bug 122:

- Move these functions from other places
- Provide implementations of Constant class overrides in GlobalValue

llvm-svn: 14936

llvm/lib/VMCore/Globals.cpp

@@ -0,0 +1,139 @@
+//===-- Globals.cpp - Implement the Global object classes -----------------===//
+// 
+//                     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 implements the GlobalValue & GlobalVariable classes for the VMCore
+// library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DerivedTypes.h"
+#include "llvm/GlobalVariable.h"
+#include "llvm/Module.h"
+#include "llvm/SymbolTable.h"
+#include "Support/LeakDetector.h"
+
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+//                            GlobalValue Class
+//===----------------------------------------------------------------------===//
+
+/// This could be named "SafeToDestroyGlobalValue". It just makes sure that 
+/// there are no non-constant uses of this GlobalValue. If there aren't then
+/// this and the transitive closure of the constants can be deleted. See the
+/// destructor for details.
+namespace {
+bool removeDeadConstantUsers(Constant* C) {
+  while (!C->use_empty()) {
+    if (Constant *User = dyn_cast<Constant>(C->use_back())) {
+      if (!removeDeadConstantUsers(User)) 
+        return false; // Constant wasn't dead
+    } else {
+      return false; // Non-constant usage;
+    }
+  }
+  if (!isa<GlobalValue>(C))
+    C->destroyConstant();
+  return true;
+}
+}
+
+/// removeDeadConstantUsers - If there are any dead constant users dangling
+/// off of this global value, remove them.  This method is useful for clients
+/// that want to check to see if a global is unused, but don't want to deal
+/// with potentially dead constants hanging off of the globals.
+///
+/// This function returns true if the global value is now dead.  If all 
+/// users of this global are not dead, this method may return false and
+/// leave some of them around.
+bool GlobalValue::removeDeadConstantUsers() {
+  while(!use_empty()) {
+    if (Constant* User = dyn_cast<Constant>(use_back())) {
+      if (!::removeDeadConstantUsers(User))
+        return false; // Constant wasn't dead
+    } else {
+      return false; // Non-constant usage;
+    }
+  }
+  return true;
+}
+
+/// This virtual destructor is responsible for deleting any transitively dead
+/// Constants that are using the GlobalValue.
+GlobalValue::~GlobalValue() {
+  // Its an error to attempt destruction with non-constant uses remaining.
+  bool okay_to_destruct = removeDeadConstantUsers();
+  assert(okay_to_destruct && 
+         "Can't destroy GlobalValue with non-constant uses.");
+}
+
+/// Override destroyConstant to make sure it doesn't get called on 
+/// GlobalValue's because they shouldn't be treated like other constants.
+void GlobalValue::destroyConstant() {
+  assert(0 && "You can't GV->destroyConstant()!");
+  abort();
+}
+//===----------------------------------------------------------------------===//
+// GlobalVariable Implementation
+//===----------------------------------------------------------------------===//
+
+GlobalVariable::GlobalVariable(const Type *Ty, bool constant, LinkageTypes Link,
+                               Constant *Initializer,
+                               const std::string &Name, Module *ParentModule)
+  : GlobalValue(PointerType::get(Ty), Value::GlobalVariableVal, Link, Name),
+    isConstantGlobal(constant) {
+  if (Initializer) Operands.push_back(Use((Value*)Initializer, this));
+
+  LeakDetector::addGarbageObject(this);
+
+  if (ParentModule)
+    ParentModule->getGlobalList().push_back(this);
+}
+
+void GlobalVariable::setParent(Module *parent) {
+  if (getParent())
+    LeakDetector::addGarbageObject(this);
+  Parent = parent;
+  if (getParent())
+    LeakDetector::removeGarbageObject(this);
+}
+
+// Specialize setName to take care of symbol table majik
+void GlobalVariable::setName(const std::string &name, SymbolTable *ST) {
+  Module *P;
+  assert((ST == 0 || (!getParent() || ST == &getParent()->getSymbolTable())) &&
+         "Invalid symtab argument!");
+  if ((P = getParent()) && hasName()) P->getSymbolTable().remove(this);
+  Value::setName(name);
+  if (P && hasName()) P->getSymbolTable().insert(this);
+}
+
+void GlobalVariable::replaceUsesOfWithOnConstant(Value *From, Value *To,
+                                                 bool DisableChecking )
+{
+  // If you call this, then you better know this GVar has a constant
+  // initializer worth replacing. Enforce that here.
+  assert(getNumOperands() == 1 && 
+         "Attempt to replace uses of Constants on a GVar with no initializer");
+
+  // And, since you know it has an initializer, the From value better be
+  // the initializer :)
+  assert(getOperand(0) == From &&
+         "Attempt to replace wrong constant initializer in GVar");
+
+  // And, you better have a constant for the replacement value
+  assert(isa<Constant>(To) &&
+         "Attempt to replace GVar initializer with non-constant");
+  
+  // Okay, preconditions out of the way, replace the constant initializer.
+  this->setOperand(0,To);
+}
+
+// vim: sw=2 ai
+