When I used to do firmware, we used to see tons of bugs in the commercial compilers. We try out a new version and one bug was fixed and a new one inevitably pop

When I used to do firmware, we used to see tons of bugs in the commercial compilers. We try out a new version and one bug was fixed and a new one inevitably pops up. My first boss used to do a diff between the assembly output of both versions for the same source code to identify the differences and determine if any new bugs were added.