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SubjectRe: [PATCH v5] gcov: Clang support
On Wed, Apr 17, 2019 at 4:21 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 17 Apr 2019 15:53:28 -0700 Tri Vo <trong@android.com> wrote:
>
> > LLVM uses profiling data that's deliberately similar to GCC, but has a very
> > different way of exporting that data. LLVM calls llvm_gcov_init() once per
> > module, and provides a couple of callbacks that we can use to ask for more
> > data.
> >
> > We care about the "writeout" callback, which in turn calls back into
> > compiler-rt/this module to dump all the gathered coverage data to disk:
> >
> > llvm_gcda_start_file()
> > llvm_gcda_emit_function()
> > llvm_gcda_emit_arcs()
> > llvm_gcda_emit_function()
> > llvm_gcda_emit_arcs()
> > [... repeats for each function ...]
> > llvm_gcda_summary_info()
> > llvm_gcda_end_file()
> >
> > This design is much more stateless and unstructured than gcc's, and is
> > intended to run at process exit. This forces us to keep some local state
> > about which module we're dealing with at the moment. On the other hand, it
> > also means we don't depend as much on how LLVM represents profiling data
> > internally.
> >
> > See LLVM's lib/Transforms/Instrumentation/GCOVProfiling.cpp for more
> > details on how this works, particularly GCOVProfiler::emitProfileArcs(),
> > GCOVProfiler::insertCounterWriteout(), and GCOVProfiler::insertFlush().
>
> checkpatch speaketh truth.
>
> Also, I'll change those Co-authored-by's to the documented Co-developed-by.
>
>
> From: Andrew Morton <akpm@linux-foundation.org>
> Subject: gcov-clang-support-checkpatch-fixes
>
> WARNING: Non-standard signature: Co-authored-by:
> #31:
> Co-authored-by: Nick Desaulniers <ndesaulniers@google.com>
>
> WARNING: Non-standard signature: Co-authored-by:
> #32:
> Co-authored-by: Tri Vo <trong@android.com>
>
> WARNING: Possible unnecessary 'out of memory' message
> #158: FILE: kernel/gcov/clang.c:90:
> + if (!info) {
> + pr_warn_ratelimited("failed to allocate gcov info\n");
>
> WARNING: Possible unnecessary 'out of memory' message
> #193: FILE: kernel/gcov/clang.c:125:
> + if (!info) {
> + pr_warn_ratelimited("failed to allocate gcov function info for %s\n",
>
> WARNING: line over 80 characters
> #546: FILE: kernel/gcov/clang.c:478:
> + pos += store_gcov_u32(buffer, pos, fi_ptr->cfg_checksum);
>
> total: 0 errors, 5 warnings, 663 lines checked
>
> NOTE: For some of the reported defects, checkpatch may be able to
> mechanically convert to the typical style using --fix or --fix-inplace.
>
> ./patches/gcov-clang-support.patch has style problems, please review.
>
> NOTE: If any of the errors are false positives, please report
> them to the maintainer, see CHECKPATCH in MAINTAINERS.
>
> Please run checkpatch prior to sending patches

Thanks! I'll keep that in mind.

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