Vedant Kumar 1ce7fd2110 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
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Inputs	Reland: [Coverage] Revise format to reduce binary size	2020-02-28 18:12:04 -08:00
binary-formats.c	Reland: [Coverage] Revise format to reduce binary size	2020-02-28 18:12:04 -08:00
combine_expansions.cpp
copy_block_helper.m
cov-comdat.test
deferred-region.cpp
demangle.test
dir-with-filtering.test
double_dots.c
export_functions-lcov.test
export_functions.test
gcov47_compatibility.cpp
hideUnexecutedSubviews.test
ifdef.c
ignore-filename-regex.test
lit.local.cfg
llvm-cov.test
load-multiple-objects.test
multiple-files.test
multiple-objects-not-all-instrumented.test
multiple-objects.test
multithreaded-report.test
name_whitelist.test
native_separators.c
path_equivalence.c
prefer_used_to_unused.h
prevent_false_instantiations.h
range_based_for.cpp
report.cpp
scan-directory.test
showExpansions.cpp
showHighlightedRanges.cpp
showLineExecutionCounts-lcov.test
showLineExecutionCounts.cpp
showProjectSummary.cpp
showRegionMarkers.cpp
showTabsHTML.cpp
showTemplateInstantiations.cpp
sources-specified.test
style.test
threads.c
universal_bin_wrapping_archives.test
universal-binary.c
warnings.h
zeroFunctionFile.c