Method GetCodegendComputeFnImpl

be/src/exprs/conditional-functions.cc:51–101

Sample IR output: define i16 @IfExpr(%"class.impala::ScalarExprEvaluator"* %eval, %"class.impala::TupleRow"* %row) #47 { is_condition_null: %condition = call i16 @"impala::Operators::Gt_BigIntVal_BigIntValWrapper"( %"class.impala::ScalarExprEvaluator"* %eval, %"class.impala::TupleRow"* %row) %is_null = trunc i16 %condition to i1 br i1 %is_null, label %return_else, label %eval_condition eval_condi

///   ret i16 %else_val
/// }
Status IfExpr::GetCodegendComputeFnImpl(LlvmCodeGen* codegen, llvm::Function** fn) {
  constexpr int IF_NUM_CHILDREN = 3;
  DCHECK_EQ(IF_NUM_CHILDREN, GetNumChildren());

  llvm::Function* child_fns[IF_NUM_CHILDREN];
  for (int i = 0; i < IF_NUM_CHILDREN; ++i) {
    RETURN_IF_ERROR(GetChild(i)->GetCodegendComputeFn(codegen, false, &child_fns[i]));
  }

  llvm::LLVMContext& context = codegen->context();
  LlvmBuilder builder(context);

  llvm::Value* args[2];
  llvm::Function* function = CreateIrFunctionPrototype("IfExpr", codegen, &args);

  llvm::BasicBlock* is_condition_null_block = llvm::BasicBlock::Create(
      context, "is_condition_null", function);
  llvm::BasicBlock* eval_condition_block = llvm::BasicBlock::Create(
      context, "eval_condition", function);
  llvm::BasicBlock* return_then_block = llvm::BasicBlock::Create(
      context, "return_then", function);
  llvm::BasicBlock* return_else_block = llvm::BasicBlock::Create(
      context, "return_else", function);

  // Check if the condition is a null value.
  builder.SetInsertPoint(is_condition_null_block);
  CodegenAnyVal condition = CodegenAnyVal::CreateCallWrapped(
      codegen, &builder, children()[0]->type(), child_fns[0], args, "condition");
  builder.CreateCondBr(
      condition.GetIsNull(), return_else_block, eval_condition_block);

  // Condition is non-null, branch according to its value.
  builder.SetInsertPoint(eval_condition_block);
  builder.CreateCondBr(condition.GetVal(), return_then_block, return_else_block);

  // Eval and return then value.
  builder.SetInsertPoint(return_then_block);
  llvm::Value* then_val =
      CodegenAnyVal::CreateCall(codegen, &builder, child_fns[1], args, "then_val");
  builder.CreateRet(then_val);

  // Eval and return else value.
  builder.SetInsertPoint(return_else_block);
  llvm::Value* else_val =
      CodegenAnyVal::CreateCall(codegen, &builder, child_fns[2], args, "else_val");
  builder.CreateRet(else_val);

  *fn = codegen->FinalizeFunction(function);
  if (UNLIKELY(*fn == nullptr)) return Status(TErrorCode::IR_VERIFY_FAILED, "IfExpr");
  return Status::OK();
}

/// Sample IR output for three columns:
/// define i64 @CoalesceExpr(%"class.impala::ScalarExprEvaluator"* %eval,