1. A method for helping to localize an error observed by running a first testcase made up of instructions that write to a set of data storage locations, the method comprising: performing a first run of the first testcase on a hardware version of a processor along a first execution path to yield first testcase-run results in the form of a first set of values respectively stored in the set of data storage locations; performing a second run of the first testcase on a software model version of the processor along a second execution path to yield second testcase-run results in the form of a second set of values respectively stored in the set of data storage locations; recording control flow information during the second run of the first testcase; determining a set of miscompare data storage location(s), including at least a first miscompare data storage location, by comparing the first set of values and the second set of values; generating a first modified version of the first testcase that, when executed on the software model version of the processor, will produce a third execution path different from the second execution path, the modified version of the first testcase based on: (i) the set of miscompare data storage location(s), and/or (ii) the control flow information; performing a first run of the first modified version of the first testcase on the software model version of the processor along the third execution path to yield third testcase-run results in the form of a third set of values respectively stored in the set of data storage locations; and comparing the first set of values and the third set of values to provide an indication of similarity between the first execution path and the third execution path.