Commit Graph

181 Commits

Author SHA1 Message Date
Aaron Ballman 0dd49a5628 Use functions with prototypes when appropriate; NFC
A significant number of our tests in C accidentally use functions
without prototypes. This patch converts the function signatures to have
a prototype for the situations where the test is not specific to K&R C
declarations. e.g.,

  void func();

becomes

  void func(void);

This is the eighth batch of tests being updated (there are a
significant number of other tests left to be updated).
2022-02-12 07:25:06 -05:00
David Tenty 9939bb6682 [NFC][AIX][clang] un-XFAIL gcc profile flag compat test
We can pass this test now thanks to recent changes that allow us to use PGO without LTO, so un-XFAIL the test and update the comments.

Differential Revision: https://reviews.llvm.org/D118474
2022-01-28 11:18:55 -05:00
hyeongyu kim 4608b1d726 Resolve lit failures in clang-aarch64* 2022-01-16 23:06:05 +09:00
hyeongyu kim 1b1c8d83d3 [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169
2022-01-16 18:54:17 +09:00
Ellis Hoag de11de308b [InstrProf] Use i32 for GEP index from lowering llvm.instrprof.increment
The `llvm.instrprof.increment` intrinsic uses `i32` for the index. We should use this same type for the index into the GEP instructions.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D114268
2021-11-19 15:45:14 -08:00
hyeongyu kim fd9b099906 Revert "[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default"
This reverts commit aacfbb953e.

Revert "Fix lit test failures in CodeGenCoroutines"

This reverts commit 63fff0f5bf.
2021-11-09 02:15:55 +09:00
hyeongyukim aacfbb953e [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169

[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2)

This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:

(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.

(2) The remaining tests are updated manually.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D108453

Resolve lit failures in clang after 8ca4b3e's land

Fix lit test failures in clang-ppc* and clang-x64-windows-msvc

Fix missing failures in clang-ppc64be* and retry fixing clang-x64-windows-msvc

Fix internal_clone(aarch64) inline assembly
2021-11-06 19:19:22 +09:00
Juneyoung Lee 89ad2822af Revert "[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default"
This reverts commit 7584ef766a.
2021-11-06 15:39:19 +09:00
Juneyoung Lee 7584ef766a [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default
Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions.
I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default.

Test updates are made as a separate patch: D108453

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D105169
2021-11-06 15:36:42 +09:00
Arthur Eubanks cb5a10199b [test] Remove tests pinned to the legacy PM
Now that the legacy PM is deprecated for the optimization pipeline, we
can start deleting legacy PM tests.

For tests that test both PMs, merge the RUN lines.
Delete tests specific to the legacy PM.
2021-10-18 16:40:46 -07:00
Juneyoung Lee f193bcc701 Revert D105169 due to the two-stage failure in ASAN
This reverts the following commits:
37ca7a795b
9aa6c72b92
705387c507
8ca4b3ef19
80dba72a66
2021-10-18 23:52:46 +09:00
Juneyoung Lee 705387c507 Resolve lit failures in clang after 8ca4b3e's land 2021-10-16 13:51:50 +09:00
Juneyoung Lee 8ca4b3ef19 [Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default (2)
This patch updates test files after D105169.
Autogenerated test codes are changed by `utils/update_cc_test_checks.py,` and non-autogenerated test codes are changed as follows:

(1) I wrote a python script that (partially) updates the tests using regex: {F18594904} The script is not perfect, but I believe it gives hints about which patterns are updated to have `noundef` attached.

(2) The remaining tests are updated manually.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D108453
2021-10-16 12:01:41 +09:00
Jinsong Ji 25c30324e9 [AIX] Change the linkage of profiling counter/data to be private
We generate symbols like `profc`/`profd` for each function, and put them into csects.
When there are weak functions,  we generate weak symbols for the functions as well,
with ELF (and some others),  linker (binder) will discard and only keep one copy of the weak symbols.

However, on AIX, the current binder can NOT discard the weak symbols if we put all of them into the same csect,
as binder can NOT discard a subset of a csect.

This creates a unique challenge for using those symbols to calculate some relative offsets.

This patch changed the linkage of `profc`/`profd` symbols to be private, so that all the profc/profd for each weak symbol will be *local* to objects, and all kept in the csect, so we won't have problem. Although only one of the counters will be used, all the pointer in the profd is correct.

The downside is that we won't be able to discard the duplicated counters and profile data,
but those can not be discarded even if we keep the weak linkage,
due to the binder limitation of not discarding a subsect of the csect either .

Reviewed By: Whitney, MaskRay

Differential Revision: https://reviews.llvm.org/D110422
2021-09-29 00:47:25 +00:00
Mark Danial 39ca3e5541 Update: clang/test/Profile/gcc-flag-compatibility.c to have -flto on AIX
Reviewed By: Whitney

Differential Revision: https://reviews.llvm.org/D106815
2021-08-09 14:57:38 +00:00
Fangrui Song a1532ed275 [InstrProfiling] Make CountersPtr in __profd_ relative
Change `CountersPtr` in `__profd_` to a label difference, which is a link-time
constant. On ELF, when linking a shared object, this requires that `__profc_` is
either private or linkonce/linkonce_odr hidden. On COFF, we need D104564 so that
`.quad a-b` (64-bit label difference) can lower to a 32-bit PC-relative relocation.

```
# ELF: R_X86_64_PC64 (PC-relative)
.quad .L__profc_foo-.L__profd_foo

# Mach-O: a pair of 8-byte X86_64_RELOC_UNSIGNED and X86_64_RELOC_SUBTRACTOR
.quad l___profc_foo-l___profd_foo

# COFF: we actually use IMAGE_REL_AMD64_REL32/IMAGE_REL_ARM64_REL32 so
# the high 32-bit value is zero even if .L__profc_foo < .L__profd_foo
# As compensation, we truncate CountersDelta in the header so that
# __llvm_profile_merge_from_buffer and llvm-profdata reader keep working.
.quad .L__profc_foo-.L__profd_foo
```

(Note: link.exe sorts `.lprfc` before `.lprfd` even if the object writer
has `.lprfd` before `.lprfc`, so we cannot work around by reordering
`.lprfc` and `.lprfd`.)

With this change, a stage 2 (`-DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_BUILD_INSTRUMENTED=IR`)
`ld -pie` linked clang is 1.74% smaller due to fewer R_X86_64_RELATIVE relocations.
```
% readelf -r pie | awk '$3~/R.*/{s[$3]++} END {for (k in s) print k, s[k]}'
R_X86_64_JUMP_SLO 331
R_X86_64_TPOFF64 2
R_X86_64_RELATIVE 476059  # was: 607712
R_X86_64_64 2616
R_X86_64_GLOB_DAT 31
```

The absolute function address (used by llvm-profdata to collect indirect call
targets) can be converted to relative as well, but is not done in this patch.

Differential Revision: https://reviews.llvm.org/D104556
2021-07-30 11:52:18 -07:00
Nico Weber f917c5b8d4 Revert test fixups after e9a9c85098 (which reverted a14fc74).
This reverts commit da3ed58b97.
This reverts commit ba1fb0ff8c.
2021-06-04 10:42:25 -04:00
Fangrui Song da3ed58b97 [test] Update more clang/test/Profile tests 2021-06-03 13:43:19 -07:00
Fangrui Song ba1fb0ff8c [test] Update c-linkage-available_externally.c 2021-06-03 13:40:01 -07:00
Thomas Preud'homme 95f448aa86 [PGO, test] Fix typo in FileCheck var
Reviewed By: xur

Differential Revision: https://reviews.llvm.org/D99821
2021-04-03 08:44:46 +01:00
Petr Hosek 8459b8ef39 [Driver] Rename -fprofile-{prefix-map,compilation-dir} to -fcoverage-{prefix-map,compilation-dir}
These flags affect coverage mapping (-fcoverage-mapping), not
-fprofile-[instr-]generate so it makes more sense to use the
-fcoverage-* prefix.

Differential Revision: https://reviews.llvm.org/D97434
2021-02-25 21:40:12 -08:00
Petr Hosek 3275b18f89 [Coverage] Normalize compilation dir as well
This matches debug info behavior.

Differential Revision: https://reviews.llvm.org/D97001
2021-02-19 15:29:03 -08:00
Petr Hosek 5fbd1a333a [Coverage] Store compilation dir separately in coverage mapping
We currently always store absolute filenames in coverage mapping.  This
is problematic for several reasons. It poses a problem for distributed
compilation as source location might vary across machines.  We are also
duplicating the path prefix potentially wasting space.

This change modifies how we store filenames in coverage mapping. Rather
than absolute paths, it stores the compilation directory and file paths
as given to the compiler, either relative or absolute. Later when
reading the coverage mapping information, we recombine relative paths
with the working directory. This approach is similar to handling
ofDW_AT_comp_dir in DWARF.

Finally, we also provide a new option, -fprofile-compilation-dir akin
to -fdebug-compilation-dir which can be used to manually override the
compilation directory which is useful in distributed compilation cases.

Differential Revision: https://reviews.llvm.org/D95753
2021-02-18 14:34:39 -08:00
Petr Hosek fbf8b957fd Revert "[Coverage] Store compilation dir separately in coverage mapping"
This reverts commit 97ec8fa5bb since
the test is failing on some bots.
2021-02-18 12:50:24 -08:00
Petr Hosek 97ec8fa5bb [Coverage] Store compilation dir separately in coverage mapping
We currently always store absolute filenames in coverage mapping.  This
is problematic for several reasons. It poses a problem for distributed
compilation as source location might vary across machines.  We are also
duplicating the path prefix potentially wasting space.

This change modifies how we store filenames in coverage mapping. Rather
than absolute paths, it stores the compilation directory and file paths
as given to the compiler, either relative or absolute. Later when
reading the coverage mapping information, we recombine relative paths
with the working directory. This approach is similar to handling
ofDW_AT_comp_dir in DWARF.

Finally, we also provide a new option, -fprofile-compilation-dir akin
to -fdebug-compilation-dir which can be used to manually override the
compilation directory which is useful in distributed compilation cases.

Differential Revision: https://reviews.llvm.org/D95753
2021-02-18 12:27:42 -08:00
Keith Smiley c3324450b2 [clang] Add -fprofile-prefix-map
This flag allows you to re-write absolute paths in coverage data analogous to -fdebug-prefix-map. This flag is also implied by -ffile-prefix-map.
2021-01-25 10:14:04 -08:00
Jan Svoboda ce8c59e6af Reapply multiple "[clang][cli]" patches
This reverts 7ad666798f and 1876a2914f that reverted:

741978d727 [clang][cli] Port CodeGen option flags to new option parsing system
383778e217 [clang][cli] Port LangOpts option flags to new option parsing system
aec2991d08 [clang][cli] Port LangOpts simple string based options to new option parsing system
95d3cc67ca [clang][cli] Port CodeGenOpts simple string flags to new option parsing system
27b7d64688 [clang][cli] Streamline MarshallingInfoFlag description
70410a2649 [clang][cli] Let denormalizer decide how to render the option based on the option class
63a24816f5 [clang][cli] Implement `getAllArgValues` marshalling

Commit 741978d727 accidentally changed the `Group` attribute of `g[no_]column_info` options from `g_flags_Group` to `g_Group`, which changed the debug info options passed to cc1 by the driver.

Similar change was also present in 383778e217, which accidentally added `Group<f_Group>` to `f[no_]const_strings` and `f[no_]signed_wchar`.

This patch corrects all three accidental changes by replacing `Bool{G,F}Option` with `BoolCC1Option`.
2021-01-06 13:27:19 +01:00
Alan Phipps 2168942117 [Coverage] Fix Profile test failures from commit rG9f2967bcfe2f
Fix test failures with Branch Coverage tests from commit rG9f2967bcfe2f
that failed build on builder clang-x64-windows-msvc while building llvm:
    http://lab.llvm.org:8011/#/builders/123/builds/2162
2021-01-05 14:53:07 -06:00
Alan Phipps 16f3401eae [Coverage] Fix test failures from commit rG9f2967bcfe2f
Fix test failures with Branch Coverage tests from commit rG9f2967bcfe2f
that failed build on builder clang-x64-windows-msvc while building llvm:
    http://lab.llvm.org:8011/#builders/123/builds/2155
2021-01-05 13:35:52 -06:00
Alan Phipps 9f2967bcfe [Coverage] Add support for Branch Coverage in LLVM Source-Based Code Coverage
This is an enhancement to LLVM Source-Based Code Coverage in clang to track how
many times individual branch-generating conditions are taken (evaluate to TRUE)
and not taken (evaluate to FALSE).  Individual conditions may comprise larger
boolean expressions using boolean logical operators.  This functionality is
very similar to what is supported by GCOV except that it is very closely
anchored to the ASTs.

Differential Revision: https://reviews.llvm.org/D84467
2021-01-05 09:51:51 -06:00
Fangrui Song 6b3351792c [test] Add {{.*}} to make tests immune to dso_local/dso_preemptable/(none) differences
For a definition (of most linkage types), dso_local is set for ELF -fno-pic/-fpie
and COFF, but not for Mach-O.  This nuance causes unneeded binary format differences.

This patch replaces (function) `define ` with `define{{.*}} `,
(variable/constant/alias) `= ` with `={{.*}} `, or inserts appropriate `{{.*}} `
if there is an explicit linkage.

* Clang will set dso_local for Mach-O, which is currently implied by TargetMachine.cpp. This will make COFF/Mach-O and executable ELF similar.
* Eventually I hope we can make dso_local the textual LLVM IR default (write explicit "dso_preemptable" when applicable) and -fpic ELF will be similar to everything else. This patch helps move toward that goal.
2020-12-30 20:52:01 -08:00
Nico Weber 7ad666798f Revert 741978d727 and things that landed on top of it.
741978d727 made clang produce output that's 2x as large at least in
sanitizer builds. https://reviews.llvm.org/D83892#2470185 has a
standalone repro.

This reverts the following commits:

Revert "[clang][cli] Port CodeGenOpts simple string flags to new option parsing system"
This reverts commit 95d3cc67ca.

Revert "[clang][cli] Port LangOpts simple string based options to new option parsing system"
This reverts commit aec2991d08.

Revert "[clang][cli] Streamline MarshallingInfoFlag description"
This reverts commit 27b7d64688.

Revert "[clang][cli] Port LangOpts option flags to new option parsing system"
This reverts commit 383778e217.

Revert "[clang][cli] Port CodeGen option flags to new option parsing system"
This reverts commit 741978d727.
2020-12-23 12:52:11 -05:00
Jan Svoboda 95d3cc67ca [clang][cli] Port CodeGenOpts simple string flags to new option parsing system
Depends on D84668

Reviewed By: Bigcheese

Original patch by Daniel Grumberg.

Differential Revision: https://reviews.llvm.org/D84669
2020-12-18 10:28:48 +01:00
CJ Johnson 69cd776e1e [CodeGen] Apply 'nonnull' and 'dereferenceable(N)' to 'this' pointer
arguments.

* Adds 'nonnull' and 'dereferenceable(N)' to 'this' pointer arguments
* Gates 'nonnull' on -f(no-)delete-null-pointer-checks
* Introduces this-nonnull.cpp and microsoft-abi-this-nullable.cpp tests to
  explicitly test the behavior of this change
* Refactors hundreds of over-constrained clang tests to permit these
  attributes, where needed
* Updates Clang12 patch notes mentioning this change

Reviewed-by: rsmith, jdoerfert

Differential Revision: https://reviews.llvm.org/D17993
2020-11-16 17:39:17 -08:00
Roman Lebedev 6861d938e5
Revert "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM"
See discussion in https://bugs.llvm.org/show_bug.cgi?id=45073 / https://reviews.llvm.org/D66324#2334485
the implementation is known-broken for certain inputs,
the bugreport was up for a significant amount of timer,
and there has been no activity to address it.
Therefore, just completely rip out all of misexpect handling.

I suspect, fixing it requires redesigning the internals of MD_misexpect.
Should anyone commit to fixing the implementation problem,
starting from clean slate may be better anyways.

This reverts commit 7bdad08429,
and some of it's follow-ups, that don't stand on their own.
2020-11-14 13:12:38 +03:00
Atmn Patel ac73b73c16 [clang] Add mustprogress and llvm.loop.mustprogress attribute deduction
Since C++11, the C++ standard has a forward progress guarantee
[intro.progress], so all such functions must have the `mustprogress`
requirement. In addition, from C11 and onwards, loops without a non-zero
constant conditional or no conditional are also required to make
progress (C11 6.8.5p6). This patch implements these attribute deductions
so they can be used by the optimization passes.

Differential Revision: https://reviews.llvm.org/D86841
2020-11-04 22:03:14 -05:00
Arthur Eubanks 5c31b8b94f Revert "Use uint64_t for branch weights instead of uint32_t"
This reverts commit 10f2a0d662.

More uint64_t overflows.
2020-10-31 00:25:32 -07:00
Arthur Eubanks 10f2a0d662 Use uint64_t for branch weights instead of uint32_t
CallInst::updateProfWeight() creates branch_weights with i64 instead of i32.
To be more consistent everywhere and remove lots of casts from uint64_t
to uint32_t, use i64 for branch_weights.

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D88609
2020-10-30 10:03:46 -07:00
Nico Weber 2a4e704c92 Revert "Use uint64_t for branch weights instead of uint32_t"
This reverts commit e5766f25c6.
Makes clang assert when building Chromium, see https://crbug.com/1142813
for a repro.
2020-10-27 09:26:21 -04:00
Arthur Eubanks e5766f25c6 Use uint64_t for branch weights instead of uint32_t
CallInst::updateProfWeight() creates branch_weights with i64 instead of i32.
To be more consistent everywhere and remove lots of casts from uint64_t
to uint32_t, use i64 for branch_weights.

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D88609
2020-10-26 20:24:04 -07:00
Richard Smith 552c6c2328 PR44406: Follow behavior of array bound constant folding in more recent versions of GCC.
Old GCC used to aggressively fold VLAs to constant-bound arrays at block
scope in GNU mode. That's non-conforming, and more modern versions of
GCC only do this at file scope. Update Clang to do the same.

Also promote the warning for this from off-by-default to on-by-default
in all cases; more recent versions of GCC likewise warn on this by
default.

This is still slightly more permissive than GCC, as pointed out in
PR44406, as we still fold VLAs to constant arrays in structs, but that
seems justifiable given that we don't support VLA-in-struct (and don't
intend to ever support it), but GCC does.

Differential Revision: https://reviews.llvm.org/D89523
2020-10-16 14:34:35 -07:00
Hiroshi Yamauchi 3d6f53018f [PGO] Include the mem ops into the function hash.
To avoid hash collisions when the only difference is in mem ops.
2020-07-30 09:26:20 -07:00
Hiroshi Yamauchi ae7589e1f1 Revert "[PGO] Include the mem ops into the function hash."
This reverts commit 120e66b341.

Due to a buildbot failure.
2020-07-29 15:04:57 -07:00
Hiroshi Yamauchi 120e66b341 [PGO] Include the mem ops into the function hash.
To avoid hash collisions when the only difference is in mem ops.

Differential Revision: https://reviews.llvm.org/D84782
2020-07-29 13:59:40 -07:00
Rong Xu 50da55a585 [PGO] Supporting code for always instrumenting entry block
This patch includes the supporting code that enables always
instrumenting the function entry block by default.

This patch will NOT the default behavior.

It adds a variant bit in the profile version, adds new directives in
text profile format, and changes llvm-profdata tool accordingly.

This patch is a split of D83024 (https://reviews.llvm.org/D83024)
Many test changes from D83024 are also included.

Differential Revision: https://reviews.llvm.org/D84261
2020-07-22 15:01:53 -07:00
serge-sans-paille 63489c39de Fix version of c-general.profdata.v5 test case
de02a75e39 incorrectly upgraded it to v6
2020-06-10 16:20:20 +02:00
serge-sans-paille de02a75e39 [PGO] Fix computation of function Hash
And bump its version number accordingly.

This is a patched recommit of 7c298c104b

Previous hash implementation was incorrectly passing an uint64_t, that got converted
to an uint8_t, to finalize the hash computation. This led to different functions
having the same hash if they only differ by the remaining statements, which is
incorrect.

Added a new test case that trivially tests that a small function change is
reflected in the hash value.

Not that as this patch fixes the hash computation, it would invalidate all hashes
computed before that patch applies, this is why we bumped the version number.

Update profile data hash entries due to hash function update, except for binary
version, in which case we keep the buggy behavior for backward compatibility.

Differential Revision: https://reviews.llvm.org/D79961
2020-05-27 09:15:21 +02:00
Benjamin Kramer 2b8d6fa0ac Revert "[PGO] Fix computation of function Hash"
This reverts commit 7c298c104b.
Fails make check-clang.

Failing Tests (8):
	Clang :: Profile/c-counter-overflows.c
	Clang :: Profile/c-general.c
	Clang :: Profile/c-unprofiled-blocks.c
	Clang :: Profile/cxx-rangefor.cpp
	Clang :: Profile/cxx-throws.cpp
	Clang :: Profile/misexpect-switch-default.c
	Clang :: Profile/misexpect-switch-nonconst.c
	Clang :: Profile/misexpect-switch.c
2020-05-25 20:14:28 +02:00
serge-sans-paille 7c298c104b [PGO] Fix computation of function Hash
Previous implementation was incorrectly passing an uint64_t, that got converted
to an uint8_t, to finalize the hash computation. This led to different functions
having the same hash if they only differ by the remaining statements, which is
incorrect.

Added a new test case that trivially tests that a small function change is
reflected in the hash value.

Not that as this patch fixes the hash computation, it invalidates all hashes
computed before that patch applies, which could be an issue for large build
system that pre-compute the profile data and let client download them as part of
the build process.

Differential Revision: https://reviews.llvm.org/D79961
2020-05-25 17:17:29 +02:00
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