Commit Graph

4003 Commits

Author SHA1 Message Date
Fangrui Song 6e11ed5205 Fix polly build after 8c2082e1dc 2020-06-25 14:39:08 -07:00
Christopher Tetreault b82a95f8bc [SVE] Eliminate calls to default-false VectorType::get() from polly
Reviewers: bollu, efriedma, david-arm, fpetrogalli, gchatelet

Reviewed By: fpetrogalli

Subscribers: tschuett, rkruppe, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80341
2020-05-29 10:04:06 -07:00
Eli Friedman f26bdb539e Make Value::getPointerAlignment() return an Align, not a MaybeAlign.
If we don't know anything about the alignment of a pointer, Align(1) is
still correct: all pointers are at least 1-byte aligned.

Included in this patch is a bugfix for an issue discovered during this
cleanup: pointers with "dereferenceable" attributes/metadata were
assumed to be aligned according to the type of the pointer.  This
wasn't intentional, as far as I can tell, so Loads.cpp was fixed to
stop making this assumption. Frontends may need to be updated.  I
updated clang's handling of C++ references, and added a release note for
this.

Differential Revision: https://reviews.llvm.org/D80072
2020-05-20 16:37:20 -07:00
Florian Hahn 7004a621a0 [Polly] Update ScalarEvolutionExpander.h include. 2020-05-20 12:21:32 +01:00
Eli Friedman 4f04db4b54 AllocaInst should store Align instead of MaybeAlign.
Along the lines of D77454 and D79968.  Unlike loads and stores, the
default alignment is getPrefTypeAlign, to match the existing handling in
various places, including SelectionDAG and InstCombine.

Differential Revision: https://reviews.llvm.org/D80044
2020-05-16 14:53:16 -07:00
Eli Friedman 1a6e4a2cf6 Fix polly tests after D79968. 2020-05-15 15:15:09 -07:00
Eli Friedman 4532a50899 Infer alignment of unmarked loads in IR/bitcode parsing.
For IR generated by a compiler, this is really simple: you just take the
datalayout from the beginning of the file, and apply it to all the IR
later in the file. For optimization testcases that don't care about the
datalayout, this is also really simple: we just use the default
datalayout.

The complexity here comes from the fact that some LLVM tools allow
overriding the datalayout: some tools have an explicit flag for this,
some tools will infer a datalayout based on the code generation target.
Supporting this properly required plumbing through a bunch of new
machinery: we want to allow overriding the datalayout after the
datalayout is parsed from the file, but before we use any information
from it. Therefore, IR/bitcode parsing now has a callback to allow tools
to compute the datalayout at the appropriate time.

Not sure if I covered all the LLVM tools that want to use the callback.
(clang? lli? Misc IR manipulation tools like llvm-link?). But this is at
least enough for all the LLVM regression tests, and IR without a
datalayout is not something frontends should generate.

This change had some sort of weird effects for certain CodeGen
regression tests: if the datalayout is overridden with a datalayout with
a different program or stack address space, we now parse IR based on the
overridden datalayout, instead of the one written in the file (or the
default one, if none is specified). This broke a few AVR tests, and one
AMDGPU test.

Outside the CodeGen tests I mentioned, the test changes are all just
fixing CHECK lines and moving around datalayout lines in weird places.

Differential Revision: https://reviews.llvm.org/D78403
2020-05-14 13:03:50 -07:00
serge-sans-paille 8ceee08de1 Make Polly tests dependencies explicit
Due to libPolly now using the component infrastructure, it no longer carries all
dependencies as it used to do.

Differential Revision: https://reviews.llvm.org/D79295
2020-05-04 08:06:39 +02:00
serge-sans-paille e849e7a700 Use components instead of libraries in Polly linkage step
As a side effect, this tests (and fix a bug) in the compiler extension handling
of components.

Differential Revision: https://reviews.llvm.org/D78358
2020-04-28 09:44:10 +02:00
Michael Kruse 1ef55ac96e [Polly] Fix long loop due to unsigned warparound.
After the update to ISL to isl-0.22.1-87-gfee05a13 and its change of
isl_*_dim returning -1 instead of 0, the -1 got wrapped-around to
UINT_MAX because Polly often uses 'unsigned' type to represent
dimensions, as ISL did before this patch. This may happen in normal
executions after an out-of-quota.

Fix by catching the error-case earlier.
2020-04-27 12:15:56 -05:00
Simon Pilgrim 39f6f29613 [polly] Don't include PassSupport.h directly - include via Pass.h
Missed this in D78815
2020-04-26 15:51:32 +01:00
Eli Friedman 9b9454af8a Require "target datalayout" to be at the beginning of an IR file.
This will allow us to use the datalayout to disambiguate other
constructs in IR, like load alignment. Split off from D78403.

Differential Revision: https://reviews.llvm.org/D78413
2020-04-20 11:55:49 -07:00
Eli Friedman 4623c2ffa4 Fix interaction of static plugins with -DLLVM_LINK_LLVM_DYLIB=ON.
We should link static plugins into libLLVM.so; they shouldn't depend on
libLLVM.so.

Fixes https://bugs.llvm.org/show_bug.cgi?id=45571

Differential Revision: https://reviews.llvm.org/D78332
2020-04-17 11:49:05 -07:00
Josh Stone 5a0d8c31a3 [NFC] correct "thier" to "their" 2020-04-15 14:38:52 -07:00
Eli Friedman 89e0662dee Make IRBuilder automatically set alignment on load/store/alloca.
This is equivalent in terms of LLVM IR semantics, but we want to
transition away from using MaybeAlign to represent the alignment of
these instructions.

Differential Revision: https://reviews.llvm.org/D77984
2020-04-13 13:43:14 -07:00
Eli Friedman 3f13ee8a00 [NFC] Modernize misc. uses of Align/MaybeAlign APIs.
Use the current getAlign() APIs where it makes sense, and use Align
instead of MaybeAlign when we know the value is non-zero.
2020-04-06 17:53:04 -07:00
Kirill Naumov 3f995ce8b5 [CFGPrinter][CallPrinter][polly] Adding distinct structure for CFGDOTInfo
The patch introduces the system to distinctively store the information
needed for the Control Flow Graph as well as the instrumentary needed for
the follow-up changes: BlockFrequencyInfo and BranchProbabilityInfo.
The patch is a part of sequence of three patches, related to graphs Heat Coloring.

Reviewers: rcorcs, apilipenko, davidxl, sfertile, fedor.sergeev, eraman, bollu

Differential Revision: https://reviews.llvm.org/D76820
2020-04-06 17:42:54 +00:00
Michael Kruse 4dded1a7cb [Polly] Add -polly-isl-arg command line option.
The option is passed as argv to ISL's command line option parser.

Polly's own own command line options take precedence over options passed
as `-polly-isl-arg`. For instance,
`-polly-isl-arg=--schedule-outer-coincidence` will be ignored in favor
of `-polly-opt-outer-coincidence`.

Reviewed By: grosser

Differential Revision: https://reviews.llvm.org/D77303
2020-04-06 08:56:57 -05:00
Eli Friedman 3e5d671c19 [polly][opaque pointers] Remove use of deprecated APIs.
(See also D76269.)
2020-04-03 18:00:33 -07:00
Sylvestre Ledru 72fd1033ea Doc: Links should use https 2020-03-22 22:49:33 +01:00
Michael Kruse 0e93f3b0a0 [Polly] Replace use of std::stringstream. NFC.
Use of std::-style (io)streams is discouraged in the LLVM coding style
(https://llvm.org/docs/CodingStandards.html#include-iostream-is-forbidden).
Replace with a use of llvm::Twine (which uses llvm::raw_ostream behind
the scenes).
2020-03-09 11:35:34 -05:00
Eli Friedman 888b12b270 [polly] Don't count scops in a global variable.
This can cause issues with thread safety.

Differential Revision: https://reviews.llvm.org/D75089
2020-02-24 17:12:08 -08:00
Shoaib Meenai e34ddc09f4 [arcconfig] Delete subproject arcconfigs
From https://secure.phabricator.com/book/phabricator/article/arcanist_new_project/:

> An .arcconfig file is a JSON file which you check into your project's root.

I've done some experimentation, and it looks like the subproject
.arcconfigs just get ignored, as the documentation says. Given that
we're fully on the monorepo now, it's safe to remove them.

Differential Revision: https://reviews.llvm.org/D74996
2020-02-24 16:20:36 -08:00
Bardia Mahjour cf9dae122e [NFC] [DA] Refactoring getIndexExpressionsFromGEP
Summary:
This patch moves the getIndexExpressionsFromGEP function from polly
into ScalarEvolution so that both polly and DependenceAnalysis can
use it for the purpose of subscript delinearization when the array
sizes are not parametric.

Authored By: bmahjour

Reviewer: Meinersbur, sebpop, fhahn, dmgreen, grosser, etiotto, bollu

Reviewed By: Meinersbur

Subscribers: hiraditya, arphaman, Whitney, ppc-slack, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73995
2020-02-24 17:32:30 -05:00
Michael Kruse 6369b9bf31 [CMake] Default to static linking for subprojects.
Pass plugins introduced in D61446 do not support dynamic linking on
Windows, hence the option LLVM_${name_upper}_LINK_INTO_TOOLS can only
work being set to "ON". Currently, it defaults to "OFF" such that such
plugins are inoperable by default on Windows. Change the default for
subprojects to follow LLVM_ENABLE_PROJECTS.

Reviewed By: serge-sans-paille, MaskRay

Differential Revision: https://reviews.llvm.org/D72372
2020-02-24 11:54:08 -06:00
Michael Kruse 612c4bf09e [Polly] Run polly-update-format after commit 55cfb1. NFC. 2020-02-17 15:57:06 -06:00
Nikita Popov 3eaa53e805 Reapply "[IRBuilder] Virtualize IRBuilder"
Relative to the original commit, this fixes some warnings,
and is based on the deletion of the IRBuilder copy constructor
in D74693. The automatic copy constructor would no longer be
safe.

-----

Related llvm-dev thread:
http://lists.llvm.org/pipermail/llvm-dev/2020-February/138951.html

This patch moves the IRBuilder from templating over the constant
folder and inserter towards making both of these virtual.
There are a couple of motivations for this:

1. It's not possible to share code between use-sites that use
different IRBuilder folders/inserters (short of templating the code
and moving it into headers).
2. Methods currently defined on IRBuilderBase (which is not templated)
do not use the custom inserter, resulting in subtle bugs (e.g.
incorrect InstCombine worklist management). It would be possible to
move those into the templated IRBuilder, but...
3. The vast majority of the IRBuilder implementation has to live
in the header, because it depends on the template arguments.
4. We have many unnecessary dependencies on IRBuilder.h,
because it is not easy to forward-declare. (Significant parts of
the backend depend on it via TargetLowering.h, for example.)

This patch addresses the issue by making the following changes:

* IRBuilderDefaultInserter::InsertHelper becomes virtual.
  IRBuilderBase accepts a reference to it.
* IRBuilderFolder is introduced as a virtual base class. It is
 implemented by ConstantFolder (default), NoFolder and TargetFolder.
  IRBuilderBase has a reference to this as well.
* All the logic is moved from IRBuilder to IRBuilderBase. This means
  that methods can in the future replace their IRBuilder<> & uses
  (or other specific IRBuilder types) with IRBuilderBase & and thus
  be usable with different IRBuilders.
* The IRBuilder class is now a thin wrapper around IRBuilderBase.
  Essentially it only stores the folder and inserter and takes care
  of constructing the base builder.

What this patch doesn't do, but should be simple followups after this change:

* Fixing use of the inserter for creation methods originally defined
  on IRBuilderBase.
* Replacing IRBuilder<> uses in arguments with IRBuilderBase, where useful.
* Moving code from the IRBuilder header to the source file.

From the user perspective, these changes should be mostly transparent:
The only thing that consumers using a custom inserted may need to do is
inherit from IRBuilderDefaultInserter publicly and mark their InsertHelper
as public.

Differential Revision: https://reviews.llvm.org/D73835
2020-02-17 19:04:11 +01:00
Nikita Popov 55cfb1fb50 [Polly] Fix build after IRBuilder changes
Simply dropping the createPollyIRBuilder() function here, because
it doesn't do much. Also directly initialize Expander in
ScopExpander instead of going through the copy-constructor.
2020-02-17 19:02:50 +01:00
Nikita Popov af480e8c63 Revert "[IRBuilder] Virtualize IRBuilder"
This reverts commit 0765d3824d.
This reverts commit 1b04866a3d.

Relevant looking crashes observed on:
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win
2020-02-16 17:01:10 +01:00
Nikita Popov 1b04866a3d [IRBuilder] Try to fix warnings
Try to fix -Wnon-virtual-dtor warnings that cause build failure
on clang-pcc64le-rhel.
2020-02-16 15:32:11 +01:00
Nikita Popov 0765d3824d [IRBuilder] Virtualize IRBuilder
Related llvm-dev thread:
http://lists.llvm.org/pipermail/llvm-dev/2020-February/138951.html

This patch moves the IRBuilder from templating over the constant
folder and inserter towards making both of these virtual.
There are a couple of motivations for this:

1. It's not possible to share code between use-sites that use
different IRBuilder folders/inserters (short of templating the code
and moving it into headers).
2. Methods currently defined on IRBuilderBase (which is not templated)
do not use the custom inserter, resulting in subtle bugs (e.g.
incorrect InstCombine worklist management). It would be possible to
move those into the templated IRBuilder, but...
3. The vast majority of the IRBuilder implementation has to live
in the header, because it depends on the template arguments.
4. We have many unnecessary dependencies on IRBuilder.h,
because it is not easy to forward-declare. (Significant parts of
the backend depend on it via TargetLowering.h, for example.)

This patch addresses the issue by making the following changes:

* IRBuilderDefaultInserter::InsertHelper becomes virtual.
  IRBuilderBase accepts a reference to it.
* IRBuilderFolder is introduced as a virtual base class. It is
 implemented by ConstantFolder (default), NoFolder and TargetFolder.
  IRBuilderBase has a reference to this as well.
* All the logic is moved from IRBuilder to IRBuilderBase. This means
  that methods can in the future replace their IRBuilder<> & uses
  (or other specific IRBuilder types) with IRBuilderBase & and thus
  be usable with different IRBuilders.
* The IRBuilder class is now a thin wrapper around IRBuilderBase.
  Essentially it only stores the folder and inserter and takes care
  of constructing the base builder.

What this patch doesn't do, but should be simple followups after this change:

* Fixing use of the inserter for creation methods originally defined
  on IRBuilderBase.
* Replacing IRBuilder<> uses in arguments with IRBuilderBase, where useful.
* Moving code from the IRBuilder header to the source file.

From the user perspective, these changes should be mostly transparent:
The only thing that consumers using a custom inserted may need to do is
inherit from IRBuilderDefaultInserter publicly and mark their InsertHelper
as public.

Differential Revision: https://reviews.llvm.org/D73835
2020-02-16 13:48:55 +01:00
Yuanfang Chen 4ad7685258 Revert "Revert "Reland "[Support] make report_fatal_error `abort` instead of `exit`"""
This reverts commit 80a34ae311 with fixes.

Previously, since bots turning on EXPENSIVE_CHECKS are essentially turning on
MachineVerifierPass by default on X86 and the fact that
inline-asm-avx-v-constraint-32bit.ll and inline-asm-avx512vl-v-constraint-32bit.ll
are not expected to generate functioning machine code, this would go
down to `report_fatal_error` in MachineVerifierPass. Here passing
`-verify-machineinstrs=0` to make the intent explicit.
2020-02-13 10:16:06 -08:00
Yuanfang Chen 17122ec10a Revert "Revert "Revert "Reland "[Support] make report_fatal_error `abort` instead of `exit`""""
This reverts commit bb51d24330.
2020-02-13 10:08:05 -08:00
Yuanfang Chen bb51d24330 Revert "Revert "Reland "[Support] make report_fatal_error `abort` instead of `exit`"""
This reverts commit 80a34ae311 with fixes.

On bots llvm-clang-x86_64-expensive-checks-ubuntu and
llvm-clang-x86_64-expensive-checks-debian only,
llc returns 0 for these two tests unexpectedly. I tweaked the RUN line a little
bit in the hope that LIT is the culprit since this change is not in the
codepath these tests are testing.
llvm\test\CodeGen\X86\inline-asm-avx-v-constraint-32bit.ll
llvm\test\CodeGen\X86\inline-asm-avx512vl-v-constraint-32bit.ll
2020-02-13 10:02:53 -08:00
Huihui Zhang aedda89f65 [NFC] Fix warning: comparison of integers of different signs.
../polly/lib/Transform/ScheduleOptimizer.cpp:812:54: warning: comparison of integers of different signs: 'isl_size' (aka 'int') and 'const unsigned int' [-Wsign-compare]
         isl_schedule_node_band_n_member(Node.get()) >
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
2020-02-11 14:46:09 -08:00
Michael Halkenhäuser 1e0be76e98 [Polly] LLVM OpenMP Backend -- Fix "static chunked" scheduling.
Static chunked OpenMP scheduling has not been treated correctly.
This patch fixes the problem that threads would not process their
(work-)chunks as intended.

Differential Revision: https://reviews.llvm.org/D61081
2020-02-11 12:51:35 -06:00
Michael Kruse 86500b3f1c [Polly][Docs] Fix wrong claim about optimization levels.
Thanks Justin Paston-Cooper for the report.
2020-02-10 20:14:40 -06:00
Michael Kruse d0240257cd [Polly] Silence mixed signed/unsigned comparison warnings. NFC.
ISL changed some return types from unsigned to
isl_size (typedef of int), which results in such warnings.
2020-02-10 19:03:08 -06:00
Michael Kruse e8227804ac [Polly] Update ISL to isl-0.22.1-87-gfee05a13.
The primary motivation is to fix an assertion failure in
isl_basic_map_alloc_equality:

    isl_assert(ctx, room_for_con(bmap, 1), return -1);

Although the assertion does not occur anymore, I could not identify
which of ISL's commits fixed it.

Compared to the previous ISL version, Polly requires some changes for this update

 * Since ISL commit
   20d3574 "perform parameter alignment by modifying both arguments to function"
   isl_*_gist_* and similar functions do not always align the paramter
   list anymore. This caused the parameter lists in JScop files to
   become out-of-sync. Since many regression tests use JScop files with
   a fixed parameter list and order, we explicitly call align_params to
   ensure a predictable parameter list.

 * ISL changed some return types to isl_size, a typedef of (signed) int.
   This caused some issues where the return type was unsigned int before:
   - No overload for std::max(unsigned,isl_size)
   - It cause additional 'mixed signed/unsigned comparison' warnings.
     Since they do not break compilation, and sizes larger than 2^31
     were never supported, I am going to fix it separately.

 * With the change to isl_size, commit
   57d547 "isl_*_list_size: return isl_size"
   also changed the return value in case of an error from 0 to -1. This
   caused undefined looping over isl_iterator since the 'end iterator'
   got index -1, never reached from the 'begin iterator' with index 0.

 * Some internal changes in ISL caused the number of operations to
   increase when determining access ranges to determine aliasing
   overlaps. In one test, this caused exceeding the default limit of
   800000. The operations-limit was disabled for this test.
2020-02-10 19:03:08 -06:00
Michael Kruse 84c934a5cb Silence compiler warning. NFC.
The idiom

    for (auto i = n - n; i < n; i += 1)

was intended to automatically derive the type of i from n
(signed/unsigned int) and avoid the 'mixed signed/unsigned comparison'
warning. However, almost-always-auto was never used in the LLVM coding
style (although we used it in Polly for some time) and I did never
intended to use this idiom upstream.

PVS Studio may warns about this idiom as 'warning: both sides of
operator are equivalent [misc-redundant-expression]'.

Remove the use of auto and directly use unsigned.

Also see http://llvm.org/PR44768
2020-02-10 11:38:22 -06:00
Michael Kruse 1a53b732e6 Compile-fix after StringRef's conversion operator has been made explicit.
Commit 777180a "[ADT] Make StringRef's std::string conversion operator explicit"
caused Polly's GPU code generator to not compile anymore. The rest of
Polly has already been fixed in commit
0257a9 "Fix polly build after StringRef change."
2020-02-05 22:28:05 -06:00
Krzysztof Parzyszek d4c8230a0f [Polly] Fix compilation after 105642af5eef: include PassManagerImpl.h 2020-02-04 08:22:22 -06:00
Eli Friedman 0257a9218b Fix polly build after StringRef change. 2020-01-28 19:44:20 -08:00
Eli Friedman 2f6b9edfa8 [AliasAnalysis] Add missing FMRB_* enums.
Previously, the enums didn't account for all the possible cases, which
could cause misleading results (particularly for a "switch" on
FunctionModRefBehavior).

Fixes regression in polly from recent patch to add writeonly to memset.

While I'm here, also fix a few dubious uses of the FMRB_* enum values.

Differential Revision: https://reviews.llvm.org/D73154
2020-01-28 15:47:08 -08:00
Guillaume Chatelet 07c9d53266 [Alignment][NFC] Use Align with CreateAlignedLoad
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

Reviewers: courbet, bollu

Subscribers: hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D73449
2020-01-27 10:58:36 +01:00
Guillaume Chatelet 805c157e8a [Alignment][NFC] Deprecate Align::None()
Summary:
This is a follow up on https://reviews.llvm.org/D71473#inline-647262.
There's a caveat here that `Align(1)` relies on the compiler understanding of `Log2_64` implementation to produce good code. One could use `Align()` as a replacement but I believe it is less clear that the alignment is one in that case.

Reviewers: xbolva00, courbet, bollu

Subscribers: arsenm, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, hiraditya, kbarton, jrtc27, atanasyan, jsji, Jim, kerbowa, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D73099
2020-01-24 12:53:58 +01:00
Dominik Adamski 7154413567 [NFC][ScopBuilder] Move RecordedAssumptions vector to ScopBuilder
Scope of changes:

1) Moved RecordedAssumptions vector to ScopBuilder. RecordedAssumptions are used only for Scop constructions.
2) Moved definition of RecordedAssumptionsTy to ScopHelper. It is required both by ScopBuilder and SCEVAffinator.
3) Add new function recordAssumption to ScopHelper. One of its argument is a reference to RecordedAssumption vector. This function is used by ScopBuilder and SCEVAffinator.
4) All RecordedAssumptions are created by ScopBuilder. isl::pw_aff
objects for corresponding SCEVs are created inside ScopBuilder. Scop
functions do not record any assumptions. Scop can use isl::pw_aff
objects which were created by ScopBuilder.
5) Removed functions for handling RecordedAssumptions from Scop class.
6) Removed constness from getScopArrayInfo functions.
7) Replaced SCEVVisitor struct from SCEVAffinator with taylored version, which allow to pass pointer to RecordedAssumptions as function argument.

Differential Revision: https://reviews.llvm.org/D68056
2020-01-24 00:09:01 +01:00
Guillaume Chatelet 59f95222d4 [Alignment][NFC] Use Align with CreateAlignedStore
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

Reviewers: courbet, bollu

Subscribers: arsenm, jvesely, nhaehnle, hiraditya, kerbowa, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D73274
2020-01-23 17:34:32 +01:00
Eli Friedman d9e6196312 [polly] XFAIL memset_null.ll.
I'm working on a patch, but not sure how long it'll take.
2020-01-21 17:29:44 -08:00
David Blaikie 65eb74e94b PointerLikeTypeTraits: Standardize NumLowBitsAvailable on static constexpr rather than anonymous enum
This is (more?) usable by GDB pretty printers and seems nicer to write.

There's one tricky caveat that in C++14 (LLVM's codebase today) the
static constexpr member declaration is not a definition - so odr use of
this constant requires an out of line definition, which won't be
provided (that'd make all these trait classes more annoyidng/expensive
to maintain). But the use of this constant in the library implementation
is/should always be in a non-odr context - only two unit tests needed to
be touched to cope with this/avoid odr using these constants.

Based on/expanded from D72590 by Christian Sigg.
2020-01-16 15:30:50 -08:00