Use slot_getattr wrapper function for regular version.(#1194)

Slot_getattr in header file cause to have different pointer.
This cause issue when we register as external function. LLVM
expect the name of the external function to be unique for
each pointer. In order to fix it, we introduced wrapper function
in codegen_wrapper.cc and use that instead of slot_getattr.

src/backend/codegen/codegen_wrapper.cc

@@ -102,6 +102,11 @@ void SetActiveCodeGeneratorManager(void* manager) {
   ActiveCodeGeneratorManager = manager;
 }
 
+Datum
+slot_getattr_regular(TupleTableSlot *slot, int attnum, bool *isnull) {
+  return slot_getattr(slot, attnum, isnull);
+}
+
 void* ExecVariableListCodegenEnroll(
     ExecVariableListFn regular_func_ptr,
     ExecVariableListFn* ptr_to_chosen_func_ptr,

src/backend/codegen/exec_eval_expr_codegen.cc

@@ -123,8 +123,8 @@ bool ExecEvalExprCodegen::GenerateExecEvalExpr(
   if (nullptr == slot_getattr_codegen_ ||
       false == slot_getattr_codegen_->GenerateCode(codegen_utils)) {
     gen_info_.llvm_slot_getattr_func =
-        codegen_utils->GetOrRegisterExternalFunction(slot_getattr,
-                                                     "slot_getattr");
+        codegen_utils->GetOrRegisterExternalFunction(slot_getattr_regular,
+                                                     "slot_getattr_regular");
   } else {
     gen_info_.llvm_slot_getattr_func =
         slot_getattr_codegen_->GetGeneratedFunction();

src/backend/codegen/include/codegen/codegen_manager.h

@@ -81,13 +81,12 @@ class CodegenManager {
       FuncType regular_func_ptr,
       FuncType* ptr_to_chosen_func_ptr,
       Args&&... args) {  // NOLINT(build/c++11)
-
-	assert(nullptr != regular_func_ptr);
-	assert(nullptr != ptr_to_chosen_func_ptr);
+    assert(nullptr != regular_func_ptr);
+    assert(nullptr != ptr_to_chosen_func_ptr);
 
     bool can_enroll =
         // manager may be NULL if ExecInitNode/ExecProcNode weren't previously
-    	// called. This happens e.g during gpinitsystem.
+        // called. This happens e.g during gpinitsystem.
         (nullptr != manager) &&
         codegen &&  // if codegen guc is false
         // if generator is disabled

src/backend/codegen/include/codegen/slot_getattr_codegen.h

@@ -104,7 +104,8 @@ class SlotGetAttrCodegen : public BaseCodegen<SlotGetAttrFn> {
   SlotGetAttrCodegen(gpcodegen::CodegenManager* manager,
                      TupleTableSlot* slot,
                      int max_attr)
-  : BaseCodegen(manager, kSlotGetAttrPrefix, slot_getattr, &dummy_func_),
+  : BaseCodegen(
+      manager, kSlotGetAttrPrefix, slot_getattr_regular, &dummy_func_),
     slot_(slot),
     max_attr_(max_attr),
     llvm_function_(nullptr) {

src/backend/codegen/slot_getattr_codegen.cc

@@ -685,8 +685,8 @@ bool SlotGetAttrCodegen::GenerateSlotGetAttr(
       llvm_error);
 
   codegen_utils->CreateFallback<SlotGetAttrFn>(
-      codegen_utils->GetOrRegisterExternalFunction(slot_getattr,
-                                                   "slot_getattr"),
+      codegen_utils->GetOrRegisterExternalFunction(slot_getattr_regular,
+                                                   "slot_getattr_regular"),
       slot_getattr_func);
   return true;
 }

src/include/codegen/codegen_wrapper.h

@@ -161,6 +161,12 @@ GetActiveCodeGeneratorManager();
 void
 SetActiveCodeGeneratorManager(void* manager);
 
+/*
+ * Wrapper function for slot_getattr.
+ */
+Datum
+slot_getattr_regular(struct TupleTableSlot *slot, int attnum, bool *isnull);
+
 /*
  * returns the pointer to the ExecVariableList
  */