From 5dc47ff03975b9adde9dd833db2b646eb4295710 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 12 Aug 2009 23:55:02 +0000
Subject: [PATCH] implement support for uniquing MachO sections.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78866 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../llvm/Target/TargetLoweringObjectFile.h    | 25 +++++++++----
 lib/Target/TargetLoweringObjectFile.cpp       | 37 +++++++++++++++----
 2 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/include/llvm/Target/TargetLoweringObjectFile.h b/include/llvm/Target/TargetLoweringObjectFile.h
index b6710821ed2..cbb585e131b 100644
--- a/include/llvm/Target/TargetLoweringObjectFile.h
+++ b/include/llvm/Target/TargetLoweringObjectFile.h
@@ -20,6 +20,7 @@
 namespace llvm {
   class Mangler;
   class MCSection;
+  class MCSectionMachO;
   class MCContext;
   class GlobalValue;
   class StringRef;
@@ -28,6 +29,9 @@ namespace llvm {
   
 class TargetLoweringObjectFile {
   MCContext *Ctx;
+  
+  TargetLoweringObjectFile(const TargetLoweringObjectFile&); // DO NOT IMPLEMENT
+  void operator=(const TargetLoweringObjectFile&);           // DO NOT IMPLEMENT
 protected:
   
   TargetLoweringObjectFile();
@@ -225,6 +229,8 @@ public:
   
   
 class TargetLoweringObjectFileMachO : public TargetLoweringObjectFile {
+  mutable void *UniquingMap;
+  
   const MCSection *CStringSection;
   const MCSection *UStringSection;
   const MCSection *TextCoalSection;
@@ -236,6 +242,8 @@ class TargetLoweringObjectFileMachO : public TargetLoweringObjectFile {
   const MCSection *EightByteConstantSection;
   const MCSection *SixteenByteConstantSection;
 public:
+  TargetLoweringObjectFileMachO() : UniquingMap(0) {}
+  ~TargetLoweringObjectFileMachO();
   
   virtual void Initialize(MCContext &Ctx, const TargetMachine &TM);
 
@@ -257,16 +265,17 @@ public:
 
   /// getMachOSection - Return the MCSection for the specified mach-o section.
   /// This requires the operands to be valid.
-  const MCSection *getMachOSection(const StringRef &Segment,
-                                   const StringRef &Section,
-                                   unsigned TypeAndAttributes,
-                                   SectionKind K) const {
+  const MCSectionMachO *getMachOSection(const StringRef &Segment,
+                                        const StringRef &Section,
+                                        unsigned TypeAndAttributes,
+                                        SectionKind K) const {
     return getMachOSection(Segment, Section, TypeAndAttributes, 0, K);
   }
-  const MCSection *getMachOSection(const StringRef &Segment,
-                                   const StringRef &Section,
-                                   unsigned TypeAndAttributes,
-                                   unsigned Reserved2, SectionKind K) const;
+  const MCSectionMachO *getMachOSection(const StringRef &Segment,
+                                        const StringRef &Section,
+                                        unsigned TypeAndAttributes,
+                                        unsigned Reserved2,
+                                        SectionKind K) const;
 
   /// getTextCoalSection - Return the "__TEXT,__textcoal_nt" section we put weak
   /// symbols into.
diff --git a/lib/Target/TargetLoweringObjectFile.cpp b/lib/Target/TargetLoweringObjectFile.cpp
index 321af98a74b..904f01ae354 100644
--- a/lib/Target/TargetLoweringObjectFile.cpp
+++ b/lib/Target/TargetLoweringObjectFile.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/Mangler.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 using namespace llvm;
 
@@ -128,7 +129,6 @@ SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV,
   const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
   if (GVar == 0)
     return SectionKind::getText();
-
   
   // Handle thread-local data first.
   if (GVar->isThreadLocal()) {
@@ -509,17 +509,40 @@ getSectionForConstant(SectionKind Kind) const {
 //                                 MachO
 //===----------------------------------------------------------------------===//
 
+typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
 
-const MCSection *TargetLoweringObjectFileMachO::
+TargetLoweringObjectFileMachO::~TargetLoweringObjectFileMachO() {
+  // If we have the MachO uniquing map, free it.
+  delete (MachOUniqueMapTy*)UniquingMap;
+}
+
+
+const MCSectionMachO *TargetLoweringObjectFileMachO::
 getMachOSection(const StringRef &Segment, const StringRef &Section,
                 unsigned TypeAndAttributes,
                 unsigned Reserved2, SectionKind Kind) const {
-  // FIXME: UNIQUE HERE.
-  //if (MCSection *S = getContext().GetSection(Name))
-  //  return S;
+  // We unique sections by their segment/section pair.  The returned section
+  // may not have the same flags as the requested section, if so this should be
+  // diagnosed by the client as an error.
   
-  return MCSectionMachO::Create(Segment, Section, TypeAndAttributes, Reserved2,
-                                Kind, getContext());
+  // Create the map if it doesn't already exist.
+  if (UniquingMap == 0)
+    UniquingMap = new MachOUniqueMapTy();
+  MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)UniquingMap;
+  
+  // Form the name to look up.
+  SmallString<64> Name;
+  Name.append(Segment.begin(), Segment.end());
+  Name.push_back(',');
+  Name.append(Section.begin(), Section.end());
+  
+  // Do the lookup, if we have a hit, return it.
+  const MCSectionMachO *&Entry = Map[StringRef(Name.data(), Name.size())];
+  if (Entry) return Entry;
+
+  // Otherwise, return a new section.
+  return Entry = MCSectionMachO::Create(Segment, Section, TypeAndAttributes,
+                                        Reserved2, Kind, getContext());
 }