Embodiments are directed to tracking variable location information in optimized code and efficiently collecting and storing reaching definition information. A computer system receives a portion of source code at a compiler, where the compiler is configured to compile and optimize the source code for execution. The computer system tags selected variables in the source code with a tag, where the tag is configured to provide location information for the variable. The computer system optimizes the received portion of source code including changing at least one of the tagged variables. The computer system also tracks the tagged variables as the variables are changed by the compiler during code optimization and persists the variable location information, so that the persisted variable location information is available to other compiler components.