Revert ef7544a: "Enabling uninitialized external global variables."

This reverts commit ef7544a967bb61d1770eabd92c48aa8e9e9438f4.

This change enables external global varibles for compute workloads,
including variables without initializers. External variables without
initializers will be emitted as UNDEF symbols in zebin ELF binary.

Author: mbelicki

IGC/AdaptorOCL/OCL/sp/zebin_builder.cpp

@@ -396,8 +396,8 @@ void ZEBinaryBuilder::addProgramSymbols(const IGC::SOpenCLProgramInfo& annotatio
     for (auto sym : symbols.globalStringConst)
         addSymbol(sym, llvm::ELF::STB_GLOBAL, mConstStringSectID);
 
-    // add symbols defined in global section, mGlobalSectID may be unallocated
-    // at this point if symbols are undef
+    // add symbols defined in global section
+    IGC_ASSERT(symbols.global.empty() || mGlobalSectID != -1);
     for (auto sym : symbols.global)
         addSymbol(sym, llvm::ELF::STB_GLOBAL, mGlobalSectID);
 

IGC/BiFModule/Implementation/tileid.cl

@@ -6,7 +6,7 @@ SPDX-License-Identifier: MIT
 
 ============================= end_copyright_notice ===========================*/
 
-extern int *__SubDeviceID;
+__constant int *__SubDeviceID;
 __constant int __MaxHWThreadIDPerSubDevice = 1;
 
 

IGC/Compiler/CISACodeGen/OpenCLKernelCodeGen.cpp

@@ -2208,14 +2208,9 @@ namespace IGC
 
     CVariable* COpenCLKernel::GetGlobalMapping(llvm::Value* c)
     {
-        GlobalVariable* globalVar = cast<GlobalVariable>(c);
-        VISA_Type type = GetType(c->getType());
-
-        if (!globalVar->hasInitializer()) {
-            return GetUndef(type);
-        }
-
         unsigned int val = GetGlobalMappingValue(c);
+
+        VISA_Type type = GetType(c->getType());
         return ImmToVariable(val, type);
     }
 

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

@@ -57,18 +57,6 @@ bool ProgramScopeConstantAnalysis::runOnModule(Module& M)
 
     SmallVector<GlobalVariable*, 32> zeroInitializedGlobals;
 
-    auto getOrAllocateGlobalBuffer = [&]{
-        if (!hasInlineGlobalBuffer)
-        {
-            InlineProgramScopeBuffer ilpsb;
-            ilpsb.alignment = 0;
-            ilpsb.allocSize = 0;
-            m_pModuleMd->inlineGlobalBuffers.push_back(ilpsb);
-            hasInlineGlobalBuffer = true;
-        }
-        return &m_pModuleMd->inlineGlobalBuffers.back().Buffer;
-    };
-
     for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
     {
         GlobalVariable* globalVar = &(*I);
@@ -101,19 +89,25 @@ bool ProgramScopeConstantAnalysis::runOnModule(Module& M)
             continue;
         }
 
-        // Handle external symbols without initializers.
         if (!globalVar->hasInitializer())
         {
-            // Include the variable in 'inlineProgramScopeOffsets'. otherwise
-            // code gen will not emit relocation.
-            inlineProgramScopeOffsets[globalVar] = -1;
+            Value* inst = nullptr;
+            for (auto u : globalVar->users())
+            {
+                if (dyn_cast_or_null<Instruction>(u))
+                {
+                    inst = u;
+                }
+            }
+            std::string ErrorMsg = "Global constant without initializer!";
+            Ctx->EmitError(ErrorMsg.c_str(), inst);
             continue;
         }
 
         // The only way to get a null initializer is via an external variable.
-        // Linking has already occurred; everything should be resolved or
-        // handled before this point.
+        // Linking has already occurred; everything should be resolved.
         Constant* initializer = globalVar->getInitializer();
+        IGC_ASSERT_MESSAGE(initializer, "Constant must be initialized");
         if (!initializer)
         {
             continue;
@@ -133,7 +127,15 @@ bool ProgramScopeConstantAnalysis::runOnModule(Module& M)
         DataVector* inlineProgramScopeBuffer = nullptr;
         if (AS == ADDRESS_SPACE_GLOBAL)
         {
-            inlineProgramScopeBuffer = getOrAllocateGlobalBuffer();
+            if (!hasInlineGlobalBuffer)
+            {
+                InlineProgramScopeBuffer ilpsb;
+                ilpsb.alignment = 0;
+                ilpsb.allocSize = 0;
+                m_pModuleMd->inlineGlobalBuffers.push_back(ilpsb);
+                hasInlineGlobalBuffer = true;
+            }
+            inlineProgramScopeBuffer = &m_pModuleMd->inlineGlobalBuffers.back().Buffer;
         }
         else
         {

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

@@ -134,12 +134,8 @@ bool ProgramScopeConstantResolution::runOnModule(Module& M)
             continue;
         }
 
-        if (!pGlobalVar->hasInitializer())
-        {
-            continue;
-        }
-
         Constant* initializer = pGlobalVar->getInitializer();
+        IGC_ASSERT_MESSAGE(initializer, "Constant must be initialized");
         if (!initializer)
         {
             continue;

IGC/Compiler/Optimizer/OpenCLPasses/UndefinedReferences/UndefinedReferencesPass.cpp

@@ -56,6 +56,8 @@ static bool ExistUndefinedReferencesInModule(Module& module, CodeGenContext *CGC
 {
     bool foundUndef = false;
 
+    std::string msg = "undefined reference to `";
+
     Module::global_iterator GVarIter = module.global_begin();
     for (; GVarIter != module.global_end();)
     {
@@ -64,14 +66,15 @@ static bool ExistUndefinedReferencesInModule(Module& module, CodeGenContext *CGC
         // Increment the iterator before attempting to remove a global variable
         GVarIter++;
 
-        if (pGVar->hasExternalLinkage() || pGVar->hasCommonLinkage())
+        if ((pGVar->hasAtLeastLocalUnnamedAddr() == false) &&
+            (pGVar->hasExternalLinkage() || pGVar->hasCommonLinkage()))
         {
             continue;
         }
 
         if (pGVar->isDeclaration() && pGVar->hasNUsesOrMore(1))
         {
-            ReportUndefinedReference(CGC, pGVar->getName(), pGVar);
+            ReportUndefinedReference(CGC, GVarIter->getName(), pGVar);
             foundUndef = true;
         }