From c67ebfa78810f518c54381ed38c09d3a0afd77e4 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 9 Oct 2002 23:16:04 +0000
Subject: [PATCH]   - Dramatically simplify the ConstantMerge code now that    
 Value::replaceAllUsesWith works with constants correctly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4104 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/ConstantMerge.cpp | 105 +--------------------------
 1 file changed, 3 insertions(+), 102 deletions(-)

diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index 02a9100a2e7..a73fca2b3c5 100644
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -12,23 +12,19 @@
 
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Module.h"
-#include "llvm/Constants.h"
 #include "llvm/Pass.h"
 #include "Support/Statistic.h"
 
 namespace {
+  Statistic<> NumMerged("constmerge", "Number of global constants merged");
+
   struct ConstantMerge : public Pass {
     // run - For this pass, process all of the globals in the module,
     // eliminating duplicate constants.
     //
     bool run(Module &M);
-
-  private:
-    void replaceUsesOfWith(GlobalVariable *Old, GlobalVariable *New);
-    void replaceConstantWith(Constant *Old, Constant *New);
   };
 
-  Statistic<> NumMerged("constmerge", "Number of global constants merged");
   RegisterOpt<ConstantMerge> X("constmerge","Merge Duplicate Global Constants");
 }
 
@@ -51,7 +47,7 @@ bool ConstantMerge::run(Module &M) {
         CMap.insert(I, std::make_pair(Init, GV));
       } else {                  // Yup, this is a duplicate!
         // Make all uses of the duplicate constant use the cannonical version...
-        replaceUsesOfWith(GV, I->second);
+        GV->replaceAllUsesWith(I->second);
 
         // Delete the global value from the module... and back up iterator to
         // not skip the next global...
@@ -64,98 +60,3 @@ bool ConstantMerge::run(Module &M) {
 
   return MadeChanges;
 }
-
-/// replaceUsesOfWith - Replace all uses of Old with New.  For instructions,
-/// this is a really simple matter of replacing the reference to Old with a
-/// reference to New.  For constants references, however, we must carefully
-/// build replacement constants to substitute in.
-///
-void ConstantMerge::replaceUsesOfWith(GlobalVariable *Old, GlobalVariable *New){
-  while (!Old->use_empty()) {
-    User *U = Old->use_back();
-    if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(U))
-      replaceConstantWith(CPR, ConstantPointerRef::get(New));
-    else
-      U->replaceUsesOfWith(Old, New);
-  }
-}
-
-/// replaceWith - Ok, so we have a constant 'Old' and we want to replace it with
-/// 'New'.  To do this, we have to recursively go through the uses of Old,
-/// replacing them with new things.  The problem is that if a constant uses Old,
-/// then we need to replace the uses of the constant with uses of the equivalent
-/// constant that uses New instead.
-///
-void ConstantMerge::replaceConstantWith(Constant *Old, Constant *New) {
-  while (!Old->use_empty()) {
-    User *U = Old->use_back();
-
-    if (Constant *C = dyn_cast<Constant>(U)) {
-      Constant *Replacement = 0;
-      
-      // Depending on the type of constant, build a suitable replacement...
-      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
-        if (CE->getOpcode() == Instruction::GetElementPtr) {
-          std::vector<Constant*> Indices;
-          Constant *Pointer = cast<Constant>(CE->getOperand(0));
-          Indices.reserve(CE->getNumOperands()-1);
-          if (Pointer == Old) Pointer = New;
-
-          for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) {
-            Constant *Val = cast<Constant>(CE->getOperand(i));
-            if (Val == Old) Val = New;
-            Indices.push_back(Val);
-          }
-          Replacement = ConstantExpr::getGetElementPtr(Pointer, Indices);
-        } else if (CE->getOpcode() == Instruction::Cast) {
-          assert(CE->getOperand(0) == Old && "Cast only has one use!");
-          Replacement = ConstantExpr::getCast(New, CE->getType());
-        } else if (CE->getNumOperands() == 2) {
-          Constant *C1 = cast<Constant>(CE->getOperand(0));
-          Constant *C2 = cast<Constant>(CE->getOperand(1));
-          if (C1 == Old) C1 = New;
-          if (C2 == Old) C2 = New;
-          Replacement = ConstantExpr::get(CE->getOpcode(), C1, C2);
-        } else {
-          assert(0 && "Unknown ConstantExpr type!");
-        }
-
-
-      } else if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
-        std::vector<Constant*> Values;
-        Values.reserve(CA->getValues().size());
-        for (unsigned i = 0, e = CA->getValues().size(); i != e; ++i) {
-          Constant *Val = cast<Constant>(CA->getValues()[i]);
-          if (Val == Old) Val = New;
-          Values.push_back(Val);
-        }
-
-        Replacement = ConstantArray::get(CA->getType(), Values);
-      } else if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
-        std::vector<Constant*> Values;
-        Values.reserve(CS->getValues().size());
-
-        for (unsigned i = 0, e = CS->getValues().size(); i != e; ++i) {
-          Constant *Val = cast<Constant>(CS->getValues()[i]);
-          if (Val == Old) Val = New;
-          Values.push_back(Val);
-        }
-
-        Replacement = ConstantStruct::get(CS->getType(), Values);
-      } else {
-        assert(0 && "Unexpected/unknown constant type!");
-      }
-      
-      // Now that we have a suitable replacement, recursively eliminate C.
-      replaceConstantWith(C, Replacement);
-
-    } else {
-      // If it is not a constant, we can simply replace uses of Old with New.
-      U->replaceUsesOfWith(Old, New);
-    }
-
-  }
-
-  // No-one refers to this old dead constant now, destroy it!
-  Old->destroyConstant();
-}