[Autobackout][FuncReg]Revert of change: 89fc074

Partial revert to remove changes that adds external global variables to the symbol table.

Change-Id: I01d80ac9903e96bf962ef00f4586e130a713f9ec

Author: dlei6g

IGC/Compiler/CISACodeGen/CISABuilder.cpp

@@ -4632,18 +4632,26 @@ namespace IGC
         for (auto global : modMD->inlineProgramScopeOffsets)
         {
             GlobalVariable* pGlobal = global.first;
-            bool needRelocation = false;
-            for (auto ui = pGlobal->user_begin(), ue = pGlobal->user_end(); ui != ue; ui++)
+
+            // Create symbol for external globals
+            bool needSymbol = (pGlobal->getLinkage() == GlobalValue::ExternalLinkage) || (pGlobal->getLinkage() == GlobalValue::CommonLinkage);
+            if (!needSymbol)
             {
-                // Check if need relocation
-                Instruction* inst = dyn_cast<Instruction>(*ui);
-                if (inst && inst->getParent()->getParent()->hasFnAttribute("EnableGlobalRelocation"))
+                pGlobal->removeDeadConstantUsers();
+                // Also need to create symbol if it requires relocation
+                for (auto ui = pGlobal->user_begin(), ue = pGlobal->user_end(); ui != ue; ui++)
                 {
-                    needRelocation = true;
-                    break;
+                    // Check if need relocation
+                    Instruction* inst = dyn_cast<Instruction>(*ui);
+                    if (inst && inst->getParent()->getParent()->hasFnAttribute("EnableGlobalRelocation"))
+                    {
+                        needSymbol = true;
+                        break;
+                    }
                 }
             }
-            if (needRelocation)
+
+            if (needSymbol)
             {
                 StringRef name = pGlobal->getName();
                 unsigned addrSpace = pGlobal->getType()->getAddressSpace();

IGC/Compiler/Optimizer/OpenCLPasses/ProgramScopeConstants/ProgramScopeConstantAnalysis.cpp

@@ -110,8 +110,10 @@ bool ProgramScopeConstantAnalysis::runOnModule(Module& M)
             continue;
         }
 
-        // If this variable isn't used, don't add it to the buffer.
-        if (globalVar->use_empty())
+        // If this variable isn't used and not exposed externally, don't add it to the buffer.
+        if (globalVar->use_empty() &&
+            globalVar->getLinkage() != GlobalValue::CommonLinkage &&
+            globalVar->getLinkage() != GlobalValue::ExternalLinkage)
         {
             continue;
         }