38. A non-transitory, tangible computer readable storage medium, encoded with processor readable instructions to perform a method for processing source code, the method comprising: receiving source code; parsing the source code to obtain a high level intermediate representation of the source code; detecting, in the high level intermediate representation of the source code, high level constructs in the high level intermediate representation of the source code that satisfy constraints for parallel-merging high level constructs; and parallel-merging the high level constructs to generate new high level parallel-merged constructs in a modified high level intermediate representation of the source code that enable runtime operations of the high level constructs to execute in parallel using executable code generated from the modified high level intermediate representation; and executing, if the parallel execution of the runtime operations causes an error, executable code generated from unmodified representations of the high level constructs so the runtime operations of the high level constructs execute sequentially during runtime.
38. A non-transitory, tangible computer readable storage medium, encoded with processor readable instructions to perform a method for processing source code, the method comprising: receiving source code; parsing the source code to obtain a high level intermediate representation of the source code; detecting, in the high level intermediate representation of the source code, high level constructs in the high level intermediate representation of the source code that satisfy constraints for parallel-merging high level constructs; and parallel-merging the high level constructs to generate new high level parallel-merged constructs in a modified high level intermediate representation of the source code that enable runtime operations of the high level constructs to execute in parallel using executable code generated from the modified high level intermediate representation; and executing, if the parallel execution of the runtime operations causes an error, executable code generated from unmodified representations of the high level constructs so the runtime operations of the high level constructs execute sequentially during runtime. 40. The non-transitory, tangible computer readable storage medium of claim 38 , wherein the constraints for parallel-merging high level constructs includes determining that the high level constructs would ordinarily consecutively execute, after being lowered into executable code, as control flow paths that are equivalent in structure and function, and execution traces through the control flow paths in a control flow region of each of the lowered constructs are the same.