llvm-project/clang/test/Profile
Vedant Kumar dd1ea9de2e Reland: [Coverage] Revise format to reduce binary size
Try again with an up-to-date version of D69471 (99317124 was a stale
revision).

---

Revise the coverage mapping format to reduce binary size by:

1. Naming function records and marking them `linkonce_odr`, and
2. Compressing filenames.

This shrinks the size of llc's coverage segment by 82% (334MB -> 62MB)
and speeds up end-to-end single-threaded report generation by 10%. For
reference the compressed name data in llc is 81MB (__llvm_prf_names).

Rationale for changes to the format:

- With the current format, most coverage function records are discarded.
  E.g., more than 97% of the records in llc are *duplicate* placeholders
  for functions visible-but-not-used in TUs. Placeholders *are* used to
  show under-covered functions, but duplicate placeholders waste space.

- We reached general consensus about giving (1) a try at the 2017 code
  coverage BoF [1]. The thinking was that using `linkonce_odr` to merge
  duplicates is simpler than alternatives like teaching build systems
  about a coverage-aware database/module/etc on the side.

- Revising the format is expensive due to the backwards compatibility
  requirement, so we might as well compress filenames while we're at it.
  This shrinks the encoded filenames in llc by 86% (12MB -> 1.6MB).

See CoverageMappingFormat.rst for the details on what exactly has
changed.

Fixes PR34533 [2], hopefully.

[1] http://lists.llvm.org/pipermail/llvm-dev/2017-October/118428.html
[2] https://bugs.llvm.org/show_bug.cgi?id=34533

Differential Revision: https://reviews.llvm.org/D69471
2020-02-28 18:12:04 -08:00
..
Inputs Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
README
c-avoid-direct-call.c
c-captured.c
c-counter-overflows.c
c-general.c [PGO] Fix buildbot failure in 359215 2019-04-25 21:16:41 +00:00
c-generate.c
c-indirect-call.c
c-linkage-available_externally.c
c-linkage.c
c-outdated-data.c
c-ternary.c
c-unprofiled-blocks.c
c-unprofiled.c
c-unreachable-after-switch.c
cxx-abc-deleting-dtor.cpp [MS] Don't emit coverage for deleting dtors 2019-02-26 20:42:52 +00:00
cxx-class.cpp
cxx-hash-v2.cpp
cxx-implicit.cpp
cxx-indirect-call.cpp
cxx-lambda.cpp
cxx-linkage.cpp
cxx-missing-bodies.cpp
cxx-rangefor.cpp
cxx-stmt-initializers.cpp
cxx-structors.cpp
cxx-templates.cpp [InstrProf] Use separate comdat group for data and counters 2019-02-27 23:38:44 +00:00
cxx-throws.cpp
cxx-virtual-destructor-calls.cpp
def-assignop.cpp Reland: [Coverage] Revise format to reduce binary size 2020-02-28 18:12:04 -08:00
def-ctors.cpp Reland: [Coverage] Revise format to reduce binary size 2020-02-28 18:12:04 -08:00
def-dtors.cpp Reland: [Coverage] Revise format to reduce binary size 2020-02-28 18:12:04 -08:00
func-entry.c
gcc-flag-compatibility.c Update clang tests for new LLVM IR backslash printing in r374415 2019-10-10 18:36:41 +00:00
misexpect-branch-cold.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-branch-nonconst-expected-val.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-branch-unpredictable.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-branch.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-switch-default.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-switch-nonconst.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-switch-only-default-case.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
misexpect-switch.c Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM" 2019-09-11 16:19:50 +00:00
objc-general.m
profile-does-not-exist.c
profile-summary.c

README

These are tests for instrumentation based profiling.  This specifically means
the -fprofile-instr-generate and -fprofile-instr-use driver flags.

Tests in this directory should usually test both:

  - the generation of instrumentation (-fprofile-instr-generate), and
  - the use of profile data from instrumented runs (-fprofile-instr-use).

In order to test -fprofile-instr-use without actually running an instrumented
program, .profdata files are checked into Inputs/.

The input source files must include a main function such that building with
-fprofile-instr-generate and running the resulting program generates the same
.profdata file that is consumed by the tests for -fprofile-instr-use.  Even
tests that only check -fprofile-instr-use should include such a main function,
so that profile data can be regenerated as the .profdata file format evolves.