Extend Module::getOrInsertGlobal to control the construction of the

GlobalVariable

Summary:
Extend Module::getOrInsertGlobal to accept a callback for creating a new
GlobalVariable if necessary instead of calling the GV constructor
directly using default arguments. Additionally overload
getOrInsertGlobal for the previous default behavior.

Reviewers: chandlerc

Subscribers: hiraditya, llvm-commits, bollu

Differential Revision: https://reviews.llvm.org/D56130

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350219 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Module.h

@@ -403,11 +403,15 @@ class Module {
   }
 
   /// Look up the specified global in the module symbol table.
-  ///   1. If it does not exist, add a declaration of the global and return it.
-  ///   2. Else, the global exists but has the wrong type: return the function
-  ///      with a constantexpr cast to the right type.
-  ///   3. Finally, if the existing global is the correct declaration, return
-  ///      the existing global.
+  /// If it does not exist, invoke a callback to create a declaration of the
+  /// global and return it. The global is constantexpr casted to the expected
+  /// type if necessary.
+  Constant *
+  getOrInsertGlobal(StringRef Name, Type *Ty,
+                    function_ref<GlobalVariable *()> CreateGlobalCallback);
+
+  /// Look up the specified global in the module symbol table. If required, this
+  /// overload constructs the global variable using its constructor's defaults.
   Constant *getOrInsertGlobal(StringRef Name, Type *Ty);
 
 /// @}

lib/IR/Module.cpp

@@ -203,16 +203,14 @@ GlobalVariable *Module::getGlobalVariable(StringRef Name,
 ///      with a constantexpr cast to the right type.
 ///   3. Finally, if the existing global is the correct declaration, return the
 ///      existing global.
-Constant *Module::getOrInsertGlobal(StringRef Name, Type *Ty) {
+Constant *Module::getOrInsertGlobal(
+    StringRef Name, Type *Ty,
+    function_ref<GlobalVariable *()> CreateGlobalCallback) {
   // See if we have a definition for the specified global already.
   GlobalVariable *GV = dyn_cast_or_null<GlobalVariable>(getNamedValue(Name));
-  if (!GV) {
-    // Nope, add it
-    GlobalVariable *New =
-      new GlobalVariable(*this, Ty, false, GlobalVariable::ExternalLinkage,
-                         nullptr, Name);
-     return New;                    // Return the new declaration.
-  }
+  if (!GV)
+    GV = CreateGlobalCallback();
+  assert(GV && "The CreateGlobalCallback is expected to create a global");
 
   // If the variable exists but has the wrong type, return a bitcast to the
   // right type.
@@ -225,6 +223,14 @@ Constant *Module::getOrInsertGlobal(StringRef Name, Type *Ty) {
   return GV;
 }
 
+// Overload to construct a global variable using its constructor's defaults.
+Constant *Module::getOrInsertGlobal(StringRef Name, Type *Ty) {
+  return getOrInsertGlobal(Name, Ty, [&] {
+    return new GlobalVariable(*this, Ty, false, GlobalVariable::ExternalLinkage,
+                              nullptr, Name);
+  });
+}
+
 //===----------------------------------------------------------------------===//
 // Methods for easy access to the global variables in the module.
 //