From 849d499e6d402f33c3e8e579476c3604d4cb1350 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Sat, 21 Oct 2017 00:05:01 +0000
Subject: [PATCH] Don't call buildSectionOrder multiple times.

This takes linking the linux kernel from 1.52s to 0.58s.

llvm-svn: 316251
---
 lld/ELF/InputSection.cpp |  5 ++++-
 lld/ELF/LinkerScript.cpp | 13 +++++++------
 lld/ELF/LinkerScript.h   |  7 +++++--
 3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 4593cc4..35f4df4 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -46,6 +46,10 @@ std::string lld::toString(const InputSectionBase *Sec) {
 }
 
 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::buildSectionOrder() {
     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);
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index b75802f..31fe3b9 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -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<InputSection *> V) {
   }
 }
 
-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::processSectionCommands() {
   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::processSectionCommands() {
     }
 
     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.
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 03c8392..1afb27c 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -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);
 
-- 
2.7.4