dso_local leads to direct access even if the definition is not within this compilation unit (it is
still in the same linkage unit). On ELF, such a relocation (e.g. R_X86_64_PC32) referencing a
STB_GLOBAL STV_DEFAULT object can cause a linker error in a -shared link.
If the linkage is changed to available_externally, the dso_local flag should be dropped, so that no
direct access will be generated.
The current behavior is benign, because -fpic does not assume dso_local
(clang/lib/CodeGen/CodeGenModule.cpp:shouldAssumeDSOLocal).
If we do that for -fno-semantic-interposition (D73865), there will be an
R_X86_64_PC32 linker error without this patch.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D74751
Summary:
D69561/dde5893 enabled importing of readonly variables with references,
however, it introduced a bug relating to importing/internalization of
writeonly variables with references.
A fix for this was added in D70006/7f92d66. But this didn't work in
distributed ThinLTO mode. The reason is that the fix (importing the
writeonly var with a zeroinitializer) was only applied when there were
references on the writeonly var summary. In distributed ThinLTO mode,
where we only have a small slice of the index, we will not have the
references on the importing side if we are not importing those
referenced values. Rather than changing this handshaking (which will
require a lot of other changes, since that's how we know what to import
in the distributed backend clang invocation), we can simply always give
the writeonly variable a zero initializer.
Reviewers: evgeny777, steven_wu
Subscribers: mehdi_amini, inglorion, hiraditya, dexonsmith, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70977
Summary:
Pass down the already accessed ValueInfo to shouldPromoteLocalToGlobal,
to avoid an unnecessary extra index lookup.
Add some assertion checking to confirm we have a non-empty VI when
expected.
Also some misc cleanup, merging the two versions of
doImportAsDefinition, since one was only called by the other, and
unnecessarily passed in a member variable.
Reviewers: steven_wu, pcc, evgeny777
Reviewed By: evgeny777
Subscribers: mehdi_amini, inglorion, hiraditya, dexonsmith, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70337
Summary:
Clean up the code that does GV promotion in the ThinLTO backends.
Specifically, we don't need to check whether we are importing since that
is already checked and handled correctly in shouldPromoteLocalToGlobal.
Simply call shouldPromoteLocalToGlobal, and if it returns true we are
guaranteed that we are promoting, whether or not we are importing (or in
the exporting module). This also makes the handling in getName()
consistent with that in getLinkage(), which checks the DoPromote parameter
regardless of whether we are importing or exporting.
Reviewers: steven_wu, pcc, evgeny777
Subscribers: mehdi_amini, inglorion, hiraditya, dexonsmith, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70327
ValueInfo has user-defined 'operator bool' which allows incorrect implicit conversion
to GlobalValue::GUID (which is unsigned long). This causes bugs which are hard to
track and should be removed in future.
This patch adds an assertion check for exported read/write-only
variables to be also in import list for module. If they aren't
we may face linker errors, because read/write-only variables are
internalized in their source modules. The patch also changes
export lists to store ValueInfo instead of GUID for performance
considerations.
Differential revision: https://reviews.llvm.org/D70128
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
Patch allows importing declarations of functions and variables, referenced
by the initializer of some other readonly variable.
Differential revision: https://reviews.llvm.org/D69561
This recommits cc0b9647b7 which was
reverted in d39d1a2f87.
I added a fix for an issue found when testing via distributed ThinLTO,
and added a test case for that failure.
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
The static analyzer is warning about a potential null dereference, but we should be able to use cast<FunctionSummary> directly and if not assert will fire for us.
llvm-svn: 373097
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
This reverts r365040 (git commit 5cacb91475)
Speculatively reverting, since this appears to have broken check-lld on
Linux. Partial analysis in https://crbug.com/981168.
llvm-svn: 365097
Summary:
COFF requires that COMDAT name match that of the leader. When we promote
and rename an internal leader in ThinLTO due to an import, ensure we
subsequently rename the associated COMDAT. Similar to D31963 which did
this during ThinLTO module splitting.
Fixes PR40414.
Reviewers: pcc, inglorion
Subscribers: mehdi_amini, dexonsmith, dmajor, llvm-commits
Differential Revision: https://reviews.llvm.org/D57395
llvm-svn: 352763
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
Summary:
This patch computes the synthetic function entry count on the whole
program callgraph (based on module summary) and writes the entry counts
to the summary. After function importing, this count gets attached to
the IR as metadata. Since it adds a new field to the summary, this bumps
up the version.
Reviewers: tejohnson
Subscribers: mehdi_amini, inglorion, llvm-commits
Differential Revision: https://reviews.llvm.org/D43521
llvm-svn: 349076
Summary:
This is a NFC as we do not import non-odr vague linkage when computing
for import list for a module.
Reviewers: tejohnson, pcc
Subscribers: inglorion, dexonsmith, llvm-commits
Differential Revision: https://reviews.llvm.org/D54928
llvm-svn: 347763
An attempt to recommit r346584 after failure on OSX build bot.
Fixed cache key computation in ThinLTOCodeGenerator and added
test case
llvm-svn: 347033
This patch allows internalising globals if all accesses to them
(from live functions) are from non-volatile load instructions
Differential revision: https://reviews.llvm.org/D49362
llvm-svn: 346584
This is PR36686.
If a user of a library is LTOed with that library we take the
opportunity to set dso_local, but we don't clear dllimport, which
creates an invalid IR.
llvm-svn: 327408
Now that we have a way to mark GlobalValues as local we can use the symbol
resolutions that the linker plugin provides as part of lto/thinlto link
step to refine the compilers view on what symbols will end up being local.
Originally commited as r317374, but reverted in r317395 to update some missed
tests.
Differential Revision: https://reviews.llvm.org/D35702
llvm-svn: 317408
Now that we have a way to mark GlobalValues as local we can use the symbol
resolutions that the linker plugin provides as part of lto/thinlto link
step to refine the compilers view on what symbols will end up being local.
Differential Revision: https://reviews.llvm.org/D35702
llvm-svn: 317374
Summary:
Until a more advanced version of importing can be implemented for
aliases (one that imports an alias as an available_externally definition
of the aliasee), skip the narrow subset of cases that was possible but
came at a cost: aliases of linkonce_odr functions could be imported
because the linkonce_odr function could be safely duplicated from the
source module. This came/comes at the cost of not being able to 'home'
imported linkonce functions (they had to be emitted linkonce_odr in all
the destination modules (even if they weren't used by an alias) rather
than as available_externally - causing extra object size).
Tangentially, this also was the only reason ThinLTO would emit multiple
CUs in to the resulting DWARF - which happens to be a problem for
Fission (there's a fix for this in GDB but not released yet, etc).
(actually it's not the only reason - but I'm sending a patch to fix the
other reason shortly)
There's no reason to believe this particularly narrow alias importing
was especially/meaningfully important, only that it was /possible/ to
implement in this way. When a more general solution is done, it should
still satisfy the DWARF concerns above, since the import will still be
available_externally, and thus not create extra CUs.
Since now all aliases are treated the same, I removed/simplified some
test cases since they were testing corner cases where there are no
longer any corners.
Reviewers: tejohnson, mehdi_amini
Differential Revision: https://reviews.llvm.org/D35875
llvm-svn: 309278
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.
I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.
This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.
Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).
llvm-svn: 304787
The importer was previously using ModuleLinker in a sort of "IRMover mode". Use
IRMover directly instead in order to remove a level of indirection.
I will remove all importing support from ModuleLinker in a separate
change.
Differential Revision: https://reviews.llvm.org/D29468
llvm-svn: 294014
Summary:
r285871 introduced an assert that was overly aggressive in the case
of a same-named local in different same-named files (in different
directories), where the source name and therefore the GUID ended up
the same because the files were compiled in their own directory without
any leading path. Change the handling in the promotion logic to get
the summary for the version in that module.
This also exposed an issue where we are not always importing the
right copy, which is a performance not correctness issue (because
the renaming is based on the module hash which must be different,
see the bug report for details). I will fix that as a follow-on.
Fixes PR31561.
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D28411
llvm-svn: 291304
Summary:
This adds a new summary flag NotEligibleToImport that subsumes
several existing flags (NoRename, HasInlineAsmMaybeReferencingInternal
and IsNotViableToInline). It also subsumes the checking of references
on the summary that was being done during the thin link by
eligibleForImport() for each candidate. It is much more efficient to
do that checking once during the per-module summary build and record
it in the summary.
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D28169
llvm-svn: 291108
Summary:
We were doing an optimization in the ThinLTO backends of importing
constant unnamed_addr globals unconditionally as a local copy (regardless
of whether the thin link decided to import them). This should be done in
the thin link instead, so that resulting exported references are marked
and promoted appropriately, but will need a summary enhancement to mark
these variables as constant unnamed_addr.
The function import logic during the thin link was trying to handle
this proactively, by conservatively marking all values referenced in
the initializer lists of exported global variables as also exported.
However, this only handled values referenced directly from the
initializer list of an exported global variable. If the value is itself
a constant unnamed_addr variable, we could end up exporting its
references as well. This caused multiple issues. The first is that the
transitively exported references weren't promoted. Secondly, some could
not be promoted/renamed (e.g. they had a section or other constraint).
recursively, instead of just adding the first level of initializer list
references to the ExportList directly.
Remove this optimization and the associated handling in the function
import backend. SPEC measurements indicate we weren't getting much
from it in any case.
Fixes PR31052.
Reviewers: mehdi_amini
Subscribers: krasin, llvm-commits
Differential Revision: https://reviews.llvm.org/D26880
llvm-svn: 288446
Summary:
We have always speculatively promoted all renamable local values
(except const non-address taken variables) for both the exporting
and importing module. We would then internalize them back based on
the ThinLink results if they weren't actually exported. This is
inefficient, and results in unnecessary renames. It also meant we
had to check the non-renamability of a value in the summary, which
was already checked during function importing analysis in the ThinLink.
Made renameModuleForThinLTO (which does the promotion/renaming) instead
use the index when exporting, to avoid unnecessary renames/promotions.
For importing modules, we can simply promoted all values as any local
we import by definition is exported and needs promotion.
This required changes to the method used by the FunctionImport pass
(only invoked from 'opt' for testing) and when invoked from llvm-link,
since neither does a ThinLink. We simply conservatively mark all locals
in the index as promoted, which preserves the current aggressive
promotion behavior.
I also needed to change an llvm-lto based test where we had previously
been aggressively promoting values that weren't importable (aliasees),
but now will not promote.
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D26467
llvm-svn: 286871
Summary:
The recent change I made to consult the summary when deciding whether to
rename (to handle inline asm) in r285513 broke the distributed build
case. In a distributed backend we will only have a portion of the
combined index, specifically for imported modules we only have the
summaries for any imported definitions. When renaming on import we were
asserting because no summary entry was found for a local reference being
linked in (def wasn't imported).
We only need to consult the summary for a renaming decision for the
exporting module. For imports, we would have prevented importing any
references to NoRename values already.
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D26250
llvm-svn: 285871
Summary:
Instead of using the workaround of suppressing the entire index for
modules that call inline asm that may reference locals, use the
NoRename flag on the summary for any locals in the llvm.used set, and
add a reference edge from any functions containing inline asm.
This avoids issues from having no summaries despite the module defining
global values, which was preventing more aggressive index-based
optimization. It will be followed by a subsequent patch to make a
similar fix for local references in module level asm (to fix PR30610).
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D26121
llvm-svn: 285513
Summary:
Replace the check of whether a GV has a section with the flag check
in the summary. This is in preparation for using the NoPromote flag
to convey other situations when we can't promote (e.g. locals used in
inline asm).
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D26063
llvm-svn: 285507
If a local_unnamed_addr attribute is attached to a global, the address
is known to be insignificant within the module. It is distinct from the
existing unnamed_addr attribute in that it only describes a local property
of the module rather than a global property of the symbol.
This attribute is intended to be used by the code generator and LTO to allow
the linker to decide whether the global needs to be in the symbol table. It is
possible to exclude a global from the symbol table if three things are true:
- This attribute is present on every instance of the global (which means that
the normal rule that the global must have a unique address can be broken without
being observable by the program by performing comparisons against the global's
address)
- The global has linkonce_odr linkage (which means that each linkage unit must have
its own copy of the global if it requires one, and the copy in each linkage unit
must be the same)
- It is a constant or a function (which means that the program cannot observe that
the unique-address rule has been broken by writing to the global)
Although this attribute could in principle be computed from the module
contents, LTO clients (i.e. linkers) will normally need to be able to compute
this property as part of symbol resolution, and it would be inefficient to
materialize every module just to compute it.
See:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.htmlhttp://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html
for earlier discussion.
Part of the fix for PR27553.
Differential Revision: http://reviews.llvm.org/D20348
llvm-svn: 272709
This test was crashing, and currently it breaks bootstrapping clang with debuginfo
Differential Revision: http://reviews.llvm.org/D20008
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 268715
Summary:
Refine the workaround from r266877 that attempts to prevent
renaming of locals in inline assembly, so that in addition to looking
for a llvm.used local value, that there is at least one inline assembly
call in the module. Otherwise, debug functions added to the llvm.used
can block importing/exporting unnecessarily.
Reviewers: joker.eph
Subscribers: llvm-commits, joker.eph
Differential Revision: http://reviews.llvm.org/D19573
llvm-svn: 267717
Fangrui Song