[PATCH] Code coverage tool that uses the new coverage mapping format and clang's instrumentation based profiling data

[Justin Bogner]

Alex Lorenz <arphaman at gmail.com> writes:
> The patch provides the initial implementation of the updated code
> coverage tool that uses clang's instrumentation based profiling data
> (the -fprofile-instr-generate option) and the new coverage mapping
> format.
>
> The gcov compatible tool is still there. To invoke the new tool, pass
> the 'show' or 'report' command as the first argument to llvm-cov.
>
> The show command displays the code coverage information for a set of
> source code files of a program. Some of its options follow:
>   -show-expansions - Show macro expansions
>   -show-instantiations - Show template/static functions instantiations
>   -show-regions - Show region markers
>   -show-line-counts - Show execution counts for each line (enabled by default).
>
> The report command displays a couple of code coverage metrics for
> files/functions in a concise table.

I'll review this more thoroughly soon, but I have a couple of high level
comments:

1. It would probably be easier to understand this if it was split into
   two patches: first move the gcov compatible code to its own file and
   update llvm-cov to be a wrapper that always calls into that, and then
   add the new-style support.

2. The semantics for choosing whether to be gcov-compatible are a bit
   confusing. I can see the value of "no recognized command" implying
   compatible behaviour, but going forward we should encourage a saner
   API. Consider:

   - If invoked as gcov (ie, argv[0] is or ends in "gcov"), always be
     gcov compatible.
   - Provide a "gcov" command in addition to "show" and "report", which
     invokes into gcov for the rest of the command line.
   - If no command matches fall back to gcov (perhaps with a warning
     that this usage may be dropped in the future)