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Commit Graph

321 Commits

Author SHA1 Message Date
Francis Visoiu Mistrih
a0d8c69089 [Remarks][ThinLTO] Use the correct file extension based on the format
Since we now have multiple formats, the ThinLTO remark files should also
respect that.
2019-12-02 13:04:43 -08:00
evgeny
fa92ba961c [ThinLTO] Make ValueInfo::operator bool() explicit
Differential revision: https://reviews.llvm.org/D70383
2019-11-19 12:46:09 +03:00
Teresa Johnson
0d09270c42 ThinLTO: Fix assembler to emit alwaysInline in the summary
Summary: The earlier commit (https://reviews.llvm.org/D70014) missed this one : If Always_Inline happens to be the only entry in FuncFlags, then the assembler will not print it in the summary.

Patch by Bharathi Seshadri <bseshadr@cisco.com>

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70323
2019-11-18 15:02:13 -08:00
Teresa Johnson
1ab13376f4 ThinLTO : Import always_inline functions irrespective of the threshold
Summary: A user can force a function to be inlined by specifying the always_inline attribute. Currently, thinlto implementation is not aware of always_inline functions and does not guarantee import of such functions, which in turn can prevent inlining of such functions.

Patch by Bharathi Seshadri <bseshadr@cisco.com>

Reviewers: tejohnson

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70014
2019-11-08 17:02:01 -08:00
evgeny
2729417b4d [ThinLTO] Fix bug when importing writeonly variables
Patch enables import of write-only variables with non-trivial initializers
to fix linker errors. Initializers of imported variables are converted to
'zeroinitializer' to avoid promotion of referenced objects.

Differential revision: https://reviews.llvm.org/D70006
2019-11-08 20:50:34 +03:00
evgeny
7372ca12be [ThinLTO] Import readonly vars with refs
Patch allows importing declarations of functions and variables, referenced
by the initializer of some other readonly variable.
Differential revision: https://reviews.llvm.org/D69561
2019-11-07 15:13:35 +03:00
Teresa Johnson
e9043f8a26 Recommit "[ThinLTO] Handle GUID collision in import global processing""
This recommits cc0b9647b76178bc3869bbfff80535ad86366472 which was
reverted in d39d1a2f87aca3cfabe58ecfa5146879baa70096.

I added a fix for an issue found when testing via distributed ThinLTO,
and added a test case for that failure.
2019-11-01 13:57:01 -07:00
Teresa Johnson
7143e76354 Revert "[LLD][ThinLTO] Handle GUID collision in import global processing"
This reverts commit cc0b9647b76178bc3869bbfff80535ad86366472.

The commit is causing a failure in internal testing. Will recommit with
a fix later.
2019-11-01 10:02:58 -07:00
Teresa Johnson
0230a0a970 [ThinLTO/WPD] Fix index-based WPD for available_externally vtables
Summary:
Clang does not add type metadata to available_externally vtables. When
choosing a summary to look at for virtual function definitions, make
sure we skip summaries for any available externally vtables as they will
not describe any virtual function functions, which are only summarized
in the presence of type metadata on the vtable def. Simply look for the
corresponding strong def's summary.

Also add handling for same-named local vtables with the same GUID
because of same-named files without enough distinguishing path.
In that case we return a conservative result with no devirtualization.

Reviewers: pcc, davidxl, evgeny777

Subscribers: mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69452
2019-10-30 17:59:08 -07:00
Teresa Johnson
a378559c07 [LLD][ThinLTO] Handle GUID collision in import global processing
Summary:
If there are a GUID collision between two globals checking the
summarylist from the import index to make assumption can be dangerous.

Do not assume that a GlobalValue that has a GlobalVarSummary
actually is a GlobalVariable as it can be another GlobalValue with
the same GUID that the summary is connected to.

Patch by Joel Klinghed (the_jk@opera.com)

Reviewers: evgeny777, tejohnson

Reviewed By: tejohnson

Subscribers: tejohnson, dblaikie, MaskRay, mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67322
2019-10-25 12:36:01 -07:00
Eugene Leviant
b54476ab94 [ThinLTO] Don't internalize during promotion
Differential revision: https://reviews.llvm.org/D69107

llvm-svn: 375493
2019-10-22 09:24:12 +00:00
Eugene Leviant
1a39c6003e One more attempt to fix PS4 buildbot after r375219
PS4 buildbot seems to be dropping variable names for some reason

llvm-svn: 375237
2019-10-18 14:11:19 +00:00
Eugene Leviant
9c01211772 Attempt to fix PS4 buildbot after r375219
llvm-svn: 375235
2019-10-18 13:52:51 +00:00
Eugene Leviant
7787d23a97 [ThinLTOCodeGenerator] Add support for index-based WPD
Differential revision: https://reviews.llvm.org/D68950

llvm-svn: 375219
2019-10-18 10:54:14 +00:00
Oliver Stannard
6aaf81e821 Reland: Dead Virtual Function Elimination
Remove dead virtual functions from vtables with
replaceNonMetadataUsesWith, so that CGProfile metadata gets cleaned up
correctly.

Original commit message:

Currently, it is hard for the compiler to remove unused C++ virtual
functions, because they are all referenced from vtables, which are referenced
by constructors. This means that if the constructor is called from any live
code, then we keep every virtual function in the final link, even if there
are no call sites which can use it.

This patch allows unused virtual functions to be removed during LTO (and
regular compilation in limited circumstances) by using type metadata to match
virtual function call sites to the vtable slots they might load from. This
information can then be used in the global dead code elimination pass instead
of the references from vtables to virtual functions, to more accurately
determine which functions are reachable.

To make this transformation safe, I have changed clang's code-generation to
always load virtual function pointers using the llvm.type.checked.load
intrinsic, instead of regular load instructions. I originally tried writing
this using clang's existing code-generation, which uses the llvm.type.test
and llvm.assume intrinsics after doing a normal load. However, it is possible
for optimisations to obscure the relationship between the GEP, load and
llvm.type.test, causing GlobalDCE to fail to find virtual function call
sites.

The existing linkage and visibility types don't accurately describe the scope
in which a virtual call could be made which uses a given vtable. This is
wider than the visibility of the type itself, because a virtual function call
could be made using a more-visible base class. I've added a new
!vcall_visibility metadata type to represent this, described in
TypeMetadata.rst. The internalization pass and libLTO have been updated to
change this metadata when linking is performed.

This doesn't currently work with ThinLTO, because it needs to see every call
to llvm.type.checked.load in the linkage unit. It might be possible to
extend this optimisation to be able to use the ThinLTO summary, as was done
for devirtualization, but until then that combination is rejected in the
clang driver.

To test this, I've written a fuzzer which generates random C++ programs with
complex class inheritance graphs, and virtual functions called through object
and function pointers of different types. The programs are spread across
multiple translation units and DSOs to test the different visibility
restrictions.

I've also tried doing bootstrap builds of LLVM to test this. This isn't
ideal, because only classes in anonymous namespaces can be optimised with
-fvisibility=default, and some parts of LLVM (plugins and bugpoint) do not
work correctly with -fvisibility=hidden. However, there are only 12 test
failures when building with -fvisibility=hidden (and an unmodified compiler),
and this change does not cause any new failures for either value of
-fvisibility.

On the 7 C++ sub-benchmarks of SPEC2006, this gives a geomean code-size
reduction of ~6%, over a baseline compiled with "-O2 -flto
-fvisibility=hidden -fwhole-program-vtables". The best cases are reductions
of ~14% in 450.soplex and 483.xalancbmk, and there are no code size
increases.

I've also run this on a set of 8 mbed-os examples compiled for Armv7M, which
show a geomean size reduction of ~3%, again with no size increases.

I had hoped that this would have no effect on performance, which would allow
it to awlays be enabled (when using -fwhole-program-vtables). However, the
changes in clang to use the llvm.type.checked.load intrinsic are causing ~1%
performance regression in the C++ parts of SPEC2006. It should be possible to
recover some of this perf loss by teaching optimisations about the
llvm.type.checked.load intrinsic, which would make it worth turning this on
by default (though it's still dependent on -fwhole-program-vtables).

Differential revision: https://reviews.llvm.org/D63932

llvm-svn: 375094
2019-10-17 09:58:57 +00:00
Eugene Leviant
37fc87859f [ThinLTO] Import virtual method with single implementation in hybrid mode
Differential revision: https://reviews.llvm.org/D68782

llvm-svn: 375083
2019-10-17 07:46:18 +00:00
Jorge Gorbe Moya
6a19d78c0a Revert "Dead Virtual Function Elimination"
This reverts commit 9f6a873268e1ad9855873d9d8007086c0d01cf4f.

llvm-svn: 374844
2019-10-14 23:25:25 +00:00
Oliver Stannard
901c588c1f Dead Virtual Function Elimination
Currently, it is hard for the compiler to remove unused C++ virtual
functions, because they are all referenced from vtables, which are referenced
by constructors. This means that if the constructor is called from any live
code, then we keep every virtual function in the final link, even if there
are no call sites which can use it.

This patch allows unused virtual functions to be removed during LTO (and
regular compilation in limited circumstances) by using type metadata to match
virtual function call sites to the vtable slots they might load from. This
information can then be used in the global dead code elimination pass instead
of the references from vtables to virtual functions, to more accurately
determine which functions are reachable.

To make this transformation safe, I have changed clang's code-generation to
always load virtual function pointers using the llvm.type.checked.load
intrinsic, instead of regular load instructions. I originally tried writing
this using clang's existing code-generation, which uses the llvm.type.test
and llvm.assume intrinsics after doing a normal load. However, it is possible
for optimisations to obscure the relationship between the GEP, load and
llvm.type.test, causing GlobalDCE to fail to find virtual function call
sites.

The existing linkage and visibility types don't accurately describe the scope
in which a virtual call could be made which uses a given vtable. This is
wider than the visibility of the type itself, because a virtual function call
could be made using a more-visible base class. I've added a new
!vcall_visibility metadata type to represent this, described in
TypeMetadata.rst. The internalization pass and libLTO have been updated to
change this metadata when linking is performed.

This doesn't currently work with ThinLTO, because it needs to see every call
to llvm.type.checked.load in the linkage unit. It might be possible to
extend this optimisation to be able to use the ThinLTO summary, as was done
for devirtualization, but until then that combination is rejected in the
clang driver.

To test this, I've written a fuzzer which generates random C++ programs with
complex class inheritance graphs, and virtual functions called through object
and function pointers of different types. The programs are spread across
multiple translation units and DSOs to test the different visibility
restrictions.

I've also tried doing bootstrap builds of LLVM to test this. This isn't
ideal, because only classes in anonymous namespaces can be optimised with
-fvisibility=default, and some parts of LLVM (plugins and bugpoint) do not
work correctly with -fvisibility=hidden. However, there are only 12 test
failures when building with -fvisibility=hidden (and an unmodified compiler),
and this change does not cause any new failures for either value of
-fvisibility.

On the 7 C++ sub-benchmarks of SPEC2006, this gives a geomean code-size
reduction of ~6%, over a baseline compiled with "-O2 -flto
-fvisibility=hidden -fwhole-program-vtables". The best cases are reductions
of ~14% in 450.soplex and 483.xalancbmk, and there are no code size
increases.

I've also run this on a set of 8 mbed-os examples compiled for Armv7M, which
show a geomean size reduction of ~3%, again with no size increases.

I had hoped that this would have no effect on performance, which would allow
it to awlays be enabled (when using -fwhole-program-vtables). However, the
changes in clang to use the llvm.type.checked.load intrinsic are causing ~1%
performance regression in the C++ parts of SPEC2006. It should be possible to
recover some of this perf loss by teaching optimisations about the
llvm.type.checked.load intrinsic, which would make it worth turning this on
by default (though it's still dependent on -fwhole-program-vtables).

Differential revision: https://reviews.llvm.org/D63932

llvm-svn: 374539
2019-10-11 11:59:55 +00:00
Teresa Johnson
d2f6522f79 [ThinLTO/WPD] Ensure devirtualized targets use promoted symbol when necessary
Summary:
This fixes a hole in the handling of devirtualized targets that were
local but need promoting due to devirtualization in another module. We
were not correctly referencing the promoted symbol in some cases. Make
sure the code that updates the name also looks at the ExportedGUIDs set
by utilizing a callback that checks all conditions (the callback
utilized by the internalization/promotion code).

Reviewers: pcc, davidxl, hiraditya

Subscribers: mehdi_amini, Prazek, inglorion, steven_wu, dexonsmith, dang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68159

llvm-svn: 373485
2019-10-02 16:36:59 +00:00
Petr Hosek
24e3a769e6 Reland "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM"
This patch contains the basic functionality for reporting potentially
incorrect usage of __builtin_expect() by comparing the developer's
annotation against a collected PGO profile. A more detailed proposal and
discussion appears on the CFE-dev mailing list
(http://lists.llvm.org/pipermail/cfe-dev/2019-July/062971.html) and a
prototype of the initial frontend changes appear here in D65300

We revised the work in D65300 by moving the misexpect check into the
LLVM backend, and adding support for IR and sampling based profiles, in
addition to frontend instrumentation.

We add new misexpect metadata tags to those instructions directly
influenced by the llvm.expect intrinsic (branch, switch, and select)
when lowering the intrinsics. The misexpect metadata contains
information about the expected target of the intrinsic so that we can
check against the correct PGO counter when emitting diagnostics, and the
compiler's values for the LikelyBranchWeight and UnlikelyBranchWeight.
We use these branch weight values to determine when to emit the
diagnostic to the user.

A future patch should address the comment at the top of
LowerExpectIntrisic.cpp to hoist the LikelyBranchWeight and
UnlikelyBranchWeight values into a shared space that can be accessed
outside of the LowerExpectIntrinsic pass. Once that is done, the
misexpect metadata can be updated to be smaller.

In the long term, it is possible to reconstruct portions of the
misexpect metadata from the existing profile data. However, we have
avoided this to keep the code simple, and because some kind of metadata
tag will be required to identify which branch/switch/select instructions
are influenced by the use of llvm.expect

Patch By: paulkirth
Differential Revision: https://reviews.llvm.org/D66324

llvm-svn: 371635
2019-09-11 16:19:50 +00:00
Dmitri Gribenko
145a0310ec Revert "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM"
This reverts commit r371584. It introduced a dependency from compiler-rt
to llvm/include/ADT, which is problematic for multiple reasons.

One is that it is a novel dependency edge, which needs cross-compliation
machinery for llvm/include/ADT (yes, it is true that right now
compiler-rt included only header-only libraries, however, if we allow
compiler-rt to depend on anything from ADT, other libraries will
eventually get used).

Secondly, depending on ADT from compiler-rt exposes ADT symbols from
compiler-rt, which would cause ODR violations when Clang is built with
the profile library.

llvm-svn: 371598
2019-09-11 09:16:17 +00:00
Petr Hosek
1b31f282e7 clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM
This patch contains the basic functionality for reporting potentially
incorrect usage of __builtin_expect() by comparing the developer's
annotation against a collected PGO profile. A more detailed proposal and
discussion appears on the CFE-dev mailing list
(http://lists.llvm.org/pipermail/cfe-dev/2019-July/062971.html) and a
prototype of the initial frontend changes appear here in D65300

We revised the work in D65300 by moving the misexpect check into the
LLVM backend, and adding support for IR and sampling based profiles, in
addition to frontend instrumentation.

We add new misexpect metadata tags to those instructions directly
influenced by the llvm.expect intrinsic (branch, switch, and select)
when lowering the intrinsics. The misexpect metadata contains
information about the expected target of the intrinsic so that we can
check against the correct PGO counter when emitting diagnostics, and the
compiler's values for the LikelyBranchWeight and UnlikelyBranchWeight.
We use these branch weight values to determine when to emit the
diagnostic to the user.

A future patch should address the comment at the top of
LowerExpectIntrisic.cpp to hoist the LikelyBranchWeight and
UnlikelyBranchWeight values into a shared space that can be accessed
outside of the LowerExpectIntrinsic pass. Once that is done, the
misexpect metadata can be updated to be smaller.

In the long term, it is possible to reconstruct portions of the
misexpect metadata from the existing profile data. However, we have
avoided this to keep the code simple, and because some kind of metadata
tag will be required to identify which branch/switch/select instructions
are influenced by the use of llvm.expect

Patch By: paulkirth
Differential Revision: https://reviews.llvm.org/D66324

llvm-svn: 371584
2019-09-11 01:09:16 +00:00
Amy Huang
062b5d40cb Reland "Change the X86 datalayout to add three address spaces
for 32 bit signed, 32 bit unsigned, and 64 bit pointers."
This reverts 57076d3199fc2b0af4a3736b7749dd5462cacda5.

Original review at https://reviews.llvm.org/D64931.
Review for added fix at https://reviews.llvm.org/D66843.

llvm-svn: 371568
2019-09-10 23:15:38 +00:00
Petr Hosek
aa3ac06edb Revert "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM"
This reverts commit r371484: this broke sanitizer-x86_64-linux-fast bot.

llvm-svn: 371488
2019-09-10 06:25:13 +00:00
Petr Hosek
392b87e7b6 clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM
This patch contains the basic functionality for reporting potentially
incorrect usage of __builtin_expect() by comparing the developer's
annotation against a collected PGO profile. A more detailed proposal and
discussion appears on the CFE-dev mailing list
(http://lists.llvm.org/pipermail/cfe-dev/2019-July/062971.html) and a
prototype of the initial frontend changes appear here in D65300

We revised the work in D65300 by moving the misexpect check into the
LLVM backend, and adding support for IR and sampling based profiles, in
addition to frontend instrumentation.

We add new misexpect metadata tags to those instructions directly
influenced by the llvm.expect intrinsic (branch, switch, and select)
when lowering the intrinsics. The misexpect metadata contains
information about the expected target of the intrinsic so that we can
check against the correct PGO counter when emitting diagnostics, and the
compiler's values for the LikelyBranchWeight and UnlikelyBranchWeight.
We use these branch weight values to determine when to emit the
diagnostic to the user.

A future patch should address the comment at the top of
LowerExpectIntrisic.cpp to hoist the LikelyBranchWeight and
UnlikelyBranchWeight values into a shared space that can be accessed
outside of the LowerExpectIntrinsic pass. Once that is done, the
misexpect metadata can be updated to be smaller.

In the long term, it is possible to reconstruct portions of the
misexpect metadata from the existing profile data. However, we have
avoided this to keep the code simple, and because some kind of metadata
tag will be required to identify which branch/switch/select instructions
are influenced by the use of llvm.expect

Patch By: paulkirth
Differential Revision: https://reviews.llvm.org/D66324

llvm-svn: 371484
2019-09-10 03:11:39 +00:00
Richard Trieu
153062896c Revert r370105 - Update two x86 datalayouts for r370083, looks like racing commits
r370083 has been reverted, which this change depends on.

llvm-svn: 370147
2019-08-28 01:55:06 +00:00
Vlad Tsyrklevich
b6303e0ac6 Revert "Change the X86 datalayout to add three address spaces for 32 bit signed,"
This reverts commit r370083 because it caused check-lld failures on
sanitizer-x86_64-linux-fast.

llvm-svn: 370142
2019-08-28 01:08:54 +00:00
Reid Kleckner
8c87cc042d Update two x86 datalayouts for r370083, looks like racing commits
llvm-svn: 370105
2019-08-27 19:55:10 +00:00
Amy Huang
1082859b72 Change the X86 datalayout to add three address spaces for 32 bit signed,
32 bit unsigned, and 64 bit pointers.

llvm-svn: 370083
2019-08-27 17:46:53 +00:00
Teresa Johnson
c649b1f9bb [ThinLTO] Fix handling of weak interposable symbols
Summary:
Keep aliasees alive if their alias is live, otherwise we end up with an
alias to a declaration, which is invalid. This can happen when the
aliasee is weak and non-prevailing.

This fix exposed the fact that we were then attempting to internalize
the weak symbol, which was not exported as it was not prevailing. We
should not internalize interposable symbols in general, unless this is
the prevailing copy, since it can lead to incorrect inlining and other
optimizations. Most of the changes in this patch are due to the
restructuring required to pass down the prevailing callback.

Finally, while implementing the test cases, I found that in the case of
a weak aliasee that is still marked not live because its alias isn't
live, after dropping the definition we incorrectly marked the
declaration with weak linkage when resolving prevailing symbols in the
module. This was due to some special case handling for symbols marked
WeakLinkage in the summary located before instead of after a subsequent
check for the symbol being a declaration. It turns out that we don't
actually need this special case handling any more (looking back at the
history, when that was added the code was structured quite differently)
- we will correctly mark with weak linkage further below when the
definition hasn't been dropped.

Fixes PR42542.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, steven_wu, dexonsmith, dang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66264

llvm-svn: 369766
2019-08-23 15:18:58 +00:00
David L. Jones
96783c0442 [NewPM][PassInstrumentation] Fix test added in r369024.
llvm-lto2 doesn't treat "-" as stdout, so the test added in r369024 creates a
file named "-.0". This patch makes the test look more like other tests that use
llvm-lto2.

llvm-svn: 369066
2019-08-15 23:24:14 +00:00
Taewook Oh
67a07e74bc [NewPM][PassInstrumentation] IR printing support for (Thin)LTO
Summary: IR printing has not been correctly supported with (Thin)LTO if the new pass manager is enabled. Previously we only get outputs from backend(codegen) passes, as they are still under legacy pass manager even when the new pass manager is enabled. This patch addresses the issue and enables IR printing for optimization passes with new pass manager + (Thin)LTO setting.

Reviewers: fedor.sergeev, philip.pfaffe

Subscribers: mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, dang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66253

llvm-svn: 369024
2019-08-15 17:47:44 +00:00
Tim Northover
e5745c32fd IR: print value numbers for unnamed function arguments
For consistency with normal instructions and clarity when reading IR,
it's best to print the %0, %1, ... names of function arguments in
definitions.

Also modifies the parser to accept IR in that form for obvious reasons.

llvm-svn: 367755
2019-08-03 14:28:34 +00:00
Teresa Johnson
07f2331c21 Use llvm-nm instead of nm in new test to unbreak Windows bot
New test added in r367679 used nm and should use llvm-nm.

llvm-svn: 367688
2019-08-02 15:49:39 +00:00
Teresa Johnson
d13618986a Fix new test try 2
Fix second (and last) instance of wrong Input file name in new test
added in r367679.

llvm-svn: 367682
2019-08-02 13:49:48 +00:00
Teresa Johnson
ba00c92a1a Fix new test
Thew new test added in r367679 was using the wrong copy of the Input
file.

llvm-svn: 367680
2019-08-02 13:26:18 +00:00
Teresa Johnson
0273961b82 [ThinLTO] Implement index-based WPD
This patch adds support to the WholeProgramDevirt pass to perform
index-based WPD, which is invoked from ThinLTO during the thin link.

The ThinLTO backend (WPD import phase) behaves the same regardless of
whether the WPD decisions were made with the index-based or (the
existing) IR-based analysis.

Depends on D54815.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, arphaman, dang, llvm-commits

Differential Revision: https://reviews.llvm.org/D55153

llvm-svn: 367679
2019-08-02 13:10:52 +00:00
Bob Haarman
f4fcc00e4d [ThinLTO] only emit used or referenced CFI records to index
Summary: We emit CFI_FUNCTION_DEFS and CFI_FUNCTION_DECLS to
distributed ThinLTO indices to implement indirect function call
checking.  This change causes us to only emit entries for functions
that are either defined or used by the module we're writing the index
for (instead of all functions in the combined index), which can make
the indices substantially smaller.

Fixes PR42378.

Reviewers: pcc, vitalybuka, eugenis

Subscribers: mehdi_amini, hiraditya, dexonsmith, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63887

llvm-svn: 365537
2019-07-09 18:50:55 +00:00
Yonghong Song
61809186ed [BPF] add new intrinsics preserve_{array,union,struct}_access_index
For background of BPF CO-RE project, please refer to
  http://vger.kernel.org/bpfconf2019.html
In summary, BPF CO-RE intends to compile bpf programs
adjustable on struct/union layout change so the same
program can run on multiple kernels with adjustment
before loading based on native kernel structures.

In order to do this, we need keep track of GEP(getelementptr)
instruction base and result debuginfo types, so we
can adjust on the host based on kernel BTF info.
Capturing such information as an IR optimization is hard
as various optimization may have tweaked GEP and also
union is replaced by structure it is impossible to track
fieldindex for union member accesses.

Three intrinsic functions, preserve_{array,union,struct}_access_index,
are introducted.
  addr = preserve_array_access_index(base, index, dimension)
  addr = preserve_union_access_index(base, di_index)
  addr = preserve_struct_access_index(base, gep_index, di_index)
here,
  base: the base pointer for the array/union/struct access.
  index: the last access index for array, the same for IR/DebugInfo layout.
  dimension: the array dimension.
  gep_index: the access index based on IR layout.
  di_index: the access index based on user/debuginfo types.

For example, for the following example,
  $ cat test.c
  struct sk_buff {
     int i;
     int b1:1;
     int b2:2;
     union {
       struct {
         int o1;
         int o2;
       } o;
       struct {
         char flags;
         char dev_id;
       } dev;
       int netid;
     } u[10];
  };

  static int (*bpf_probe_read)(void *dst, int size, const void *unsafe_ptr)
      = (void *) 4;

  #define _(x) (__builtin_preserve_access_index(x))

  int bpf_prog(struct sk_buff *ctx) {
    char dev_id;
    bpf_probe_read(&dev_id, sizeof(char), _(&ctx->u[5].dev.dev_id));
    return dev_id;
  }
  $ clang -target bpf -O2 -g -emit-llvm -S -mllvm -print-before-all \
    test.c >& log

The generated IR looks like below:

  ...
  define dso_local i32 @bpf_prog(%struct.sk_buff*) #0 !dbg !15 {
    %2 = alloca %struct.sk_buff*, align 8
    %3 = alloca i8, align 1
    store %struct.sk_buff* %0, %struct.sk_buff** %2, align 8, !tbaa !45
    call void @llvm.dbg.declare(metadata %struct.sk_buff** %2, metadata !43, metadata !DIExpression()), !dbg !49
    call void @llvm.lifetime.start.p0i8(i64 1, i8* %3) #4, !dbg !50
    call void @llvm.dbg.declare(metadata i8* %3, metadata !44, metadata !DIExpression()), !dbg !51
    %4 = load i32 (i8*, i32, i8*)*, i32 (i8*, i32, i8*)** @bpf_probe_read, align 8, !dbg !52, !tbaa !45
    %5 = load %struct.sk_buff*, %struct.sk_buff** %2, align 8, !dbg !53, !tbaa !45
    %6 = call [10 x %union.anon]* @llvm.preserve.struct.access.index.p0a10s_union.anons.p0s_struct.sk_buffs(
         %struct.sk_buff* %5, i32 2, i32 3), !dbg !53, !llvm.preserve.access.index !19
    %7 = call %union.anon* @llvm.preserve.array.access.index.p0s_union.anons.p0a10s_union.anons(
         [10 x %union.anon]* %6, i32 1, i32 5), !dbg !53
    %8 = call %union.anon* @llvm.preserve.union.access.index.p0s_union.anons.p0s_union.anons(
         %union.anon* %7, i32 1), !dbg !53, !llvm.preserve.access.index !26
    %9 = bitcast %union.anon* %8 to %struct.anon.0*, !dbg !53
    %10 = call i8* @llvm.preserve.struct.access.index.p0i8.p0s_struct.anon.0s(
         %struct.anon.0* %9, i32 1, i32 1), !dbg !53, !llvm.preserve.access.index !34
    %11 = call i32 %4(i8* %3, i32 1, i8* %10), !dbg !52
    %12 = load i8, i8* %3, align 1, !dbg !54, !tbaa !55
    %13 = sext i8 %12 to i32, !dbg !54
    call void @llvm.lifetime.end.p0i8(i64 1, i8* %3) #4, !dbg !56
    ret i32 %13, !dbg !57
  }

  !19 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "sk_buff", file: !3, line: 1, size: 704, elements: !20)
  !26 = distinct !DICompositeType(tag: DW_TAG_union_type, scope: !19, file: !3, line: 5, size: 64, elements: !27)
  !34 = distinct !DICompositeType(tag: DW_TAG_structure_type, scope: !26, file: !3, line: 10, size: 16, elements: !35)

Note that @llvm.preserve.{struct,union}.access.index calls have metadata llvm.preserve.access.index
attached to instructions to provide struct/union debuginfo type information.

For &ctx->u[5].dev.dev_id,
  . The "%6 = ..." represents struct member "u" with index 2 for IR layout and index 3 for DI layout.
  . The "%7 = ..." represents array subscript "5".
  . The "%8 = ..." represents union member "dev" with index 1 for DI layout.
  . The "%10 = ..." represents struct member "dev_id" with index 1 for both IR and DI layout.

Basically, traversing the use-def chain recursively for the 3rd argument of bpf_probe_read() and
examining all preserve_*_access_index calls, the debuginfo struct/union/array access index
can be achieved.

The intrinsics also contain enough information to regenerate codes for IR layout.
For array and structure intrinsics, the proper GEP can be constructed.
For union intrinsics, replacing all uses of "addr" with "base" should be enough.

The test case ThinLTO/X86/lazyload_metadata.ll is adjusted to reflect the
new addition of the metadata.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D61810

llvm-svn: 365423
2019-07-09 01:51:36 +00:00
Eugene Leviant
1cec5950f5 [ThinLTO] Attempt to recommit r365188 after alignment fix
llvm-svn: 365215
2019-07-05 15:25:05 +00:00
Eugene Leviant
1492333665 Reverted r365188 due to alignment problems on i686-android
llvm-svn: 365206
2019-07-05 13:26:05 +00:00
Eugene Leviant
f98174731f [ThinLTO] Attempt to recommit r365040 after caching fix
It's possible that some function can load and store the same
variable using the same constant expression:

store %Derived* @foo, %Derived** bitcast (%Base** @bar to %Derived**)
%42 = load %Derived*, %Derived** bitcast (%Base** @bar to %Derived**)

The bitcast expression was mistakenly cached while processing loads,
and never examined later when processing store. This caused @bar to
be mistakenly treated as read-only variable. See load-store-caching.ll.

llvm-svn: 365188
2019-07-05 12:00:10 +00:00
Reid Kleckner
f7383bbaa1 Revert [ThinLTO] Optimize writeonly globals out
This reverts r365040 (git commit 5cacb914758c7f436b47c8362100f10cef14bbc4)

Speculatively reverting, since this appears to have broken check-lld on
Linux. Partial analysis in https://crbug.com/981168.

llvm-svn: 365097
2019-07-04 00:03:30 +00:00
Francis Visoiu Mistrih
f0c4b59ebb [CodeGen] Make branch funnels pass the machine verifier
We previously marked all the tests with branch funnels as
`-verify-machineinstrs=0`.

This is an attempt to fix it.

1) `ICALL_BRANCH_FUNNEL` has no defs. Mark it as `let OutOperandList =
(outs)`

2) After that we hit an assert: ``` Assertion failed: (Op.getValueType()
!= MVT::Other && Op.getValueType() != MVT::Glue && "Chain and glue
operands should occur at end of operand list!"), function AddOperand,
file
/Users/francisvm/llvm/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp,
line 461.  ```

The chain operand was added at the beginning of the operand list. Move
that to the end.

3) After that we hit another verifier issue in the pseudo expansion
where the registers used in the cmps and jmps are not added to the
livein lists. Add the `EFLAGS` to all the new MBBs that we create.

PR39436

Differential Review: https://reviews.llvm.org/D54155

llvm-svn: 365058
2019-07-03 17:16:45 +00:00
Eugene Leviant
a4bd29ba06 [ThinLTO] Optimize writeonly globals out
Differential revision: https://reviews.llvm.org/D63444

llvm-svn: 365040
2019-07-03 14:14:52 +00:00
Teresa Johnson
e843f33c23 [ThinLTO] Reenable test with workaround for known failure
Reenable the testing disabled in r364978 with the same workaround used
for this failure in the cfi-devirt.ll test. The known issue is PR39436,
and the workaround is to add -verify-machineinstrs=0.

llvm-svn: 364997
2019-07-03 02:14:47 +00:00
Teresa Johnson
8b927e15fd [ThinLTO] Work around existing failure exposed by new test
When adding summary entries for index-based WPD (r364960), an added
test also included some additional testing of the existing hybrid
Thin/Regular LTO WPD (test/ThinLTO/X86/devirt.ll). That part of the
test is producing a failure on the llvm-clang-x86_64-expensive-checks-win
bot:

*** Bad machine code: Explicit definition marked as use ***
- function:    __typeid__ZTS1A_0_branch_funnel
- basic block: %bb.0  (0x81d4c58)
- instruction: ICALL_BRANCH_FUNNEL %0:gr64, @0, 16, @_ZN1B1fEi, 48, @_ZN1C1fEi
- operand 0:   %0:gr64
LLVM ERROR: Found 1 machine code errors.

This is functionality unrelated to the summary entries added with my
patch, so I am disabling this part of the new test until it is
addressed. I'll continue to investigate the failure.

llvm-svn: 364978
2019-07-02 23:28:28 +00:00
Teresa Johnson
b7970f9e15 [ThinLTO] Dump input on failure in devirt test
To help track down bug exposed by llvm-clang-x86_64-expensive-checks-win
bot.

llvm-svn: 364973
2019-07-02 22:06:02 +00:00
Teresa Johnson
e45131dbf7 [ThinLTO] Add summary entries for index-based WPD
Summary:
If LTOUnit splitting is disabled, the module summary analysis computes
the summary information necessary to perform single implementation
devirtualization during the thin link with the index and no IR. The
information collected from the regular LTO IR in the current hybrid WPD
algorithm is summarized, including:
1) For vtable definitions, record the function pointers and their offset
within the vtable initializer (subsumes the information collected from
IR by tryFindVirtualCallTargets).
2) A record for each type metadata summarizing the vtable definitions
decorated with that metadata (subsumes the TypeIdentiferMap collected
from IR).

Also added are the necessary bitcode records, and the corresponding
assembly support.

The follow-on index-based WPD patch is D55153.

Depends on D53890.

Reviewers: pcc

Subscribers: mehdi_amini, Prazek, inglorion, eraman, steven_wu, dexonsmith, arphaman, llvm-commits

Differential Revision: https://reviews.llvm.org/D54815

llvm-svn: 364960
2019-07-02 19:38:02 +00:00
Francis Visoiu Mistrih
1e67de55c2 [Remarks] Extend -fsave-optimization-record to specify the format
Use -fsave-optimization-record=<format> to specify a different format
than the default, which is YAML.

For now, only YAML is supported.

llvm-svn: 363573
2019-06-17 16:06:00 +00:00