h-3Frev-3D316251-26r1-3D316250-26r2-3D316251-26view-3Ddiff&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=4IyeZA5wFDIztRZwT5Ikft6eluO180gbHODF81Mf3Ug&s=pbQ0x-JYey0QxqiIAbrRNWhQ6PJLgAuj9Mu8zFqXRco&e=
> ==============================================================================
> --- lld/trunk/ELF/LinkerScript.h (original)
> +++ lld/trunk/ELF/LinkerScript.h Fri Oct 20 17:05:01 2017
> @@ -205,9 +205,12 @@ class LinkerScript final {
> void setDot(Expr E, const Twine &Loc, bool InSec);
>
> std::vector<InputSection *>
> - computeInputSections(const InputSectionDescription *);
> + computeInputSections(const InputSectionDescription *,
> + const llvm::DenseMap<SectionBase *, int> &Order);
>
> - std::vector<InputSection *> createInputSectionList(OutputSection &Cmd);
> + std::vector<InputSection *>
> + createInputSectionList(OutputSection &Cmd,
> + const llvm::DenseMap<SectionBase *, int> &Order);
>
> std::vector<size_t> getPhdrIndices(OutputSection *Sec);
>
>
>
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