From 8a32784ad4a2110c4c73189c3314289c407a6183 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 14 Jul 2004 21:44:00 +0000
Subject: [PATCH] * Fairly substantial change.  Instead of creating new
 globalvariables, then   replaceAllUsesWith'ing any forward references, just
 use the forward   reference if it exists.

This introduces GetForwardRefForGlobal, which will eventually completely
replace the horrible DeclareNewGlobalValue function.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@14828 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AsmParser/llvmAsmParser.y | 63 +++++++++++++++++++++++++++--------
 1 file changed, 49 insertions(+), 14 deletions(-)

diff --git a/lib/AsmParser/llvmAsmParser.y b/lib/AsmParser/llvmAsmParser.y
index 2521a4bb270..b2ac21eed9b 100644
--- a/lib/AsmParser/llvmAsmParser.y
+++ b/lib/AsmParser/llvmAsmParser.y
@@ -112,6 +112,21 @@ static struct PerModuleInfo {
   }
 
 
+  // GetForwardRefForGlobal - Check to see if there is a forward reference
+  // for this global.  If so, remove it from the GlobalRefs map and return it.
+  // If not, just return null.
+  GlobalValue *GetForwardRefForGlobal(const PointerType *PTy, ValID ID) {
+    // Check to see if there is a forward reference to this global variable...
+    // if there is, eliminate it and patch the reference to use the new def'n.
+    GlobalRefsType::iterator I = GlobalRefs.find(std::make_pair(PTy, ID));
+    GlobalValue *Ret = 0;
+    if (I != GlobalRefs.end()) {
+      Ret = I->second;
+      GlobalRefs.erase(I);
+    }
+    return Ret;
+  }
+
   // DeclareNewGlobalValue - Called every time a new GV has been defined.  This
   // is used to remove things from the forward declaration map, resolving them
   // to the correct thing as needed.
@@ -626,15 +641,30 @@ static void ParseGlobalVariable(char *NameStr,GlobalValue::LinkageTypes Linkage,
     }
   }
 
-  GlobalVariable *GV = new GlobalVariable(Ty, isConstantGlobal, Linkage,
-                                          Initializer, Name, 
-                                          CurModule.CurrentModule);
-  int Slot = InsertValue(GV, CurModule.Values);
-  
-  if (Slot != -1) {
-    CurModule.DeclareNewGlobalValue(GV, ValID::create(Slot));
+  const PointerType *PTy = PointerType::get(Ty); 
+
+  // See if this global value was forward referenced.  If so, recycle the
+  // object.
+  ValID ID; 
+  if (!Name.empty()) {
+    ID = ValID::create((char*)Name.c_str());
   } else {
-    CurModule.DeclareNewGlobalValue(GV, ValID::create((char*)Name.c_str()));
+    ID = ValID::create((int)CurModule.Values[PTy].size());
+  }
+
+  if (GlobalValue *FWGV = CurModule.GetForwardRefForGlobal(PTy, ID)) {
+    // Move the global to the end of the list, from whereever it was 
+    // previously inserted.
+    GlobalVariable *GV = cast<GlobalVariable>(FWGV);
+    CurModule.CurrentModule->getGlobalList().remove(GV);
+    CurModule.CurrentModule->getGlobalList().push_back(GV);
+    GV->setInitializer(Initializer);
+    GV->setLinkage(Linkage);
+    GV->setConstant(isConstantGlobal);
+  } else {
+    // Otherwise there is no existing GV to use, create one now.
+    new GlobalVariable(Ty, isConstantGlobal, Linkage, Initializer, Name, 
+                       CurModule.CurrentModule);
   }
 }
 
@@ -1261,15 +1291,20 @@ ConstVal: Types '[' ConstVector ']' { // Nonempty unsized arr
 	V = I->second;             // Placeholder already exists, use it...
         $2.destroy();
       } else {
+        std::string Name;
+
+        /// FIXME: We shouldn't be creating global vars as forward refs for
+        /// functions at all here!
+        if (!isa<FunctionType>(PT->getElementType()))
+          if ($2.Type == ValID::NameVal) Name = $2.Name;
+
 	// Create a placeholder for the global variable reference...
-	GlobalVariable *GV = new GlobalVariable(PT->getElementType(),
-                                                false,
-                                                GlobalValue::ExternalLinkage);
+	GlobalVariable *GV = new GlobalVariable(PT->getElementType(), false,
+                                                GlobalValue::ExternalLinkage,0,
+                                                Name, CurModule.CurrentModule);
+
 	// Keep track of the fact that we have a forward ref to recycle it
 	CurModule.GlobalRefs.insert(std::make_pair(std::make_pair(PT, $2), GV));
-
-	// Must temporarily push this value into the module table...
-	CurModule.CurrentModule->getGlobalList().push_back(GV);
 	V = GV;
       }
     }