frontend/b: fixes for LLVM 4.0 API change

Upstream LLVM added a new parameter to the AllocaInst constructor, which
breaks compilation. Fix it by using the IRBuilder method.
Signed-off-by: Brenden Blanco <bblanco@gmail.com>

src/cc/frontends/b/codegen_llvm.cc

@@ -422,7 +422,8 @@ StatusTuple CodegenLLVM::visit_string_expr_node(StringExprNode *n) {
   if (n->is_lhs()) return mkstatus_(n, "cannot assign to a string");
 
   Value *global = B.CreateGlobalString(n->val_);
-  Value *ptr = new AllocaInst(B.getInt8Ty(), B.getInt64(n->val_.size() + 1), "", resolve_entry_stack());
+  Value *ptr = make_alloca(resolve_entry_stack(), B.getInt8Ty(), "",
+                           B.getInt64(n->val_.size() + 1));
   B.CreateMemCpy(ptr, global, n->val_.size() + 1, 1);
   expr_ = ptr;
 
@@ -813,7 +814,8 @@ StatusTuple CodegenLLVM::visit_table_index_expr_node(TableIndexExprNode *n) {
 
     B.SetInsertPoint(label_then);
     // var Leaf leaf {0}
-    Value *leaf_ptr = B.CreateBitCast(new AllocaInst(leaf_type, "", resolve_entry_stack()), B.getInt8PtrTy());
+    Value *leaf_ptr = B.CreateBitCast(
+        make_alloca(resolve_entry_stack(), leaf_type), B.getInt8PtrTy());
     B.CreateMemSet(leaf_ptr, B.getInt8(0), B.getInt64(n->table_->leaf_id()->bit_width_ >> 3), 1);
     // update(key, leaf)
     B.CreateCall(update_fn, vector<Value *>({pseudo_map_fd, key_ptr, leaf_ptr, B.getInt64(BPF_NOEXIST)}));
@@ -957,7 +959,7 @@ StatusTuple CodegenLLVM::visit_struct_variable_decl_stmt_node(StructVariableDecl
   TRY2(lookup_struct_type(n, &stype, &decl));
 
   Type *ptr_stype = n->is_pointer() ? PointerType::getUnqual(stype) : (PointerType *)stype;
-  AllocaInst *ptr_a = new AllocaInst(ptr_stype, "", resolve_entry_stack());
+  AllocaInst *ptr_a = make_alloca(resolve_entry_stack(), ptr_stype);
   vars_[n] = ptr_a;
 
   if (n->struct_id_->scope_name_ == "proto") {
@@ -1011,7 +1013,8 @@ StatusTuple CodegenLLVM::visit_integer_variable_decl_stmt_node(IntegerVariableDe
     return StatusTuple(0);
 
   // uintX var = init
-  AllocaInst *ptr_a = new AllocaInst(B.getIntNTy(n->bit_width_), n->id_->name_, resolve_entry_stack());
+  AllocaInst *ptr_a = make_alloca(resolve_entry_stack(),
+                                  B.getIntNTy(n->bit_width_), n->id_->name_);
   vars_[n] = ptr_a;
 
   // todo
@@ -1172,9 +1175,9 @@ StatusTuple CodegenLLVM::visit_func_decl_stmt_node(FuncDeclStmtNode *n) {
   string scoped_entry_label = to_string((uintptr_t)fn) + "::entry";
   labels_[scoped_entry_label] = label_entry;
   BasicBlock *label_return = resolve_label("DONE");
-  retval_ = new AllocaInst(fn->getReturnType(), "ret", label_entry);
+  retval_ = make_alloca(label_entry, fn->getReturnType(), "ret");
   B.CreateStore(B.getInt32(0), retval_);
-  errval_ = new AllocaInst(B.getInt64Ty(), "err", label_entry);
+  errval_ = make_alloca(label_entry, B.getInt64Ty(), "err");
   B.CreateStore(B.getInt64(0), errval_);
 
   auto formal = n->formals_.begin();
@@ -1194,7 +1197,7 @@ StatusTuple CodegenLLVM::visit_func_decl_stmt_node(FuncDeclStmtNode *n) {
     // }
 
     // arg->setName((*formal)->id_->name_);
-    // AllocaInst *ptr = new AllocaInst(ptype, nullptr, (*formal)->id_->name_, label_entry);
+    // AllocaInst *ptr = make_alloca(label_entry, ptype, (*formal)->id_->name_);
     // B.CreateStore(arg, ptr);
     // vars_[formal->get()] = ptr;
   }
@@ -1318,5 +1321,23 @@ Instruction * CodegenLLVM::resolve_entry_stack() {
   return &label_entry->back();
 }
 
+AllocaInst *CodegenLLVM::make_alloca(Instruction *Inst, Type *Ty,
+                                     const string &name, Value *ArraySize) {
+  IRBuilderBase::InsertPoint ip = B.saveIP();
+  B.SetInsertPoint(Inst);
+  AllocaInst *a = B.CreateAlloca(Ty, ArraySize, name);
+  B.restoreIP(ip);
+  return a;
+}
+
+AllocaInst *CodegenLLVM::make_alloca(BasicBlock *BB, Type *Ty,
+                                     const string &name, Value *ArraySize) {
+  IRBuilderBase::InsertPoint ip = B.saveIP();
+  B.SetInsertPoint(BB);
+  AllocaInst *a = B.CreateAlloca(Ty, ArraySize, name);
+  B.restoreIP(ip);
+  return a;
+}
+
 }  // namespace cc
 }  // namespace ebpf

src/cc/frontends/b/codegen_llvm.h

@@ -36,6 +36,7 @@ class LLVMContext;
 class Module;
 class StructType;
 class SwitchInst;
+class Type;
 class Value;
 class GlobalVariable;
 }
@@ -91,6 +92,12 @@ class CodegenLLVM : public Visitor {
   llvm::Value * pop_expr();
   llvm::BasicBlock * resolve_label(const string &label);
   llvm::Instruction * resolve_entry_stack();
+  llvm::AllocaInst *make_alloca(llvm::Instruction *Inst, llvm::Type *Ty,
+                                const std::string &name = "",
+                                llvm::Value *ArraySize = nullptr);
+  llvm::AllocaInst *make_alloca(llvm::BasicBlock *BB, llvm::Type *Ty,
+                                const std::string &name = "",
+                                llvm::Value *ArraySize = nullptr);
   StatusTuple lookup_var(Node *n, const std::string &name, Scopes::VarScope *scope,
                          VariableDeclStmtNode **decl, llvm::Value **mem) const;
   StatusTuple lookup_struct_type(StructDeclStmtNode *decl, llvm::StructType **stype) const;