Remove the simplify-libcalls pass (finally)

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

diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index a21efced73b99c3cc50ffecfdfb282c6399b14d1..a7bf18896b52709acaab35c53a1fa80280e52483 100644 (file)
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -19,13 +19,16 @@
 
 #define DEBUG_TYPE "constmerge"
 #include "llvm/Transforms/IPO.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/Pass.h"
 using namespace llvm;
 
 STATISTIC(NumMerged, "Number of global constants merged");
@@ -37,10 +40,18 @@ namespace {
       initializeConstantMergePass(*PassRegistry::getPassRegistry());
     }
 
-    // run - For this pass, process all of the globals in the module,
-    // eliminating duplicate constants.
-    //
+    // For this pass, process all of the globals in the module, eliminating
+    // duplicate constants.
     bool runOnModule(Module &M);
+
+    // Return true iff we can determine the alignment of this global variable.
+    bool hasKnownAlignment(GlobalVariable *GV) const;
+
+    // Return the alignment of the global, including converting the default
+    // alignment to a concrete value.
+    unsigned getAlignment(GlobalVariable *GV) const;
+
+    const DataLayout *TD;
   };
 }
 
@@ -56,13 +67,13 @@ ModulePass *llvm::createConstantMergePass() { return new ConstantMerge(); }
 static void FindUsedValues(GlobalVariable *LLVMUsed,
                            SmallPtrSet<const GlobalValue*, 8> &UsedValues) {
   if (LLVMUsed == 0) return;
-  ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
-  if (Inits == 0) return;
-  
-  for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
-    if (GlobalValue *GV = 
-        dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
-      UsedValues.insert(GV);
+  ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
+
+  for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
+    Value *Operand = Inits->getOperand(i)->stripPointerCastsNoFollowAliases();
+    GlobalValue *GV = cast<GlobalValue>(Operand);
+    UsedValues.insert(GV);
+  }
 }
 
 // True if A is better than B.
@@ -77,15 +88,28 @@ static bool IsBetterCannonical(const GlobalVariable &A,
   return A.hasUnnamedAddr();
 }
 
+bool ConstantMerge::hasKnownAlignment(GlobalVariable *GV) const {
+  return TD || GV->getAlignment() != 0;
+}
+
+unsigned ConstantMerge::getAlignment(GlobalVariable *GV) const {
+  if (TD)
+    return TD->getPreferredAlignment(GV);
+  return GV->getAlignment();
+}
+
 bool ConstantMerge::runOnModule(Module &M) {
+  TD = getAnalysisIfAvailable<DataLayout>();
+
   // Find all the globals that are marked "used".  These cannot be merged.
   SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
   FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
   FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
   
-  // Map unique constant/section pairs to globals.  We don't want to merge
-  // globals in different sections.
-  DenseMap<Constant*, GlobalVariable*> CMap;
+  // Map unique <constants, has-unknown-alignment> pairs to globals.  We don't
+  // want to merge globals of unknown alignment with those of explicit
+  // alignment.  If we have DataLayout, we always know the alignment.
+  DenseMap<PointerIntPair<Constant*, 1, bool>, GlobalVariable*> CMap;
 
   // Replacements - This vector contains a list of replacements to perform.
   SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;
@@ -117,17 +141,24 @@ bool ConstantMerge::runOnModule(Module &M) {
           UsedGlobals.count(GV))
         continue;
 
+      // This transformation is legal for weak ODR globals in the sense it
+      // doesn't change semantics, but we really don't want to perform it
+      // anyway; it's likely to pessimize code generation, and some tools
+      // (like the Darwin linker in cases involving CFString) don't expect it.
+      if (GV->isWeakForLinker())
+        continue;
+
       Constant *Init = GV->getInitializer();
 
       // Check to see if the initializer is already known.
-      GlobalVariable *&Slot = CMap[Init];
+      PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
+      GlobalVariable *&Slot = CMap[Pair];
 
-      // If this is the first constant we find or if the old on is local,
-      // replace with the current one. It the current is externally visible
+      // If this is the first constant we find or if the old one is local,
+      // replace with the current one. If the current is externally visible
       // it cannot be replace, but can be the canonical constant we merge with.
-      if (Slot == 0 || IsBetterCannonical(*GV, *Slot)) {
+      if (Slot == 0 || IsBetterCannonical(*GV, *Slot))
         Slot = GV;
-      }
     }
 
     // Second: identify all globals that can be merged together, filling in
@@ -152,7 +183,8 @@ bool ConstantMerge::runOnModule(Module &M) {
       Constant *Init = GV->getInitializer();
 
       // Check to see if the initializer is already known.
-      GlobalVariable *Slot = CMap[Init];
+      PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
+      GlobalVariable *Slot = CMap[Pair];
 
       if (!Slot || Slot == GV)
         continue;
@@ -175,6 +207,14 @@ bool ConstantMerge::runOnModule(Module &M) {
     // now.  This avoid invalidating the pointers in CMap, which are unneeded
     // now.
     for (unsigned i = 0, e = Replacements.size(); i != e; ++i) {
+      // Bump the alignment if necessary.
+      if (Replacements[i].first->getAlignment() ||
+          Replacements[i].second->getAlignment()) {
+        Replacements[i].second->setAlignment(std::max(
+            Replacements[i].first->getAlignment(),
+            Replacements[i].second->getAlignment()));
+      }
+
       // Eliminate any uses of the dead global.
       Replacements[i].first->replaceAllUsesWith(Replacements[i].second);