Remove attribution from file headers, per discussion on llvmdev.

[oota-llvm.git] / lib / Transforms / IPO / ConstantMerge.cpp

diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index b6026f273640ed0dfff620f8dda32849bf4a0825..7c71065674ec798a538f6f75de871a0d91cff503 100644 (file)
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -2,8 +2,8 @@
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
@@ -17,29 +17,37 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define DEBUG_TYPE "constmerge"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
 using namespace llvm;
 
+STATISTIC(NumMerged, "Number of global constants merged");
+
 namespace {
-  Statistic<> NumMerged("constmerge", "Number of global constants merged");
+  struct VISIBILITY_HIDDEN ConstantMerge : public ModulePass {
+    static char ID; // Pass identification, replacement for typeid
+    ConstantMerge() : ModulePass((intptr_t)&ID) {}
 
-  struct ConstantMerge : public ModulePass {
     // run - For this pass, process all of the globals in the module,
     // eliminating duplicate constants.
     //
     bool runOnModule(Module &M);
   };
 
-  RegisterOpt<ConstantMerge> X("constmerge","Merge Duplicate Global Constants");
+  char ConstantMerge::ID = 0;
+  RegisterPass<ConstantMerge>X("constmerge","Merge Duplicate Global Constants");
 }
 
 ModulePass *llvm::createConstantMergePass() { return new ConstantMerge(); }
 
 bool ConstantMerge::runOnModule(Module &M) {
-  std::map<Constant*, GlobalVariable*> CMap;
+  // Map unique constant/section pairs to globals.  We don't want to merge
+  // globals in different sections.
+  std::map<std::pair<Constant*, std::string>, GlobalVariable*> CMap;
 
   // Replacements - This vector contains a list of replacements to perform.
   std::vector<std::pair<GlobalVariable*, GlobalVariable*> > Replacements;
@@ -56,25 +64,36 @@ bool ConstantMerge::runOnModule(Module &M) {
     // because doing so may cause initializers of other globals to be rewritten,
     // invalidating the Constant* pointers in CMap.
     //
-    for (Module::global_iterator GV = M.global_begin(), E = M.global_end(); GV != E; ++GV)
-      // Only process constants with initializers
+    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
+         GVI != E; ) {
+      GlobalVariable *GV = GVI++;
+      
+      // If this GV is dead, remove it.
+      GV->removeDeadConstantUsers();
+      if (GV->use_empty() && GV->hasInternalLinkage()) {
+        GV->eraseFromParent();
+        continue;
+      }
+      
+      // Only process constants with initializers.
       if (GV->isConstant() && GV->hasInitializer()) {
         Constant *Init = GV->getInitializer();
 
-        // Check to see if the initializer is already known...
-        std::map<Constant*, GlobalVariable*>::iterator I = CMap.find(Init);
+        // Check to see if the initializer is already known.
+        GlobalVariable *&Slot = CMap[std::make_pair(Init, GV->getSection())];
 
-        if (I == CMap.end()) {    // Nope, add it to the map
-          CMap.insert(I, std::make_pair(Init, GV));
+        if (Slot == 0) {    // Nope, add it to the map.
+          Slot = GV;
         } else if (GV->hasInternalLinkage()) {    // Yup, this is a duplicate!
           // Make all uses of the duplicate constant use the canonical version.
-          Replacements.push_back(std::make_pair(GV, I->second));
-        } else if (I->second->hasInternalLinkage()) {
+          Replacements.push_back(std::make_pair(GV, Slot));
+        } else if (GV->hasInternalLinkage()) {
           // Make all uses of the duplicate constant use the canonical version.
-          Replacements.push_back(std::make_pair(I->second, GV));
-          I->second = GV;
+          Replacements.push_back(std::make_pair(Slot, GV));
+          Slot = GV;
         }
       }
+    }
 
     if (Replacements.empty())
       return MadeChange;