From 8f7565b6f233fa9b66e1721533c7a97001abdf44 Mon Sep 17 00:00:00 2001
From: Peter Smith <peter.smith@linaro.org>
Date: Tue, 6 Jun 2017 09:42:44 +0000
Subject: [PATCH] [ELF] Refactor ThunkCreator to not key on OutputSection for
 Thunks

In preparation for inserting Thunks into InputSectionDescriptions this
simple change associates added Thunks with a vector of InputSections instead
of an OutputSection. As of now we are just using OutputSection::Sections.

Differential Revision: https://reviews.llvm.org/D33832

llvm-svn: 304782
---
 lld/ELF/Relocations.cpp | 64 ++++++++++++++++++++++-------------------
 lld/ELF/Relocations.h   |  5 ++--
 2 files changed, 37 insertions(+), 32 deletions(-)

diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 54cc6dd89d46..bbbc706ff40c 100644
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -967,33 +967,38 @@ template <class ELFT> void elf::scanRelocations(InputSectionBase &S) {
 // in the Sections vector, and recalculate the InputSection output section
 // offsets.
 // This may invalidate any output section offsets stored outside of InputSection
-void ThunkCreator::mergeThunks(OutputSection *OS,
-                               std::vector<ThunkSection *> &Thunks) {
-  // Order Thunks in ascending OutSecOff
-  auto ThunkCmp = [](const ThunkSection *A, const ThunkSection *B) {
-    return A->OutSecOff < B->OutSecOff;
-  };
-  std::stable_sort(Thunks.begin(), Thunks.end(), ThunkCmp);
+void ThunkCreator::mergeThunks() {
+  for (auto &KV : ThunkSections) {
+    std::vector<InputSection *> *ISR = KV.first;
+    std::vector<ThunkSection *> &Thunks = KV.second;
 
-  // Merge sorted vectors of Thunks and InputSections by OutSecOff
-  std::vector<InputSection *> Tmp;
-  Tmp.reserve(OS->Sections.size() + Thunks.size());
-  auto MergeCmp = [](const InputSection *A, const InputSection *B) {
-    // std::merge requires a strict weak ordering.
-    if (A->OutSecOff < B->OutSecOff)
-      return true;
-    if (A->OutSecOff == B->OutSecOff)
-      // Check if Thunk is immediately before any specific Target InputSection
-      // for example Mips LA25 Thunks.
-      if (auto *TA = dyn_cast<ThunkSection>(A))
-        if (TA && TA->getTargetInputSection() == B)
-          return true;
-    return false;
-  };
-  std::merge(OS->Sections.begin(), OS->Sections.end(), Thunks.begin(),
-             Thunks.end(), std::back_inserter(Tmp), MergeCmp);
-  OS->Sections = std::move(Tmp);
-  OS->assignOffsets();
+    // Order Thunks in ascending OutSecOff
+    auto ThunkCmp = [](const ThunkSection *A, const ThunkSection *B) {
+      return A->OutSecOff < B->OutSecOff;
+    };
+    std::stable_sort(Thunks.begin(), Thunks.end(), ThunkCmp);
+
+    // Merge sorted vectors of Thunks and InputSections by OutSecOff
+    std::vector<InputSection *> Tmp;
+    Tmp.reserve(ISR->size() + Thunks.size());
+    auto MergeCmp = [](const InputSection *A, const InputSection *B) {
+      // std::merge requires a strict weak ordering.
+      if (A->OutSecOff < B->OutSecOff)
+        return true;
+      if (A->OutSecOff == B->OutSecOff)
+        // Check if Thunk is immediately before any specific Target InputSection
+        // for example Mips LA25 Thunks.
+        if (auto *TA = dyn_cast<ThunkSection>(A))
+          if (TA && TA->getTargetInputSection() == B)
+            return true;
+      return false;
+    };
+    std::merge(ISR->begin(), ISR->end(), Thunks.begin(), Thunks.end(),
+               std::back_inserter(Tmp), MergeCmp);
+    OutputSection *OS = Thunks.front()->getParent();
+    OS->Sections = std::move(Tmp);
+    OS->assignOffsets();
+  }
 }
 
 ThunkSection *ThunkCreator::getOSThunkSec(ThunkSection *&TS,
@@ -1006,7 +1011,7 @@ ThunkSection *ThunkCreator::getOSThunkSec(ThunkSection *&TS,
         break;
     }
     TS = make<ThunkSection>(OS, Off);
-    ThunkSections[OS].push_back(TS);
+    ThunkSections[&OS->Sections].push_back(TS);
   }
   return TS;
 }
@@ -1017,7 +1022,7 @@ ThunkSection *ThunkCreator::getISThunkSec(InputSection *IS, OutputSection *OS) {
     return TS;
   auto *TOS = IS->getParent();
   TS = make<ThunkSection>(TOS, IS->OutSecOff);
-  ThunkSections[TOS].push_back(TS);
+  ThunkSections[&TOS->Sections].push_back(TS);
   ThunkedSections[IS] = TS;
   return TS;
 }
@@ -1074,8 +1079,7 @@ bool ThunkCreator::createThunks(ArrayRef<OutputSection *> OutputSections) {
   }
 
   // Merge all created synthetic ThunkSections back into OutputSection
-  for (auto &KV : ThunkSections)
-    mergeThunks(KV.first, KV.second);
+  mergeThunks();
   return !ThunkSections.empty();
 }
 
diff --git a/lld/ELF/Relocations.h b/lld/ELF/Relocations.h
index 206f0d9423c9..44b356a258d1 100644
--- a/lld/ELF/Relocations.h
+++ b/lld/ELF/Relocations.h
@@ -126,7 +126,7 @@ public:
   bool createThunks(ArrayRef<OutputSection *> OutputSections);
 
 private:
-  void mergeThunks(OutputSection *OS, std::vector<ThunkSection *> &Thunks);
+  void mergeThunks();
   ThunkSection *getOSThunkSec(ThunkSection *&TS, OutputSection *OS);
   ThunkSection *getISThunkSec(InputSection *IS, OutputSection *OS);
   std::pair<Thunk *, bool> getThunk(SymbolBody &Body, uint32_t Type);
@@ -138,7 +138,8 @@ private:
   llvm::DenseMap<InputSection *, ThunkSection *> ThunkedSections;
 
   // Track the ThunksSections that need to be inserted into an OutputSection
-  std::map<OutputSection *, std::vector<ThunkSection *>> ThunkSections;
+  std::map<std::vector<InputSection *> *, std::vector<ThunkSection *>>
+      ThunkSections;
 };
 
 // Return a int64_t to make sure we get the sign extension out of the way as