Fix null dereferences

Refactor potential null dereferences or assert that values
aren't null in suspicious places.

Author: fda0

IGC/VectorCompiler/lib/GenXCodeGen/GenXLowering.cpp

@@ -4486,6 +4486,7 @@ bool GenXLowering::lowerLogicalThreadID(CallInst *CI) {
 
   if (!isPowerOf2_32(NumThreads)) {
     IGC_ASSERT_EXIT(Res);
+    IGC_ASSERT_EXIT(TID);
     auto *Mul = IRB.CreateMul(Res, ConstantInt::get(Ty, NumThreads));
     Res = IRB.CreateAdd(Mul, TID);
   }

IGC/VectorCompiler/lib/InternalIntrinsics/InternalIntrinsics.cpp

@@ -443,6 +443,9 @@ getIntrinsicInfoTableEntries(InternalIntrinsic::ID id,
 /// parse ffXX as f(fXX) or f(fX)X.  (X is a placeholder for any other type.)
 static std::string getMangledTypeStr(Type *Ty) {
   std::string Result;
+  if (!Ty)
+    return Result;
+
   if (PointerType *PTyp = dyn_cast<PointerType>(Ty)) {
     Result += "p" + utostr(PTyp->getAddressSpace()) +
               getMangledTypeStr(IGCLLVM::getNonOpaquePtrEltTy(PTyp));
@@ -469,7 +472,7 @@ static std::string getMangledTypeStr(Type *Ty) {
     Result += "v" +
               utostr(cast<IGCLLVM::FixedVectorType>(Ty)->getNumElements()) +
               getMangledTypeStr(cast<VectorType>(Ty)->getElementType());
-  else if (Ty)
+  else
     Result += EVT::getEVT(Ty).getEVTString();
   return Result;
 }

visa/GraphColor.cpp

@@ -3659,10 +3659,12 @@ void Augmentation::buildLiveIntervals() {
         G4_Declare *defdcl = GetTopDclFromRegRegion(dst);
 
         if (dst->getBase()->isRegAllocPartaker()) {
-          if (defdcl && gra.getLocalLR(defdcl)) {
-            updateStartIntervalForLocal(defdcl, inst, dst);
-          } else {
-            updateStartInterval(defdcl, inst);
+          if (defdcl) {
+            if (gra.getLocalLR(defdcl)) {
+              updateStartIntervalForLocal(defdcl, inst, dst);
+            } else {
+              updateStartInterval(defdcl, inst);
+            }
           }
         } else if (liveAnalysis.livenessClass(G4_GRF)) {
           LocalLiveRange *defdclLR;