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Commit Graph

261 Commits

Author SHA1 Message Date
Fangrui Song
e44e8f46a9 ThinLTOBitcodeWriter: drop dso_local when a GlobalVariable is converted to a declaration
If we infer the dso_local flag for -fpic, dso_local should be dropped
when we convert a GlobalVariable a declaration. dso_local causes the
generation of direct access (e.g. R_X86_64_PC32). Such relocations referencing
STB_GLOBAL STV_DEFAULT objects are not allowed in a -shared link.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D74749
2020-03-05 18:09:33 -08:00
Fangrui Song
25a0241f66 [llvm-objdump] -d: print 00000000 <foo>: instead of 00000000 foo:
The new behavior matches GNU objdump. A pair of angle brackets makes tests slightly easier.

`.foo:` is not unique and thus cannot be used in a `CHECK-LABEL:` directive.
Without `-LABEL`, the CHECK line can match the `Disassembly of section`
line and causes the next `CHECK-NEXT:` to fail.

```
Disassembly of section .foo:

0000000000001634 .foo:
```

Bdragon: <> has metalinguistic connotation. it just "feels right"

Reviewed By: rupprecht

Differential Revision: https://reviews.llvm.org/D75713
2020-03-05 18:05:28 -08:00
Francis Visoiu Mistrih
b4279d9528 [LTO][Legacy] Add new API to query Mach-O CPU (sub)type
Tools working with object files on Darwin (e.g. lipo) may need to know
properties like the CPU type and subtype of a bitcode file. The logic of
converting a triple to a Mach-O CPU_(SUB_)TYPE should be provided by
LLVM instead of relying on tools to re-implement it.

Differential Revision: https://reviews.llvm.org/D75067
2020-02-28 12:56:05 -08:00
Yuanfang Chen
dd53274771 Revert "Revert "Reland "[Support] make report_fatal_error abort instead of exit"""
This reverts commit 80a34ae31125aa46dcad47162ba45b152aed968d 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
2dbac841f9 Revert "Revert "Revert "Reland "[Support] make report_fatal_error abort instead of exit""""
This reverts commit bb51d243308dbcc9a8c73180ae7b9e47b98e68fb.
2020-02-13 10:08:05 -08:00
Yuanfang Chen
93e82c22ef Revert "Revert "Reland "[Support] make report_fatal_error abort instead of exit"""
This reverts commit 80a34ae31125aa46dcad47162ba45b152aed968d 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
Yuanfang Chen
c7fb4c55c4 Revert "Reland "[Support] make report_fatal_error abort instead of exit""
This reverts commit rGcd5b308b828e, rGcd5b308b828e, rG8cedf0e2994c.

There are issues to be investigated for polly bots and bots turning on
EXPENSIVE_CHECKS.
2020-02-11 20:41:53 -08:00
Yuanfang Chen
83a2f3c1ba Reland "[Support] make report_fatal_error abort instead of exit"
Summary:
Reland D67847 after D73742 is committed. Replace `sys::Process::Exit(1)`
with `abort` in `report_fatal_error`.

After this patch, for tools turning on `CrashRecoveryContext`,
crash handler installed by `CrashRecoveryContext` is called unless
they installed a non-returning handler using `llvm::install_fatal_error_handler`
like `cc1_main` currently does.

Reviewers: rnk, MaskRay, aganea, hans, espindola, jhenderson

Subscribers: jholewinski, qcolombet, dschuff, jyknight, emaste, sdardis, nemanjai, jvesely, nhaehnle, sbc100, jgravelle-google, hiraditya, aheejin, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, jrtc27, zzheng, edward-jones, atanasyan, steven_wu, rogfer01, MartinMosbeck, brucehoult, the_o, dexonsmith, PkmX, rupprecht, jocewei, jsji, Jim, dmgreen, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, kerbowa, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D74456
2020-02-11 18:20:40 -08:00
Gabor Horvath
fe44f75159 [LTO] Add optimization remarks for removed functions
This only works with regular LTO for now.

Differential Revision: https://reviews.llvm.org/D73597
2020-01-29 15:53:51 -08:00
Yuanfang Chen
b1c09bbef0 Revert "[Support] make report_fatal_error abort instead of exit"
This reverts commit 647c3f4e47de8a850ffcaa897db68702d8d2459a.

Got bots failure from sanitizer-windows and maybe others.
2020-01-15 17:52:25 -08:00
Yuanfang Chen
725cd0da61 [Support] make report_fatal_error abort instead of exit
Summary:
This patch could be treated as a rebase of D33960. It also fixes PR35547.
A fix for `llvm/test/Other/close-stderr.ll` is proposed in D68164. Seems
the consensus is that the test is passing by chance and I'm not
sure how important it is for us. So it is removed like in D33960 for now.
The rest of the test fixes are just adding `--crash` flag to `not` tool.

** The reason it fixes PR35547 is

`exit` does cleanup including calling class destructor whereas `abort`
does not do any cleanup. In multithreading environment such as ThinLTO or JIT,
threads may share states which mostly are ManagedStatic<>. If faulting thread
tearing down a class when another thread is using it, there are chances of
memory corruption. This is bad 1. It will stop error reporting like pretty
stack printer; 2. The memory corruption is distracting and nondeterministic in
terms of error message, and corruption type (depending one the timing, it
could be double free, heap free after use, etc.).

Reviewers: rnk, chandlerc, zturner, sepavloff, MaskRay, espindola

Reviewed By: rnk, MaskRay

Subscribers: wuzish, jholewinski, qcolombet, dschuff, jyknight, emaste, sdardis, nemanjai, jvesely, nhaehnle, sbc100, arichardson, jgravelle-google, aheejin, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, jsji, lenary, s.egerton, pzheng, cfe-commits, MaskRay, filcab, davide, MatzeB, mehdi_amini, hiraditya, steven_wu, dexonsmith, rupprecht, seiya, llvm-commits

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D67847
2020-01-15 17:05:13 -08:00
James Henderson
91705af363 [NFC] Fix trivial typos in comments
Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D72143

Patch by Kazuaki Ishizaki.
2020-01-06 10:50:26 +00:00
Fangrui Song
8e823f1246 [llvm-nm] Display STT_GNU_IFUNC as 'i'
Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D71803
2019-12-25 09:47:53 -08:00
Fangrui Song
d9c5df08b1 Migrate function attribute "no-frame-pointer-elim" to "frame-pointer"="all" as cleanups after D56351 2019-12-24 15:57:33 -08:00
Teresa Johnson
3a2a2bb628 [LTO] Support for embedding bitcode section during LTO
Summary:
This adds support for embedding bitcode in a binary during LTO. The libLTO gains supports the `-lto-embed-bitcode` flag. The option allows users of the LTO library to embed a bitcode section. For example, LLD can pass the option via `ld.lld -mllvm=-lto-embed-bitcode`.

This feature allows doing something comparable to `clang -c -fembed-bitcode`, but on the (LTO) linker level. Having bitcode alongside native code has many use-cases. To give an example, the MacOS linker can create a `-bitcode_bundle` section containing bitcode. Also, having this feature built into LLVM is an alternative to 3rd party tools such as [[ https://github.com/travitch/whole-program-llvm | wllvm ]] or [[ https://github.com/SRI-CSL/gllvm | gllvm ]]. As with these tools, this feature simplifies creating "whole-program" llvm bitcode files, but in contrast to wllvm/gllvm it does not rely on a specific llvm frontend/driver.

Patch by Josef Eisl <josef.eisl@oracle.com>

Reviewers: #llvm, #clang, rsmith, pcc, alexshap, tejohnson

Reviewed By: tejohnson

Subscribers: tejohnson, mehdi_amini, inglorion, hiraditya, aheejin, steven_wu, dexonsmith, dang, cfe-commits, llvm-commits, #llvm, #clang

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D68213
2019-12-12 12:34:19 -08:00
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
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
Pirama Arumuga Nainar
96d22d6fc4 [IRMover] Don't map globals if their types are the same
Summary:
During IR Linking, if the types of two globals in destination and source
modules are the same, it can only be because the global in the
destination module is originally from the source module and got added to
the destination module from a shared metadata.

We shouldn't map this type to itself in case the type's components get
remapped to a new type from the destination (for instance, during the
loop over SrcM->getIdentifiedStructTypes() further below in
IRLinker::computeTypeMapping()).

Fixes PR40312.

Reviewers: tejohnson, pcc, srhines

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66814

llvm-svn: 371643
2019-09-11 18:35:49 +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
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
Manoj Gupta
6592a4fc99 Revert r369233.
This breaks building of some projects like libfuse and alsa-lib
that now fail when linking.
Error details in PR43092.

llvm-svn: 369790
2019-08-23 18:01:13 +00:00
Teresa Johnson
749908c114 Fix target for new X86 test
Test added in r369766 had the wrong target arch for the X86 directory,
leading to some bot failures. Fix it to have the appropriate target.

llvm-svn: 369774
2019-08-23 16:02:25 +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
Fangrui Song
d2dba26b00 [MC] Don't emit .symver redirected symbols to the symbol table
GNU as keeps the original symbol in the symbol table for defined @ and
@@, but suppresses it in other cases (@@@ or undefined). The original
symbol is usually undesired:
In a shared object, the original symbol can be localized with a version
script, but it is hard to remove/localize in an archive:

1) a post-processing step removes the undesired original symbol
2) consumers (executable) of the archive are built with the
   version script

Moreover, it can cause linker issues like binutils PR/18703 if the
original symbol name and the base name of the versioned symbol is the
same (both ld.bfd and gold have some code to work around defined @ and
@@). In lld, if it sees f and f@v1:

  --version-script =(printf 'v1 {};') => f and f@v1
  --version-script =(printf 'v1 { f; };') => f@v1 and f@@v1

It can be argued that @@@ added on 2000-11-13 corrected the @ and @@ mistake.

This patch catches some more multiple version errors (defined @ and @@),
and consistently suppress the original symbol. This addresses all the
problems listed above.

If the user wants other aliases to the versioned symbol, they can copy
the original symbol to other symbol names with .set directive, e.g.

    .symver f, f@v1  # emit f@v1 but not f into .symtab
    .set f_impl, f   # emit f_impl into .symtab

llvm-svn: 369233
2019-08-19 06:17:30 +00:00
Peter Collingbourne
c349d0b828 Linker: Add support for GlobalIFunc.
GlobalAlias and GlobalIFunc ought to be treated the same by the IR
linker, so we can generalize the code to be in terms of their common
base class GlobalIndirectSymbol.

Differential Revision: https://reviews.llvm.org/D55046

llvm-svn: 368357
2019-08-08 22:09:18 +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
Johannes Doerfert
1f3d696f06 [NFC] Adjust "invalid.ll.bc" tests to check for AttrKind #255 not #63
We are about to add enum attributes with AttrKind numbers >= 63. This
means we cannot use AttrKind #63 to test for an invalid attribute number
in the RAW format anymore. This patch changes the number of an invalid
attribute to #255. There is no change to the character of the tests.

Differential Revision: https://reviews.llvm.org/D64531

llvm-svn: 365722
2019-07-11 01:14:30 +00:00
Jordan Rupprecht
3ef3977b58 Revert [InlineCost] cleanup calculations of Cost and Threshold
This reverts r364422 (git commit 1a3dc761860d620ac8ed7e32a4285952142f780b)

The inlining cost calculation is incorrect, leading to stack overflow due to large stack frames from heavy inlining.

llvm-svn: 365000
2019-07-03 04:01:51 +00:00
Fedor Sergeev
2f54ed60d2 [InlineCost] cleanup calculations of Cost and Threshold
Summary:
Doing better separation of Cost and Threshold.
Cost counts the abstract complexity of live instructions, while Threshold is an upper bound of complexity that inlining is comfortable to pay.
There are two parts:
     - huge 15K last-call-to-static bonus is no longer subtracted from Cost
       but rather is now added to Threshold.

       That makes much more sense, as the cost of inlining (Cost) is not changed by the fact
       that internal function is called once. It only changes the likelyhood of this inlining
       being profitable (Threshold).

     - bonus for calls proved-to-be-inlinable into callee is no longer subtracted from Cost
       but added to Threshold instead.

While calculations are somewhat different,  overall InlineResult should stay the same since Cost >= Threshold compares the same.

Reviewers: eraman, greened, chandlerc, yrouban, apilipenko
Reviewed By: apilipenko
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60740

llvm-svn: 364422
2019-06-26 13:24:24 +00:00
Ben Dunbobbin
33ef399ccf [ThinLTO]LTO]Legacy] Fix dependent libraries support by adding querying of the IRSymtab
Dependent libraries support for the legacy api was committed in a
broken state (see: https://reviews.llvm.org/D60274). This was missed
due to the painful nature of having to integrate the changes into a
linker in order to test. This change implements support for dependent
libraries in the legacy LTO api:

- I have removed the current api function, which returns a single
string, and   added functions to access each dependent library
specifier individually.

- To reduce the testing pain, I have made the api functions as thin as
possible to   maximize coverage from llvm-lto.

- When doing ThinLTO the system linker will load the modules lazily
when scanning   the input files. Unfortunately, when modules are
lazily loaded there is no access   to module level named metadata. To
fix this I have added api functions that allow   querying the IRSymtab
for the dependent libraries. I hope to expand the api in the   future
so that, eventually, all the information needed by a client linker
during   scan can be retrieved from the IRSymtab.

Differential Revision: https://reviews.llvm.org/D62935

llvm-svn: 363140
2019-06-12 11:07:56 +00:00
Ben Dunbobbin
2aa2767ebe [ELF] Implement Dependent Libraries Feature
This patch implements a limited form of autolinking primarily designed to allow
either the --dependent-library compiler option, or "comment lib" pragmas (
https://docs.microsoft.com/en-us/cpp/preprocessor/comment-c-cpp?view=vs-2017) in
C/C++ e.g. #pragma comment(lib, "foo"), to cause an ELF linker to automatically
add the specified library to the link when processing the input file generated
by the compiler.

Currently this extension is unique to LLVM and LLD. However, care has been taken
to design this feature so that it could be supported by other ELF linkers.

The design goals were to provide:

- A simple linking model for developers to reason about.
- The ability to to override autolinking from the linker command line.
- Source code compatibility, where possible, with "comment lib" pragmas in other
  environments (MSVC in particular).

Dependent library support is implemented differently for ELF platforms than on
the other platforms. Primarily this difference is that on ELF we pass the
dependent library specifiers directly to the linker without manipulating them.
This is in contrast to other platforms where they are mapped to a specific
linker option by the compiler. This difference is a result of the greater
variety of ELF linkers and the fact that ELF linkers tend to handle libraries in
a more complicated fashion than on other platforms. This forces us to defer
handling the specifiers to the linker.

In order to achieve a level of source code compatibility with other platforms
we have restricted this feature to work with libraries that meet the following
"reasonable" requirements:

1. There are no competing defined symbols in a given set of libraries, or
   if they exist, the program owner doesn't care which is linked to their
   program.
2. There may be circular dependencies between libraries.

The binary representation is a mergeable string section (SHF_MERGE,
SHF_STRINGS), called .deplibs, with custom type SHT_LLVM_DEPENDENT_LIBRARIES
(0x6fff4c04). The compiler forms this section by concatenating the arguments of
the "comment lib" pragmas and --dependent-library options in the order they are
encountered. Partial (-r, -Ur) links are handled by concatenating .deplibs
sections with the normal mergeable string section rules. As an example, #pragma
comment(lib, "foo") would result in:

.section ".deplibs","MS",@llvm_dependent_libraries,1
         .asciz "foo"

For LTO, equivalent information to the contents of a the .deplibs section can be
retrieved by the LLD for bitcode input files.

LLD processes the dependent library specifiers in the following way:

1. Dependent libraries which are found from the specifiers in .deplibs sections
   of relocatable object files are added when the linker decides to include that
   file (which could itself be in a library) in the link. Dependent libraries
   behave as if they were appended to the command line after all other options. As
   a consequence the set of dependent libraries are searched last to resolve
   symbols.
2. It is an error if a file cannot be found for a given specifier.
3. Any command line options in effect at the end of the command line parsing apply
   to the dependent libraries, e.g. --whole-archive.
4. The linker tries to add a library or relocatable object file from each of the
   strings in a .deplibs section by; first, handling the string as if it was
   specified on the command line; second, by looking for the string in each of the
   library search paths in turn; third, by looking for a lib<string>.a or
   lib<string>.so (depending on the current mode of the linker) in each of the
   library search paths.
5. A new command line option --no-dependent-libraries tells LLD to ignore the
   dependent libraries.

Rationale for the above points:

1. Adding the dependent libraries last makes the process simple to understand
   from a developers perspective. All linkers are able to implement this scheme.
2. Error-ing for libraries that are not found seems like better behavior than
   failing the link during symbol resolution.
3. It seems useful for the user to be able to apply command line options which
   will affect all of the dependent libraries. There is a potential problem of
   surprise for developers, who might not realize that these options would apply
   to these "invisible" input files; however, despite the potential for surprise,
   this is easy for developers to reason about and gives developers the control
   that they may require.
4. This algorithm takes into account all of the different ways that ELF linkers
   find input files. The different search methods are tried by the linker in most
   obvious to least obvious order.
5. I considered adding finer grained control over which dependent libraries were
   ignored (e.g. MSVC has /nodefaultlib:<library>); however, I concluded that this
   is not necessary: if finer control is required developers can fall back to using
   the command line directly.

RFC thread: http://lists.llvm.org/pipermail/llvm-dev/2019-March/131004.html.

Differential Revision: https://reviews.llvm.org/D60274

llvm-svn: 360984
2019-05-17 03:44:15 +00:00
Fangrui Song
28e82b6565 [llvm-readobj] Change -t to --symbols in tests. NFC
-t is --symbols in llvm-readobj but --section-details (unimplemented) in readelf.
The confusing option should not be used since we aim for improving
compatibility.

Keep just one llvm-readobj -t use case in test/tools/llvm-readobj/symbols.test

llvm-svn: 359661
2019-05-01 09:28:24 +00:00
Fangrui Song
9e863883e1 [llvm-nm][llvm-readelf] Avoid single-dash -long-option in tests
llvm-svn: 359383
2019-04-27 16:12:14 +00:00
Steven Wu
e757d7f8e8 Revert [ThinLTO] Fix ThinLTOCodegenerator to export llvm.used symbols
This reverts r357931 (git commit 8b70a5c11e08116955a875b9085433f14737bcaf)

llvm-svn: 357932
2019-04-08 18:53:21 +00:00
Steven Wu
9ddbd54259 [ThinLTO] Fix ThinLTOCodegenerator to export llvm.used symbols
Summary:
ThinLTOCodeGenerator currently does not preserve llvm.used symbols and
it can internalize them. In order to pass the necessary information to the
legacy ThinLTOCodeGenerator, the input to the code generator is
rewritten to be based on lto::InputFile.

This fixes: PR41236
rdar://problem/49293439

Reviewers: tejohnson, pcc, dexonsmith

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, eraman, hiraditya, jkorous, dang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60226

llvm-svn: 357931
2019-04-08 18:24:10 +00:00
Rafael Auler
086f86be13 [Linker] Fix crash handling appending linkage
Summary:
When linking two llvm.used arrays, if the resulting merged
array ends up with duplicated elements (with the same name) but with
different types, the IRLinker was crashing. This was supposed to be
legal, as the IRLinker bitcasts elements to match types in these
situations.

This bug was exposed by D56928 in clang to support attribute used
in member functions of class templates. Crash happened when self-hosting
with LTO. Since LLVM depends on attribute used to generate code
for the dump() method, ubiquitous in the code base, many input bc
had a definition of this method referenced in their llvm.used array.
Some of these classes got optimized, changing the type of the first
parameter (this) in the dump method, leading to a scenario with a
pool of valid definitions but some with a different type, triggering
this bug.

This is a memory bug: ValueMapper depends on (calls) the materializer
provided by IRLinker, and this materializer was freely calling RAUW
methods whenever a global definition was updated in the temporary merged
output file. However, replaceAllUsesWith may or may not destroy
constants that use this global. If the linked definition has a type
mismatch regarding the new def and the old def, the materializer would
bitcast the old type to the new type and the elements of the llvm.used
array, which already uses bitcast to i8*, would end up with elements
cascading two bitcasts. RAUW would then indirectly call the
constantfolder to update the constant to the new ref, which would,
instead of updating the constant, destroy it to be able to create
a new constant that folds the two bitcasts into one. The problem is that
ValueMapper works with pointers to the same constants that may be
getting destroyed by RAUW. Obviously, RAUW can update references in the
Module to do not use the old destroyed constant, but it can't update
ValueMapper's internal pointers to these constants, which are now
invalid.

The approach here is to move the task of RAUWing old definitions
outside of the materializer.

Test Plan:
Added LIT test case, tested clang self-hosting with D56928 and
verified it works

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D59552

llvm-svn: 356597
2019-03-20 19:20:07 +00:00
Robert Lougher
46e12bc5ef Resubmit r356511 "[TailCallElim] Add tailcall elimination pass to LTO pipelines"
Failing LLD tests have been fixed in r356593.

llvm-svn: 356594
2019-03-20 19:08:18 +00:00
Robert Lougher
a0c4fb1375 Revert r356511 "[TailCallElim] Add tailcall elimination pass to LTO pipelines"
Due to buildbot failures (LLD tests).

llvm-svn: 356516
2019-03-19 20:54:20 +00:00
Robert Lougher
0f1b915264 [TailCallElim] Add tailcall elimination pass to LTO pipelines
LTO provides additional opportunities for tailcall elimination due to
link-time inlining and visibility of nocapture attribute. Testing showed
negligible impact on compilation times.

Differential Revision: https://reviews.llvm.org/D58391

llvm-svn: 356511
2019-03-19 20:24:28 +00:00
Francis Visoiu Mistrih
14e47fc8be Reland "[Remarks] Add -foptimization-record-passes to filter remark emission"
Currently we have -Rpass for filtering the remarks that are displayed as
diagnostics, but when using -fsave-optimization-record, there is no way
to filter the remarks while generating them.

This adds support for filtering remarks by passes using a regex.
Ex: `clang -fsave-optimization-record -foptimization-record-passes=inline`

will only emit the remarks coming from the pass `inline`.

This adds:

* `-fsave-optimization-record` to the driver
* `-opt-record-passes` to cc1
* `-lto-pass-remarks-filter` to the LTOCodeGenerator
* `--opt-remarks-passes` to lld
* `-pass-remarks-filter` to llc, opt, llvm-lto, llvm-lto2
* `-opt-remarks-passes` to gold-plugin

Differential Revision: https://reviews.llvm.org/D59268

Original llvm-svn: 355964

llvm-svn: 355984
2019-03-12 21:22:27 +00:00
Matt Arsenault
01d726ce5c IR: Add immarg attribute
This indicates an intrinsic parameter is required to be a constant,
and should not be replaced with a non-constant value.

Add the attribute to all AMDGPU and generic intrinsics that comments
indicate it should apply to. I scanned other target intrinsics, but I
don't see any obvious comments indicating which arguments are intended
to be only immediates.

This breaks one questionable testcase for the autoupgrade. I'm unclear
on whether the autoupgrade is supposed to really handle declarations
which were never valid. The verifier fails because the attributes now
refer to a parameter past the end of the argument list.

llvm-svn: 355981
2019-03-12 21:02:54 +00:00
Francis Visoiu Mistrih
b72c67b1b1 Revert "[Remarks] Add -foptimization-record-passes to filter remark emission"
This reverts commit 20fff32b7d1f1a1bd417b22aa9f26ededd97a3e5.

llvm-svn: 355976
2019-03-12 20:54:18 +00:00
Francis Visoiu Mistrih
5fb25c63d5 [Remarks] Add -foptimization-record-passes to filter remark emission
Currently we have -Rpass for filtering the remarks that are displayed as
diagnostics, but when using -fsave-optimization-record, there is no way
to filter the remarks while generating them.

This adds support for filtering remarks by passes using a regex.
Ex: `clang -fsave-optimization-record -foptimization-record-passes=inline`

will only emit the remarks coming from the pass `inline`.

This adds:

* `-fsave-optimization-record` to the driver
* `-opt-record-passes` to cc1
* `-lto-pass-remarks-filter` to the LTOCodeGenerator
* `--opt-remarks-passes` to lld
* `-pass-remarks-filter` to llc, opt, llvm-lto, llvm-lto2
* `-opt-remarks-passes` to gold-plugin

Differential Revision: https://reviews.llvm.org/D59268

llvm-svn: 355964
2019-03-12 20:28:50 +00:00
Teresa Johnson
52c19ef944 [LTO] Record whether LTOUnit splitting is enabled in index
Summary:
Records in the module summary index whether the bitcode was compiled
with the option necessary to enable splitting the LTO unit
(e.g. -fsanitize=cfi, -fwhole-program-vtables, or -fsplit-lto-unit).

The information is passed down to the ModuleSummaryIndex builder via a
new module flag "EnableSplitLTOUnit", which is propagated onto a flag
on the summary index.

This is then used during the LTO link to check whether all linked
summaries were built with the same value of this flag. If not, an error
is issued when we detect a situation requiring whole program visibility
of the class hierarchy. This is the case when both of the following
conditions are met:
1) We are performing LowerTypeTests or Whole Program Devirtualization.
2) There are type tests or type checked loads in the code.

Note I have also changed the ThinLTOBitcodeWriter to also gate the
module splitting on the value of this flag.

Reviewers: pcc

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

Differential Revision: https://reviews.llvm.org/D53890

llvm-svn: 350948
2019-01-11 18:31:57 +00:00
Matthew Voss
ef16314d07 [ThinLTO] Remove dllimport attribute from locally defined symbols
Summary:
The LTO/ThinLTO driver currently creates invalid bitcode by setting 
symbols marked dllimport as dso_local. The compiler often has access 
to the definition (often dllexport) and the declaration (often 
dllimport) of an object at link-time, leading to a conflicting 
declaration. This patch resolves the inconsistency by removing the
dllimport attribute.

Reviewers: tejohnson, pcc, rnk, echristo

Reviewed By: rnk

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

Differential Revision: https://reviews.llvm.org/D55627

llvm-svn: 349667
2018-12-19 19:07:45 +00:00
Peter Collingbourne
fe3c1d8a1b LTO: Don't internalize available_externally globals.
This breaks C and C++ semantics because it can cause the address
of the global inside the module to differ from the address outside
of the module.

Differential Revision: https://reviews.llvm.org/D55237

llvm-svn: 348321
2018-12-05 00:09:36 +00:00