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authorGreg Hackmann <ghackmann@android.com>2019-05-15 00:45:31 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-15 04:52:51 +0200
commite178a5beb36960902379040ee0b667fb0a8eee93 (patch)
tree03b2302179b767410a313fdf9003e9e5dce702e8 /kernel/printk
parentgcov: docs: add a note on GCC vs Clang differences (diff)
downloadlinux-e178a5beb36960902379040ee0b667fb0a8eee93.tar.xz
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gcov: clang support
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(). [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20190417225328.208129-1-trong@android.com Signed-off-by: Greg Hackmann <ghackmann@android.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Tri Vo <trong@android.com> Co-developed-by: Nick Desaulniers <ndesaulniers@google.com> Co-developed-by: Tri Vo <trong@android.com> Tested-by: Trilok Soni <tsoni@quicinc.com> Tested-by: Prasad Sodagudi <psodagud@quicinc.com> Tested-by: Tri Vo <trong@android.com> Tested-by: Daniel Mentz <danielmentz@google.com> Tested-by: Petri Gynther <pgynther@google.com> Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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