Constant fold with 0 for OOB access to immediate constant buffer

Change-Id: I5ff335d0b540ec0cb19dbb61f83cd5ea64c5aace

Author: srividyakarumuri

IGC/Compiler/CISACodeGen/helper.cpp

@@ -599,7 +599,7 @@ namespace IGC
         return false;
     }
 
-    bool EvalConstantAddress(Value* address, unsigned int& offset, const llvm::DataLayout* pDL, Value* ptrSrc)
+    bool EvalConstantAddress(Value* address, int& offset, const llvm::DataLayout* pDL, Value* ptrSrc)
     {
 
         if ((ptrSrc == nullptr && isa<ConstantPointerNull>(address)) ||
@@ -616,7 +616,7 @@ namespace IGC
                 ConstantInt* eltIdx = dyn_cast<ConstantInt>(eltIdxVal);
                 if (!eltIdx)
                     return false;
-                offset = int_cast<unsigned>(eltIdx->getZExtValue());
+                offset = int_cast<int>(eltIdx->getZExtValue());
                 return true;
             }
         }
@@ -633,7 +633,7 @@ namespace IGC
                 ConstantInt * eltIdx = dyn_cast<ConstantInt>(eltIdxVal);
                 if (!eltIdx)
                     return false;
-                offset = int_cast<unsigned>(eltIdx->getZExtValue());
+                offset = int_cast<int>(eltIdx->getZExtValue());
                 return true;
             }
             else if (ptrExpr->getOpcode() == Instruction::GetElementPtr)
@@ -650,14 +650,14 @@ namespace IGC
                     if (StructType * StTy = GTI.getStructTypeOrNull()) {
                         unsigned Field = int_cast<unsigned>(cast<ConstantInt>(Idx)->getZExtValue());
                         if (Field) {
-                            offset += int_cast<unsigned int>(pDL->getStructLayout(StTy)->getElementOffset(Field));
+                            offset += int_cast<int>(pDL->getStructLayout(StTy)->getElementOffset(Field));
                         }
                         Ty = StTy->getElementType(Field);
                     }
                     else {
                         Ty = GTI.getIndexedType();
                         if (const ConstantInt * CI = dyn_cast<ConstantInt>(Idx)) {
-                            offset += int_cast<unsigned int>(
+                            offset += int_cast<int>(
                             pDL->getTypeAllocSize(Ty) * CI->getSExtValue());
 
                         }

IGC/Compiler/CISACodeGen/helper.h

@@ -158,7 +158,7 @@ namespace IGC
     bool GetGRFOffsetFromRTV(llvm::Value* pointerSrc, unsigned& GRFOffset);
     bool GetStatelessBufferInfo(llvm::Value* pointer, unsigned& bufIdOrGRFOffset, IGC::BufferType& bufferTy, llvm::Value*& bufferSrcPtr, bool& isDirectBuf);
     // try to evaluate the address if it is constant.
-    bool EvalConstantAddress(llvm::Value* address, unsigned int& offset, const llvm::DataLayout* pDL, llvm::Value* ptrSrc = nullptr);
+    bool EvalConstantAddress(llvm::Value* address, int& offset, const llvm::DataLayout* pDL, llvm::Value* ptrSrc = nullptr);
 
 
     bool isSampleLoadGather4InfoInstruction(llvm::Instruction* inst);

IGC/Compiler/CustomSafeOptPass.cpp

@@ -2565,7 +2565,7 @@ Constant* IGCConstProp::replaceShaderConstant(LoadInst* inst)
     if (modMD && ((directBuf && (bufType == CONSTANT_BUFFER)) || statelessBuf))
     {
         Value* ptrVal = inst->getPointerOperand();
-        unsigned eltId = 0;
+        int eltId = 0;
         size_in_bytes = (unsigned int)inst->getType()->getPrimitiveSizeInBits() / 8;
         if (!EvalConstantAddress(ptrVal, eltId, m_TD, pointerSrc))
         {
@@ -2586,18 +2586,36 @@ Constant* IGCConstProp::replaceShaderConstant(LoadInst* inst)
                     uint32_t eltSize_in_bytes = (unsigned int)srcEltTy->getPrimitiveSizeInBits() / 8;
                     IRBuilder<> builder(inst);
                     Value* vectorValue = UndefValue::get(inst->getType());
+                    char* pEltValue;        // Pointer to element value
                     for (uint i = 0; i < srcNElts; i++)
                     {
+                        if (eltId < 0 || eltId >= (int)modMD->immConstant.data.size())
+                        {
+                            int OOBvalue = 0;       // OOB access to immediate constant buffer should return 0
+                            char* pOOBvalue = (char*)& OOBvalue;    // Pointer to value 0 which is a OOB access value
+                            pEltValue = pOOBvalue;
+                        }
+                        else
+                            pEltValue = offset + eltId + (i * eltSize_in_bytes);
                         vectorValue = builder.CreateInsertElement(
                             vectorValue,
-                            GetConstantValue(srcEltTy, offset + eltId + (i * eltSize_in_bytes)),
+                            GetConstantValue(srcEltTy, pEltValue),
                             builder.getInt32(i));
                     }
                     return dyn_cast<Constant>(vectorValue);
                 }
                 else
                 {
-                    return GetConstantValue(inst->getType(), offset + eltId);
+                    char* pEltValue;        // Pointer to element value
+                    if (eltId < 0 || eltId >= (int)modMD->immConstant.data.size())
+                    {
+                        int OOBvalue = 0;       // OOB access to immediate constant buffer should return 0
+                        char* pOOBvalue = (char*)& OOBvalue;    // Pointer to value 0 which is a OOB access value
+                        pEltValue = pOOBvalue;
+                    }
+                    else
+                        pEltValue = offset + eltId;
+                    return GetConstantValue(inst->getType(), pEltValue);
                 }
             }
             else if ((!IGC_IS_FLAG_ENABLED(DisableDynamicConstantFolding)) && (modMD->inlineDynConstants.size() > 0))

IGC/Compiler/FindInterestingConstants.cpp

@@ -192,7 +192,7 @@ void FindInterestingConstants::FoldsToSourcePropagate(llvm::Instruction* I)
 }
 
 // Get constant address from load instruction
-bool FindInterestingConstants::getConstantAddress(llvm::LoadInst& I, unsigned& bufIdOrGRFOffset, unsigned& eltId, int& size_in_bytes)
+bool FindInterestingConstants::getConstantAddress(llvm::LoadInst& I, unsigned& bufIdOrGRFOffset, int& eltId, int& size_in_bytes)
 {
     // Check if the load instruction is with constant buffer address
     unsigned as = I.getPointerAddressSpace();
@@ -306,7 +306,7 @@ void FindInterestingConstants::visitLoadInst(llvm::LoadInst& I)
     }
 
     unsigned bufIdOrGRFOffset;
-    unsigned eltId;
+    int eltId;
     int size_in_bytes;
 
     m_foldsToZero = 0;

IGC/Compiler/FindInterestingConstants.h

@@ -70,7 +70,7 @@ namespace IGC
         const llvm::DataLayout* m_DL;
 
         // Helper functions
-        bool getConstantAddress(llvm::LoadInst& I, unsigned& bufIdOrGRFOffset, unsigned& eltId, int& size_in_bytes);
+        bool getConstantAddress(llvm::LoadInst& I, unsigned& bufIdOrGRFOffset, int& eltId, int& size_in_bytes);
         bool FoldsToConst(llvm::Instruction* inst, llvm::Instruction* use, bool& propagate);
         bool FoldsToZero(llvm::Instruction* inst, llvm::Instruction* use);
         bool FoldsToSource(llvm::Instruction* inst, llvm::Instruction* use);