Reapply r110396, with fixes to appease the Linux buildbot gods.

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

diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index 27e1955ab284a7752790067d93ada23a4703b5c6..75282fae18bc531bc5a981faccdce66a6ddc311e 100644 (file)
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -1,10 +1,10 @@
 //===- ConstantMerge.cpp - Merge duplicate global constants ---------------===//
-// 
+//
 //                     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.
+//
 //===----------------------------------------------------------------------===//
 //
 // This file defines the interface to a pass that merges duplicate global
@@ -17,32 +17,42 @@
 //
 //===----------------------------------------------------------------------===//
 
+#define DEBUG_TYPE "constmerge"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/DerivedTypes.h"
 #include "llvm/Module.h"
 #include "llvm/Pass.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Statistic.h"
 using namespace llvm;
 
-namespace {
-  Statistic<> NumMerged("constmerge", "Number of global constants merged");
+STATISTIC(NumMerged, "Number of global constants merged");
 
+namespace {
   struct ConstantMerge : public ModulePass {
+    static char ID; // Pass identification, replacement for typeid
+    ConstantMerge() : ModulePass(ID) {}
+
     // 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;
+INITIALIZE_PASS(ConstantMerge, "constmerge",
+                "Merge Duplicate Global Constants", false, false);
+
 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.
+  DenseMap<Constant*, GlobalVariable*> CMap;
 
   // Replacements - This vector contains a list of replacements to perform.
-  std::vector<std::pair<GlobalVariable*, GlobalVariable*> > Replacements;
+  SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;
 
   bool MadeChange = false;
 
@@ -56,41 +66,50 @@ 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::giterator GV = M.gbegin(), E = M.gend(); GV != E; ++GV)
-      // 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);
-        
-        if (I == CMap.end()) {    // Nope, add it to the map
-          CMap.insert(I, std::make_pair(Init, 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()) {
-          // Make all uses of the duplicate constant use the canonical version.
-          Replacements.push_back(std::make_pair(I->second, GV));
-          I->second = GV;
-        }
+    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->hasLocalLinkage()) {
+        GV->eraseFromParent();
+        continue;
       }
-    
+      
+      // Only process constants with initializers in the default addres space.
+      if (!GV->isConstant() ||!GV->hasDefinitiveInitializer() ||
+          GV->getType()->getAddressSpace() != 0 || !GV->getSection().empty())
+        continue;
+      
+      Constant *Init = GV->getInitializer();
+
+      // Check to see if the initializer is already known.
+      GlobalVariable *&Slot = CMap[Init];
+
+      if (Slot == 0) {    // Nope, add it to the map.
+        Slot = GV;
+      } else if (GV->hasLocalLinkage()) {    // Yup, this is a duplicate!
+        // Make all uses of the duplicate constant use the canonical version.
+        Replacements.push_back(std::make_pair(GV, Slot));
+      }
+    }
+
     if (Replacements.empty())
       return MadeChange;
     CMap.clear();
-    
+
     // Now that we have figured out which replacements must be made, do them all
     // now.  This avoid invalidating the pointers in CMap, which are unneeded
     // now.
     for (unsigned i = 0, e = Replacements.size(); i != e; ++i) {
-      // Eliminate any uses of the dead global...
+      // Eliminate any uses of the dead global.
       Replacements[i].first->replaceAllUsesWith(Replacements[i].second);
-      
-      // Delete the global value from the module...
-      M.getGlobalList().erase(Replacements[i].first);
+
+      // Delete the global value from the module.
+      Replacements[i].first->eraseFromParent();
     }
-    
+
     NumMerged += Replacements.size();
     Replacements.clear();
   }