Address some static analyzer concerns

The assertions are actually not required here, since all these
functions are being called from visitCallInst, which has the
appropriate check. But for the code consistency lets do not
trust functions' inputs.

Signed-off-by: Dmitry Sidorov <dmitry.sidorov@intel.com>

Author: MrSidims

lib/SPIRV/SPIRVToOCL.cpp

@@ -596,6 +596,7 @@ void SPIRVToOCLBase::visitCallSPIRVImageMediaBlockBuiltin(CallInst *CI, Op OC) {
 }
 void SPIRVToOCLBase::visitCallBuildNDRangeBuiltIn(CallInst *CI, Op OC,
                                                   StringRef DemangledName) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -625,6 +626,7 @@ void SPIRVToOCLBase::visitCallBuildNDRangeBuiltIn(CallInst *CI, Op OC,
 
 void SPIRVToOCLBase::visitCallGenericCastToPtrExplicitBuiltIn(CallInst *CI,
                                                               Op OC) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -651,6 +653,7 @@ void SPIRVToOCLBase::visitCallGenericCastToPtrExplicitBuiltIn(CallInst *CI,
 
 void SPIRVToOCLBase::visitCallSPIRVCvtBuiltin(CallInst *CI, Op OC,
                                               StringRef DemangledName) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -677,6 +680,7 @@ void SPIRVToOCLBase::visitCallSPIRVCvtBuiltin(CallInst *CI, Op OC,
 }
 
 void SPIRVToOCLBase::visitCallAsyncWorkGroupCopy(CallInst *CI, Op OC) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -690,6 +694,7 @@ void SPIRVToOCLBase::visitCallAsyncWorkGroupCopy(CallInst *CI, Op OC) {
 }
 
 void SPIRVToOCLBase::visitCallGroupWaitEvents(CallInst *CI, Op OC) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -962,6 +967,7 @@ void SPIRVToOCLBase::visitCallSPIRVGenericPtrMemSemantics(CallInst *CI) {
 }
 
 void SPIRVToOCLBase::visitCallSPIRVBuiltin(CallInst *CI, Op OC) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -973,6 +979,7 @@ void SPIRVToOCLBase::visitCallSPIRVBuiltin(CallInst *CI, Op OC) {
 
 void SPIRVToOCLBase::visitCallSPIRVBuiltin(CallInst *CI,
                                            SPIRVBuiltinVariableKind Kind) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -984,6 +991,7 @@ void SPIRVToOCLBase::visitCallSPIRVBuiltin(CallInst *CI,
 
 void SPIRVToOCLBase::visitCallSPIRVAvcINTELInstructionBuiltin(CallInst *CI,
                                                               Op OC) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -994,6 +1002,7 @@ void SPIRVToOCLBase::visitCallSPIRVAvcINTELInstructionBuiltin(CallInst *CI,
 }
 
 void SPIRVToOCLBase::visitCallSPIRVOCLExt(CallInst *CI, OCLExtOpKind Kind) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -1004,6 +1013,7 @@ void SPIRVToOCLBase::visitCallSPIRVOCLExt(CallInst *CI, OCLExtOpKind Kind) {
 }
 
 void SPIRVToOCLBase::visitCallSPIRVVLoadn(CallInst *CI, OCLExtOpKind Kind) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -1022,6 +1032,7 @@ void SPIRVToOCLBase::visitCallSPIRVVLoadn(CallInst *CI, OCLExtOpKind Kind) {
 }
 
 void SPIRVToOCLBase::visitCallSPIRVVStore(CallInst *CI, OCLExtOpKind Kind) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   mutateCallInstOCL(
       M, CI,
@@ -1060,6 +1071,7 @@ void SPIRVToOCLBase::visitCallSPIRVVStore(CallInst *CI, OCLExtOpKind Kind) {
 }
 
 void SPIRVToOCLBase::visitCallSPIRVPrintf(CallInst *CI, OCLExtOpKind Kind) {
+  assert(CI->getCalledFunction() && "Unexpected indirect call");
   AttributeList Attrs = CI->getCalledFunction()->getAttributes();
   CallInst *NewCI = mutateCallInstOCL(
       M, CI,