LLVM 5.0 and 6.0 compatibility (cmu-db#1389)

* Preliminary pass at LLVM 6 API changes. References:

http://lists.llvm.org/pipermail/llvm-dev/2015-August/089706.html
https://reviews.llvm.org/rL298010
https://stackoverflow.com/questions/46367910/llvm-5-0-linking-error-with-llvmmoduledump

* Preliminary pass at packages.sh changes for Ubuntu 18.04 LTS. Fixed include issue in udf_parser under Ubuntu 18.04.

* Revert "Preliminary pass at packages.sh changes for Ubuntu 18.04 LTS."

This reverts commit a40ca21

We want to do packages.sh changes separately.

* Add LLVM version check around AllocaInst().

Author: mbutrovich

src/codegen/codegen.cpp

@@ -91,11 +91,19 @@ llvm::Value *CodeGen::AllocateVariable(llvm::Type *type,
   // matter where we insert it.
 
   auto *entry_block = code_context_.GetCurrentFunction()->GetEntryBlock();
+#if LLVM_VERSION_GE(5, 0)
+  if (entry_block->empty()) {
+    return new llvm::AllocaInst(type, 0, name, entry_block);
+  } else {
+    return new llvm::AllocaInst(type, 0, name, &entry_block->front());
+  }
+#else
   if (entry_block->empty()) {
     return new llvm::AllocaInst(type, name, entry_block);
   } else {
     return new llvm::AllocaInst(type, name, &entry_block->front());
   }
+#endif
 }
 
 llvm::Value *CodeGen::AllocateBuffer(llvm::Type *element_type,

src/codegen/function_builder.cpp

@@ -143,7 +143,7 @@ FunctionBuilder::~FunctionBuilder() {
 // Here, we just need to iterate over the arguments in the function to find a
 // match. The names of the arguments were provided and set at construction time.
 llvm::Value *FunctionBuilder::GetArgumentByName(std::string name) {
-  for (auto &arg : func_->getArgumentList()) {
+  for (auto &arg : func_->args()) {
     if (arg.getName().equals(name)) {
       return &arg;
     }

src/udf/udf_parser.cpp

@@ -13,6 +13,7 @@
 #include "udf/udf_parser.h"
 
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/raw_ostream.h"
 
 #include "codegen/codegen.h"
 
@@ -45,7 +46,7 @@ void UDFParser::ParseUDF(codegen::CodeGen &cg, codegen::FunctionBuilder &fb,
       code_context.SetUDF(func_ptr);
 
       // To check correctness of the codegened UDF
-      func_ptr->dump();
+      func_ptr->print(llvm::errs(), nullptr);
     }
   }
 }