Commit Graph

8593 Commits

Author SHA1 Message Date
Hans Wennborg 0a5dd06718 Revert "[ObjC][ARC] Use operand bundle 'clang.arc.attachedcall' instead of explicitly emitting retainRV or claimRV calls in the IR"
This caused miscompiles of Chromium tests for iOS due clobbering of live
registers. See discussion on the code review for details.

> Background:
>
> This fixes a longstanding problem where llvm breaks ARC's autorelease
> optimization (see the link below) by separating calls from the marker
> instructions or retainRV/claimRV calls. The backend changes are in
> https://reviews.llvm.org/D92569.
>
> https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue
>
> What this patch does to fix the problem:
>
> - The front-end adds operand bundle "clang.arc.attachedcall" to calls,
>   which indicates the call is implicitly followed by a marker
>   instruction and an implicit retainRV/claimRV call that consumes the
>   call result. In addition, it emits a call to
>   @llvm.objc.clang.arc.noop.use, which consumes the call result, to
>   prevent the middle-end passes from changing the return type of the
>   called function. This is currently done only when the target is arm64
>   and the optimization level is higher than -O0.
>
> - ARC optimizer temporarily emits retainRV/claimRV calls after the calls
>   with the operand bundle in the IR and removes the inserted calls after
>   processing the function.
>
> - ARC contract pass emits retainRV/claimRV calls after the call with the
>   operand bundle. It doesn't remove the operand bundle on the call since
>   the backend needs it to emit the marker instruction. The retainRV and
>   claimRV calls are emitted late in the pipeline to prevent optimization
>   passes from transforming the IR in a way that makes it harder for the
>   ARC middle-end passes to figure out the def-use relationship between
>   the call and the retainRV/claimRV calls (which is the cause of
>   PR31925).
>
> - The function inliner removes an autoreleaseRV call in the callee if
>   nothing in the callee prevents it from being paired up with the
>   retainRV/claimRV call in the caller. It then inserts a release call if
>   claimRV is attached to the call since autoreleaseRV+claimRV is
>   equivalent to a release. If it cannot find an autoreleaseRV call, it
>   tries to transfer the operand bundle to a function call in the callee.
>   This is important since the ARC optimizer can remove the autoreleaseRV
>   returning the callee result, which makes it impossible to pair it up
>   with the retainRV/claimRV call in the caller. If that fails, it simply
>   emits a retain call in the IR if retainRV is attached to the call and
>   does nothing if claimRV is attached to it.
>
> - SCCP refrains from replacing the return value of a call with a
>   constant value if the call has the operand bundle. This ensures the
>   call always has at least one user (the call to
>   @llvm.objc.clang.arc.noop.use).
>
> - This patch also fixes a bug in replaceUsesOfNonProtoConstant where
>   multiple operand bundles of the same kind were being added to a call.
>
> Future work:
>
> - Use the operand bundle on x86-64.
>
> - Fix the auto upgrader to convert call+retainRV/claimRV pairs into
>   calls with the operand bundles.
>
> rdar://71443534
>
> Differential Revision: https://reviews.llvm.org/D92808

This reverts commit ed4718eccb.
2021-03-03 15:51:40 +01:00
Stefan Gränitz 403bdd5006 [docs][JITLink] Fix a typo (NFC) 2021-03-02 15:07:36 +01:00
Tony Tye 2da13f1246 [NFC][AMDGPU] Document the AMDGPU target feature defaults
Document the default for the XNACK and SRAMECC target features for code object V2-V3 and V4.

Reviewed By: kzhuravl

Differential Revision: https://reviews.llvm.org/D97598
2021-02-27 18:28:15 +00:00
Kazu Hirata e8fa9014cc [llvm] Fix typos in documentation (NFC) 2021-02-27 10:09:23 -08:00
Arthur Eubanks 016f0ee686 [docs] Add documentation on using the new pass manager
And clarify in the "writing a pass" docs that both the legacy and new
PMs are being used for the codegen/optimization pipelines.

Reviewed By: ychen, asbirlea

Differential Revision: https://reviews.llvm.org/D97515
2021-02-26 15:28:19 -08:00
Stefan Gränitz 57f8f23757 [docs][JITLink] Few typo fixes in JITLink design/API doc 2021-02-26 12:56:42 +01:00
Nico Weber 03b7bc0ba1 [arm builtin crosscompile docs] add COMPILER_RT_BUILD_MEMPROF=OFF
Reported by artok on irc, thanks!
2021-02-25 10:44:52 -05:00
Nico Weber b4f8daa5ec [arm builtin crosscompile docs] alphabetize flags, no behavior change 2021-02-25 10:44:16 -05:00
Lang Hames 93c8246952 [docs][JITLink] Reintroduce JITLink design/API doc with fixes and improvements.
This document was originally introduced in ab4648504b, and was reverted in
912bc4980e while I investigated a number of shpinx bot errors. This commit
reintroduces the document with fixes for those errors, as well as some
improvements to the wording and formatting.
2021-02-25 15:27:59 +11:00
Joel E. Denny 2a5aa81739 [lit] Add --ignore-fail
For some build configurations, `check-all` calls lit multiple times to
run multiple lit test suites.  Most recently, I've found this to be
true when configuring openmp as part of `LLVM_ENABLE_RUNTIMES`, but
this is not the first time.

If one test suite fails, none of the remaining test suites run, so you
cannot determine if your patch has broken them.  It can then be
frustrating to try to determine which `check-` targets will run the
remaining tests without getting stuck on the failing tests.

When such cases arise, it is probably best to adjust the cmake
configuration for `check-all` to run all test suites as part of one
lit invocation.  Because that fix will likely not be implemented and
land immediately, this patch introduces `--ignore-fail` to serve as a
workaround for developers trying to see test results until it does
land:

```
$ LIT_OPTS=--ignore-fail ninja check-all
```

One problem with `--ignore-fail` is that it makes it challenging to
detect test failures in a script, perhaps in CI.  This problem should
serve as motivation to actually fix the cmake configuration instead of
continuing to use `--ignore-fail` indefinitely.

Reviewed By: jhenderson, thopre

Differential Revision: https://reviews.llvm.org/D96371
2021-02-24 13:10:27 -05:00
Lang Hames 912bc4980e [docs][JITLink] Remove the JITLink doc for now.
I'll reinstate and continue investigation tomorrow.
2021-02-24 22:32:18 +11:00
Lang Hames 038a09120b [docs][JITLink] Yet more experiments to try to understand sphinx error. 2021-02-24 22:22:48 +11:00
Lang Hames 3fbe630e03 [docs][JITLink] More experiments to try to understand sphinx error. 2021-02-24 22:22:47 +11:00
Lang Hames a4f9c0f562 [docs][JITLink] Make ``ObjectLinkingLayer`` not a paragraph start.
More experiments as I try to placate sphinx.
2021-02-24 22:04:14 +11:00
Lang Hames e2db0d2fa6 [docs][JITLink] Return to `` for inline literals.
Also awkwardly reformat text to test whether the error is occurring
on the line with the '::', or the previous one.
2021-02-24 21:55:49 +11:00
Lang Hames 731a2bcaf7 [docs][JITLink] Try explicit literal blocks for monospace list elements. 2021-02-24 21:50:27 +11:00
Lang Hames d91cfcebbd [docs][JITLink] More attempted fixes for formatting issues in the JITLink doc.
Try using the literal domain for `ObjectLinkingLayer::Plugin` and literal
blocks for multi-line method names.
2021-02-24 21:41:27 +11:00
Lang Hames a5e15c7706 [docs][JITLink] Sphinx does not like '::' in monotype. Try using a
cpp domain expr instead.
2021-02-24 21:23:10 +11:00
Lang Hames ab4648504b [docs][JITLink] Add a JITLink design and API document. 2021-02-24 21:04:35 +11:00
xgupta 9a9d56eb3e [Docs] Mention clone depth feature of git in LLVM getting started
The current size of the llvm-project repository exceeds 1 GB. A shallow clone can save a lot of space and time. Some developers might not aware of this feature.

Reviewed By: awarzynski

Differential Revision: https://reviews.llvm.org/D97118
2021-02-24 10:56:10 +05:30
Lang Hames 479db97a34 Revert "[docs][ORC] Fix section title and reference."
This reverts commit 6e1affe71c, which caused an
error on the Sphinx doc bot.
2021-02-24 07:27:39 +11:00
Lang Hames 6e1affe71c [docs][ORC] Fix section title and reference. 2021-02-23 17:38:51 +11:00
Sanjay Patel b02bc0224a [LangRef] fix typo in assume bundle description; NFC 2021-02-22 09:30:49 -05:00
Dmitry Preobrazhensky 4813518092 [AMDGPU][MC] Corrected bound_ctrl for compatibility with sp3
Enabled "bound_ctrl:1" and disabled "bound_ctrl:-1" syntax.
Corrected printer to output "bound_ctrl:1" instead of "bound_ctrl:0".
See bug 35397 for detailed issue description.

Differential Revision: https://reviews.llvm.org/D97048
2021-02-22 14:59:40 +03:00
David Zarzycki 45d058e56d [lit] Add --xfail and --filter-out (inverse of --filter)
In semi-automated environments,  XFAILing or filtering out known regressions without actually committing changes or temporarily modifying the test suite can be quite useful.

Reviewed By: yln

Differential Revision: https://reviews.llvm.org/D96662
2021-02-20 05:43:29 -05:00
Djordje Todorovic 0d82980296 [docs] Fix the GlobalISel/GenericOpcode.rst
This couses docs build to fail.
Introduced with D96890.
2021-02-19 10:31:31 +01:00
Djordje Todorovic 1a2b3536ef Reland "[Debugify] Make the debugify aware of the original (-g) Debug Info"
As discussed on the RFC [0], I am sharing the set of patches that
    enables checking of original Debug Info metadata preservation in
    optimizations. The proof-of-concept/proposal can be found at [1].

    The implementation from the [1] was full of duplicated code,
    so this set of patches tries to merge this approach into the existing
    debugify utility.

    For example, the utility pass in the original-debuginfo-check
    mode could be invoked as follows:

      $ opt -verify-debuginfo-preserve -pass-to-test sample.ll

    Since this is very initial stage of the implementation,
    there is a space for improvements such as:
      - Add support for the new pass manager
      - Add support for metadata other than DILocations and DISubprograms

    [0] https://groups.google.com/forum/#!msg/llvm-dev/QOyF-38YPlE/G213uiuwCAAJ
    [1] https://github.com/djolertrk/llvm-di-checker

    Differential Revision: https://reviews.llvm.org/D82545

The test that was failing is now forced to use the old PM.
2021-02-18 23:29:22 -08:00
Konstantin Zhuravlyov 71d1f785a5 AMDGPU/ELF: Sort MACHs by value and add missing reserved MACHs
- Sort MACHs by its value
  - Add missing reserved MACHs
    - EF_AMDGPU_MACH_AMDGCN_RESERVED_0X3D
    - EF_AMDGPU_MACH_AMDGCN_RESERVED_0X3E

Differential Revision: https://reviews.llvm.org/D97010
2021-02-18 20:46:27 -05:00
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
Paul C. Anagnostopoulos 49d663d546 Revert "[TableGen] Improve algorithms for processing template arguments"
This reverts commit e589207d5aaee6cbf1d7c7de8867a17727d14aca.
2021-02-18 09:26:26 -05:00
Paul C. Anagnostopoulos d248cce44e [TableGen] Improve algorithms for processing template arguments
Rework template argument checking so that all arguments are type-checked
and cast if necessary.

Add a test.

Differential Revision: https://reviews.llvm.org/D96416
2021-02-18 09:15:26 -05:00
Djordje Todorovic c1e23894fc Revert "[Debugify] Make the debugify aware of the original (-g) Debug Info"
This reverts rG8ee7c7e02953.
One test is failing, I'll reland this as soon as possible.
2021-02-18 02:04:27 -08:00
Djordje Todorovic 8ee7c7e029 [Debugify] Make the debugify aware of the original (-g) Debug Info
As discussed on the RFC [0], I am sharing the set of patches that
enables checking of original Debug Info metadata preservation in
optimizations. The proof-of-concept/proposal can be found at [1].

The implementation from the [1] was full of duplicated code,
so this set of patches tries to merge this approach into the existing
debugify utility.

For example, the utility pass in the original-debuginfo-check
mode could be invoked as follows:

  $ opt -verify-debuginfo-preserve -pass-to-test sample.ll

Since this is very initial stage of the implementation,
there is a space for improvements such as:
  - Add support for the new pass manager
  - Add support for metadata other than DILocations and DISubprograms

[0] https://groups.google.com/forum/#!msg/llvm-dev/QOyF-38YPlE/G213uiuwCAAJ
[1] https://github.com/djolertrk/llvm-di-checker

Differential Revision: https://reviews.llvm.org/D82545
2021-02-18 01:52:16 -08:00
Stanislav Mekhanoshin a8d9d50762 [AMDGPU] gfx90a support
Differential Revision: https://reviews.llvm.org/D96906
2021-02-17 16:01:32 -08:00
Jessica Paquette 60aa646441 [GlobalISel] Add G_ASSERT_SEXT
This adds a G_ASSERT_SEXT opcode, similar to G_ASSERT_ZEXT. This instruction
signifies that an operation was already sign extended from a smaller type.

This is useful for functions with sign-extended parameters.

E.g.

```
define void @foo(i16 signext %x) {
 ...
}
```

This adds verifier, regbankselect, and instruction selection support for
G_ASSERT_SEXT equivalent to G_ASSERT_ZEXT.

Differential Revision: https://reviews.llvm.org/D96890
2021-02-17 13:10:34 -08:00
David Zarzycki 161e826c58 [lit] Add "early_tests" config option
With enough cores, the slowest tests can significantly change the total testing time if they happen to run late. With this change, a test suite can improve performance (for high-end systems) by listing just a few of the slowest tests up front.

Reviewed By: jdenny, jhenderson

Differential Revision: https://reviews.llvm.org/D96594
2021-02-17 06:32:04 -05:00
Thomas Preud'homme 1e2d50936a Add lit config for dir with standalone tests
Some test systems do not use lit for test discovery but only for its
substitution and test selection because they use another way of managing
test collections, e.g. CTest. This forces those tests to be invoked with
lit --no-indirectly-run-check. When a mix of lit version is in use, it
requires to detect the availability of that option.

This commit provides a new config option standalone_tests to signal a
directory made of tests meant to run as standalone. When this option is
set, lit skips test discovery and the indirectly run check. It also adds
the missing documentation for --no-indirectly-run-check.

Reviewed By: jdenny

Differential Revision: https://reviews.llvm.org/D94766
2021-02-17 10:38:58 +00:00
Alexander Shaposhnikov cdcb60a820 [llvm-libtool] Emit warnings for files without symbols
1. Emit warnings for files without symbols.
2. Add -no_warning_for_no_symbols.

Test plan: make check-all

Differential revision: https://reviews.llvm.org/D95843
2021-02-16 17:52:12 -08:00
Fangrui Song c465429f28 [llvm-objcopy] Delete --build-id-link-{dir,input,output}
The few options are niche. They solved a problem which was traditionally solved
with more shell commands (`llvm-readelf -n` fetches the Build ID. Then
`ln` is used to hard link the file to a directory derived from the Build ID.)

Due to limitation, they are no longer used by Fuchsia and they don't appear to
be used elsewhere (checked with Google Search and Debian Code Search). So delete
them without a transition period.

Announcement: https://lists.llvm.org/pipermail/llvm-dev/2021-February/148446.html

Differential Revision: https://reviews.llvm.org/D96310
2021-02-15 11:17:32 -08:00
Caroline Concatto 99dbc0fa76 [LangRef] Increase size of title underline for experimental.vector.reverse 2021-02-15 15:19:26 +00:00
Caroline Concatto 2d728bbff5 [CodeGen][SelectionDAG]Add new intrinsic experimental.vector.reverse
This patch adds  a new intrinsic experimental.vector.reduce that takes a single
vector and returns a vector of matching type but with the original lane order
 reversed. For example:

```
vector.reverse(<A,B,C,D>) ==> <D,C,B,A>
```

The new intrinsic supports fixed and scalable vectors types.
The fixed-width vector relies on shufflevector to maintain existing behaviour.
Scalable vector uses the new ISD node - VECTOR_REVERSE.

This new intrinsic is one of the named shufflevector intrinsics proposed on the
mailing-list in the RFC at [1].

Patch by Paul Walker (@paulwalker-arm).

[1] https://lists.llvm.org/pipermail/llvm-dev/2020-November/146864.html

Differential Revision: https://reviews.llvm.org/D94883
2021-02-15 13:39:43 +00:00
Juneyoung Lee 1f6ec3d08f [LangRef] Update memory access ops to raise UB if ptrs are not well defined
In the past, it was stated in D87994 that it is allowed to dereference a pointer that is partially undefined
if all of its possible representations fit into a dereferenceable range.
The motivation of the direction was to make a range analysis helpful for assuring dereferenceability.
Even if a range analysis concludes that its offset is within bounds, the offset could still be partially undefined; to utilize the range analysis, this relaxation was necessary.
https://groups.google.com/g/llvm-dev/c/2Qk4fOHUoAE/m/KcvYMEgOAgAJ has more context about this.

However, this is currently blocking another optimization, which is annotating the noundef attribute for library functions' arguments. D95122 is the patch.
Currently, there are quite a few library functions which cannot have noundef attached to its pointer argument because it can be transformed from load/store.
For example, MemCpyOpt can convert stores into memset:

```
store p, i32 0
store (p+1), i32 0 // Since currently it is allowed for store to have partially undefined pointer..
->
memset(p, 0, 8)    // memset cannot guarantee that its ptr argument is noundef.
```

A bigger problem is that this makes unclear which library functions are allowed to have 'noundef' and which functions aren't (e.g., strlen).
This makes annotating noundef almost impossible for this kind of functions.

This patch proposes that all memory operations should have well-defined pointers.
For memset/memcpy, it is semantically equivalent to running a loop until the size is met (and branching on undef is UB), so the size is also updated to be well-defined.

Strictly speaking, this again violates the implication of dereferenceability from range analysis result.
However, I think this is okay for the following reasons:

1. It seems the existing analyses in the LLVM main repo does not have conflicting implementation with the new proposal.
`isDereferenceableAndAlignedPointer` works only when the GEP offset is constant, and `isDereferenceableAndAlignedInLoop` is also fine.

2. A possible miscompilation happens only when the source has a pointer with a *partially* undefined offset (it's okay with poison because there is no 'partially poison' value).
But, at least I'm not aware of a language using LLVM as backend that has a well-defined program while allowing partially undefined pointers.
There might be such a language that I'm not aware of, but improving the performance of the mainstream languages like C and Rust is more important IMHO.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D95238
2021-02-13 14:13:19 +09:00
Vedant Kumar 0c4935bb85 [docs/Coverage] Document -show-region-summary
As a drive-by, fix the section in the clang docs about the number of
statistics visible in a report.
2021-02-12 12:05:45 -08:00
Akira Hatanaka ed4718eccb [ObjC][ARC] Use operand bundle 'clang.arc.attachedcall' instead of
explicitly emitting retainRV or claimRV calls in the IR

Background:

This fixes a longstanding problem where llvm breaks ARC's autorelease
optimization (see the link below) by separating calls from the marker
instructions or retainRV/claimRV calls. The backend changes are in
https://reviews.llvm.org/D92569.

https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue

What this patch does to fix the problem:

- The front-end adds operand bundle "clang.arc.attachedcall" to calls,
  which indicates the call is implicitly followed by a marker
  instruction and an implicit retainRV/claimRV call that consumes the
  call result. In addition, it emits a call to
  @llvm.objc.clang.arc.noop.use, which consumes the call result, to
  prevent the middle-end passes from changing the return type of the
  called function. This is currently done only when the target is arm64
  and the optimization level is higher than -O0.

- ARC optimizer temporarily emits retainRV/claimRV calls after the calls
  with the operand bundle in the IR and removes the inserted calls after
  processing the function.

- ARC contract pass emits retainRV/claimRV calls after the call with the
  operand bundle. It doesn't remove the operand bundle on the call since
  the backend needs it to emit the marker instruction. The retainRV and
  claimRV calls are emitted late in the pipeline to prevent optimization
  passes from transforming the IR in a way that makes it harder for the
  ARC middle-end passes to figure out the def-use relationship between
  the call and the retainRV/claimRV calls (which is the cause of
  PR31925).

- The function inliner removes an autoreleaseRV call in the callee if
  nothing in the callee prevents it from being paired up with the
  retainRV/claimRV call in the caller. It then inserts a release call if
  claimRV is attached to the call since autoreleaseRV+claimRV is
  equivalent to a release. If it cannot find an autoreleaseRV call, it
  tries to transfer the operand bundle to a function call in the callee.
  This is important since the ARC optimizer can remove the autoreleaseRV
  returning the callee result, which makes it impossible to pair it up
  with the retainRV/claimRV call in the caller. If that fails, it simply
  emits a retain call in the IR if retainRV is attached to the call and
  does nothing if claimRV is attached to it.

- SCCP refrains from replacing the return value of a call with a
  constant value if the call has the operand bundle. This ensures the
  call always has at least one user (the call to
  @llvm.objc.clang.arc.noop.use).

- This patch also fixes a bug in replaceUsesOfNonProtoConstant where
  multiple operand bundles of the same kind were being added to a call.

Future work:

- Use the operand bundle on x86-64.

- Fix the auto upgrader to convert call+retainRV/claimRV pairs into
  calls with the operand bundles.

rdar://71443534

Differential Revision: https://reviews.llvm.org/D92808
2021-02-12 09:51:57 -08:00
Sjoerd Meijer cc4dcd48b8 [MIRLangRef] Document MachineOperand comments
Late follow-up of D74306 to document MachineOperand comments in
MIRLangRef.

Differential Revision: https://reviews.llvm.org/D96518
2021-02-12 10:15:47 +00:00
Kristof Beyls f816cf6a47 [DeveloperPolicy] Specify LLVM's license more clearly.
Before, the first mention of LLVM's license on the developer policy page stated
that LLVM's license is Apache 2. This patch makes that more accurate by
mentioning the LLVM exception this first time the LLVM license is discussed on
that page, i.e. Apache-2.0 with LLVM-exception.

Technically, the correct SPDX identifier for LLVM's license is 'Apache-2.0 WITH
LLVM-exception', but I thought that writing the 'WITH' in lower case made the
paragraph easier to read without reducing clarity.

Differential Revision: https://reviews.llvm.org/D96482
2021-02-12 09:16:43 +00:00
Guillaume Chatelet 8f3518e69b Fix incorrect indentation in LangRef.rst 2021-02-11 20:47:43 +00:00
Guillaume Chatelet ca052adf07 Fix incorrect indentation in LangRef.rst 2021-02-11 20:34:19 +00:00