rather than two callbacks.
The asynchronous lookup API (which the synchronous lookup API wraps for
convenience) used to take two callbacks: OnResolved (called once all requested
symbols had an address assigned) and OnReady to be called once all requested
symbols were safe to access). This patch updates the asynchronous lookup API to
take a single 'OnComplete' callback and a required state (SymbolState) to
determine when the callback should be made. This simplifies the common use case
(where the client is interested in a specific state) and will generalize neatly
as new states are introduced to track runtime initialization of symbols.
Clients who were making use of both callbacks in a single query will now need to
issue two queries (one for SymbolState::Resolved and another for
SymbolState::Ready). Synchronous lookup API clients who were explicitly passing
the WaitOnReady argument will now need neeed to pass a SymbolState instead (for
'WaitOnReady == true' use SymbolState::Ready, for 'WaitOnReady == false' use
SymbolState::Resolved). Synchronous lookup API clients who were using default
arugment values should see no change.
llvm-svn: 362832
Summary:
This was flagged in https://www.viva64.com/en/b/0629/ under "Snippet No.
33".
It seems that this statement is doing the standard bitwise trick for
adjusting a value to have a specific alignment.
The issue is that getStubAlignment() returns an unsigned, while DataSize
is declared a uint64_t. The right hand side of the expression is not
extended to 64b before bitwise negation, resulting in the top half of
the mask being 0s, which is not correct for realignment.
Reviewers: lhames, MaskRay
Reviewed By: MaskRay
Subscribers: RKSimon, MaskRay, hiraditya, llvm-commits, srhines
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D62227
llvm-svn: 362286
increase the MachO/x86-64 stub alignment to 8.
Stub alignment should be guaranteed for any section containing RuntimeDyld
stubs/GOT-entries. To do this we should pad and align all sections containing
stubs, not just code sections.
This commit also bumps the MachO/x86-64 stub alignment to 8, so that GOT entries
will be aligned.
llvm-svn: 362139
Prior to this patch, JITDylibs inferred symbol states (whether a symbol was
newly added, materializing, resolved, or ready to run) via a combination of (1)
bits in the JITSymbolFlags member, and (2) the state of some internal JITDylib
data structures. This patch explicitly tracks symbol states by adding a new
SymbolState member to the symbol table entries, and removing the 'Lazy' and
'Materializing' bits from JITSymbolFlags. This is a first step towards adding
additional states representing initialization phases (e.g. eh-frame registration,
registration with the language runtime, and static initialization).
llvm-svn: 361899
Summary:
EH Frames aren't supported on AIX with the system compiler, but the definition of HAVE_EHTABLE_SUPPORT misses this which causes linking problems on AIX. This patch updates the definition of HAVE_EHTABLE_SUPPORT in both JITLink and RuntimeDyld.
Author: daltenty
Reviewers: sfertile, xingxue, hubert.reinterpretcase
Reviewed By: xingxue
Subscribers: hiraditya, jsji, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D62203
llvm-svn: 361410
Summary:
scan-build flagged a potential use-after-move in debug builds. It's not
safe that a moved from value contains anything but garbage. Manually
DRY up these repeated expressions.
Reviewers: lhames
Reviewed By: lhames
Subscribers: hiraditya, llvm-commits, srhines
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D62112
llvm-svn: 361203
Rename member 'Size' to 'AllocatedSize' in order to provide a hint that the
allocated size may be different than the requested size. Comments are added to
clarify this point. Updated the InMemoryBuffer in FileOutputBuffer.cpp to track
the requested buffer size.
Patch by Machiel van Hooren. Thanks Machiel!
https://reviews.llvm.org/D61599
llvm-svn: 361195
SymbolStringPtr used to use nullptr as its empty value and (since it performed
ref-count operations on any non-nullptr) a pointer to a special pool-entry
instance as its tombstone.
This commit changes the scheme to use two invalid pointer values as the empty
and tombstone values, and broadens the ref-count guard to prevent ref-counting
operations from being performed on these pointers. This should improve the
performance of SymbolStringPtrs used in DenseMaps/DenseSets, as ref counting
operations will no longer be performed on the tombstone.
llvm-svn: 360925
r360876 didn't fix 2 call sites in clang.
Expected<ArrayRef<uint8_t>> may be better but use Expected<StringRef> for now.
Follow-up of D61781.
llvm-svn: 360892
It broke the Clang build, see llvm-commits thread.
> Expected<ArrayRef<uint8_t>> may be better but use Expected<StringRef> for now.
>
> Follow-up of D61781.
llvm-svn: 360878
Fixes a think-o. No test case: The nlist and nlist64 data structures happen to
line up for this field, so there's no way to construct a failing test case.
llvm-svn: 360830
Previously we had only honored alignments on individual atoms, but
tools/runtimes may assume that the section alignment is respected too.
llvm-svn: 360555
Also updates RuntimeDyldChecker and llvm-rtdyld to support zero-fill tests by
returning a content address of zero (but no error) for zero-fill atoms, and
treating loads from zero as returning zero.
llvm-svn: 360547
If a MachO section has the no-dead-strip attribute set then its atoms should
be preserved, regardless of whether they're public or referenced elsewhere in
the object.
llvm-svn: 360477
Subtractor relocation addends are signed, so we need to read them via signed
int pointers. Accidentally treating 32-bit addends as unsigned leads to
out-of-range errors when we try to add very large (>INT32_MAX) bogus addends.
llvm-svn: 360392
Adds full edge details (rather than just edge targets) when out-of-range errors
are generated. Also fixes a bug where debugging output accessed an invalidated
DenseMap iterator by moving the debugging output above the invalidation point.
llvm-svn: 360383
Commit r360221 ("[Support] Add error handling to
sys::Process::getPageSize().", 2019-05-08) seems to have missed these
uses of getPageSize(). Update them to getPageSizeEstimate().
llvm-svn: 360322
This patch changes the return type of sys::Process::getPageSize to
Expected<unsigned> to account for the fact that the underlying syscalls used to
obtain the page size may fail (see below).
For clients who use the page size as an optimization only this patch adds a new
method, getPageSizeEstimate, which calls through to getPageSize but discards
any error returned and substitues a "reasonable" page size estimate estimate
instead. All existing LLVM clients are updated to call getPageSizeEstimate
rather than getPageSize.
On Unix, sys::Process::getPageSize is implemented in terms of getpagesize or
sysconf, depending on which macros are set. The sysconf call is documented to
return -1 on failure. On Darwin getpagesize is implemented in terms of sysconf
and may also fail (though the manpage documentation does not mention this).
These failures have been observed in practice when highly restrictive sandbox
permissions have been applied. Without this patch, the result is that
getPageSize returns -1, which wreaks havoc on any subsequent code that was
assuming a sane page size value.
<rdar://problem/41654857>
Reviewers: dblaikie, echristo
Subscribers: kristina, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59107
llvm-svn: 360221
This patch modifies MachOAtomGraphBuilder to use setLayoutNext rather than
addEdge, and fixes a bug in the section layout algorithm that could result in
atoms appearing more than once in the section ordering (which resulted in those
atoms being assigned invalid addresses during layout).
llvm-svn: 360205
The MachO .alt_entry directive is applied to a symbol to indicate that it is
locked (in terms of address layout and liveness) to its predecessor atom. I.e.
it is an alternate entry point, at a fixed offset, for the previous atom.
This patch updates MachOAtomGraphBuilder to check for the .alt_entry flag on
symbols and add a corresponding LayoutNext edge to the atom-graph. It also
updates MachOAtomGraphBuilder_x86_64 to generalize handling of the
X86_64_RELOC_SUBTRACTOR relocation: previously either the minuend or
subtrahend of the subtraction had to be the same as the atom being fixed up,
now it is only necessary for the minuend or subtrahend to be locked (via any
chain of alt_entry directives) to the atom being fixed up.
llvm-svn: 360194
These operations were already used in eh-frame registration, and are likely to
be used in other runtime registrations, so this commit moves them into a header
where they can be re-used.
llvm-svn: 359950
Clients who want to regain ownership of object buffers after they have been
linked may now use the NotifyEmitted callback for this purpose.
Note: Currently NotifyEmitted is only called if linking succeeds. If linking
fails the buffer is always discarded.
llvm-svn: 359735
JITLinkGeneric phases 2 and 3 (focused on applying fixups and finalizing memory,
respectively) may fail for various reasons. If this happens, we need to
explicitly de-allocate the memory allocated in phase 1 (explicitly, because
deallocation may also fail and so is implemented as a method returning error).
No testcase yet: I am still trying to decide on the right way to test totally
platform agnostic code like this.
llvm-svn: 359643
In-memory compiled object buffer identifiers will now be derived from the
identifiers of their source IR modules. This makes it easier to connect
in-memory objects with their source modules in debugging output.
llvm-svn: 359613
Background: A definition generator can be attached to a JITDylib to generate
new definitions in response to queries. For example: a generator that forwards
calls to dlsym can map symbols from a dynamic library into the JIT process on
demand.
If definition generation fails then the generator should be able to return an
error. This allows the JIT API to distinguish between the case where a
generator does not provide a definition, and the case where it was not able to
determine whether it provided a definition due to an error.
The immediate motivation for this is cross-process symbol lookups: If the
remote-lookup generator is attached to a JITDylib early in the search list, and
if a generator failure is misinterpreted as "no definition in this JITDylib" then
lookup may continue and bind to a different definition in a later JITDylib, which
is a bug.
llvm-svn: 359521
LLJITBuilder and LLLazyJITBuilder construct LLJIT and LLLazyJIT instances
respectively. Over time these will allow more configurable options to be
added while remaining easy to use in the default case, which for default
in-process JITing is now:
auto J = ExitOnErr(LLJITBuilder.create());
llvm-svn: 359511
ObjectLinkingLayer::Plugin provides event notifications when objects are loaded,
emitted, and removed. It also provides a modifyPassConfig callback that allows
plugins to modify the JITLink pass configuration.
This patch moves eh-frame registration into its own plugin, and teaches
llvm-jitlink to only add that plugin when performing execution runs on
non-Windows platforms. This should allow us to re-enable the test case that was
removed in r359198.
llvm-svn: 359357
When failing materialization of a symbol X, remove X from the dependants list
of any of X's dependencies. This ensures that when X's dependencies are
emitted (or fail themselves) they do not try to access the no-longer-existing
MaterializationInfo for X.
llvm-svn: 359252
Frame Descriptor Entries (FDEs) have a pointer back to a Common Information
Entry (CIE) that describes how the rest FDE should be parsed. JITLink had been
assuming that FDEs always referred to the most recent CIE encountered, but the
spec allows them to point back to any previously encountered CIE. This patch
fixes JITLink to look up the correct CIE for the FDE.
The testcase is a MachO binary with an FDE that refers to a CIE that is not the
one immediately proceeding it (the layout can be viewed wit
'dwarfdump --eh-frame <testcase>'. This test case had to be a binary as llvm-mc
now sorts FDEs (as of r356216) to ensure FDEs *do* point to the most recent CIE.
llvm-svn: 359105
Section atoms are not sorted, so we need to scan the whole section to find the
start address.
No test case: Found by inspection, and any reproduction would depend on pointer
ordering.
llvm-svn: 358865
The error check required FDEs to refer to the most recent CIE, but the eh-frame
spec allows them to refer to any previously seen CIE. This patch removes the
offending check.
llvm-svn: 358840
Knowing the address/symbolnum field values makes it easier to identify the
unsupported relocation, and provides enough information for the full bit
pattern of the relocation to be reconstructed.
llvm-svn: 358833
Summary:
JITLink is a jit-linker that performs the same high-level task as RuntimeDyld:
it parses relocatable object files and makes their contents runnable in a target
process.
JITLink aims to improve on RuntimeDyld in several ways:
(1) A clear design intended to maximize code-sharing while minimizing coupling.
RuntimeDyld has been developed in an ad-hoc fashion for a number of years and
this had led to intermingling of code for multiple architectures (e.g. in
RuntimeDyldELF::processRelocationRef) in a way that makes the code more
difficult to read, reason about, extend. JITLink is designed to isolate
format and architecture specific code, while still sharing generic code.
(2) Support for native code models.
RuntimeDyld required the use of large code models (where calls to external
functions are made indirectly via registers) for many of platforms due to its
restrictive model for stub generation (one "stub" per symbol). JITLink allows
arbitrary mutation of the atom graph, allowing both GOT and PLT atoms to be
added naturally.
(3) Native support for asynchronous linking.
JITLink uses asynchronous calls for symbol resolution and finalization: these
callbacks are passed a continuation function that they must call to complete the
linker's work. This allows for cleaner interoperation with the new concurrent
ORC JIT APIs, while still being easily implementable in synchronous style if
asynchrony is not needed.
To maximise sharing, the design has a hierarchy of common code:
(1) Generic atom-graph data structure and algorithms (e.g. dead stripping and
| memory allocation) that are intended to be shared by all architectures.
|
+ -- (2) Shared per-format code that utilizes (1), e.g. Generic MachO to
| atom-graph parsing.
|
+ -- (3) Architecture specific code that uses (1) and (2). E.g.
JITLinkerMachO_x86_64, which adds x86-64 specific relocation
support to (2) to build and patch up the atom graph.
To support asynchronous symbol resolution and finalization, the callbacks for
these operations take continuations as arguments:
using JITLinkAsyncLookupContinuation =
std::function<void(Expected<AsyncLookupResult> LR)>;
using JITLinkAsyncLookupFunction =
std::function<void(const DenseSet<StringRef> &Symbols,
JITLinkAsyncLookupContinuation LookupContinuation)>;
using FinalizeContinuation = std::function<void(Error)>;
virtual void finalizeAsync(FinalizeContinuation OnFinalize);
In addition to its headline features, JITLink also makes other improvements:
- Dead stripping support: symbols that are not used (e.g. redundant ODR
definitions) are discarded, and take up no memory in the target process
(In contrast, RuntimeDyld supported pointer equality for weak definitions,
but the redundant definitions stayed resident in memory).
- Improved exception handling support. JITLink provides a much more extensive
eh-frame parser than RuntimeDyld, and is able to correctly fix up many
eh-frame sections that RuntimeDyld currently (silently) fails on.
- More extensive validation and error handling throughout.
This initial patch supports linking MachO/x86-64 only. Work on support for
other architectures and formats will happen in-tree.
Differential Revision: https://reviews.llvm.org/D58704
llvm-svn: 358818
This patch reduces the number of functions in the interface between RuntimeDyld
and RuntimeDyldChecker by combining "GetXAddress" and "GetXContent" functions
into "GetXInfo" functions that return a struct describing both the address and
content. The GetStubOffset function is also replaced with a pair of utilities,
GetStubInfo and GetGOTInfo, that fit the new scheme. For RuntimeDyld both of
these functions will return the same result, but for the new JITLink linker
(https://reviews.llvm.org/D58704) these will provide the addresses of PLT stubs
and GOT entries respectively.
For JITLink's use, a 'got_addr' utility has been added to the rtdyld-check
language, and the syntax of 'got_addr' and 'stub_addr' has been changed: both
functions now take two arguments, a 'stub container name' and a target symbol
name. For llvm-rtdyld/RuntimeDyld the stub container name is the object file
name and section name, separated by a slash. E.g.:
rtdyld-check: *{8}(stub_addr(foo.o/__text, y)) = y
For the upcoming llvm-jitlink utility, which creates stubs on a per-file basis
rather than a per-section basis, the container name is just the file name. E.g.:
jitlink-check: *{8}(got_addr(foo.o, y)) = y
llvm-svn: 358295
Following r354972 the Intel JIT Listener would not report line table
information because the section indices did not match. There was
a similar issue with the PerfJitEventListener. This change performs
the section index lookup when building the object address used to
query the line table information.
Differential Revision: https://reviews.llvm.org/D59490
llvm-svn: 356895
When running lli --debug --force-interpreter=true the executed instructions are
printed but are missing newlines. This commit adds the missing newlines.
Patch by Andrew Brown.
Differential Revision: https://reviews.llvm.org/D57806
llvm-svn: 355587
This cleans up all LoadInst creation in LLVM to explicitly pass the
value type rather than deriving it from the pointer's element-type.
Differential Revision: https://reviews.llvm.org/D57172
llvm-svn: 352911
This cleans up all CallInst creation in LLVM to explicitly pass a
function type rather than deriving it from the pointer's element-type.
Differential Revision: https://reviews.llvm.org/D57170
llvm-svn: 352909
ELF sections allow 0 for the alignment, which is specified to
be the same as 1. However many clients do not expect this and
will behave poorly in the presence of a 0-aligned section (for
example by trying to modulo something by the section alignment).
We can be more polite by making sure that we always pass a
non-zero value to clients.
Differential Revision: https://reviews.llvm.org/D57482
llvm-svn: 352694
This patch tried to address the following use case.
. bcc (https://github.com/iovisor/bcc) utilizes llvm JIT to
compile for BTF target.
. with -g, .BTF and .BTF.ext sections (BPF debug info)
will be generated by LLVM.
. .BTF does not have relocations and .BTF.ext has some
relocations.
. With ProcessAllSections, .BTF.ext is loaded by JIT dynamic linker
and is available to application. But .BTF is not loaded.
The bcc application needs both .BTF.ext and .BTF for debugging
purpose, and .BTF is not loaded. This patch addressed this issue
by iterating over all sections and loading any missing
sections, after symbol/relocation processing in loadObjectImpl().
Signed-off-by: Yonghong Song <yhs@fb.com>
Differential Revision: https://reviews.llvm.org/D55943
llvm-svn: 352432
Previously, MemoryBlock automatically extends a requested buffer size to a
multiple of page size because (I believe) doing it was thought to be harmless
and with that you could get more memory (on average 2KiB on 4KiB-page systems)
"for free".
That programming interface turned out to be error-prone. If you request N
bytes, you usually expect that a resulting object returns N for `size()`.
That's not the case for MemoryBlock.
Looks like there is only one place where we take the advantage of
allocating more memory than the requested size. So, with this patch, I
simply removed the automatic size expansion feature from MemoryBlock
and do it on the caller side when needed. MemoryBlock now always
returns a buffer whose size is equal to the requested size.
Differential Revision: https://reviews.llvm.org/D56941
llvm-svn: 351916
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
This will allow other utilities (including a future RuntimeDyld replacement) to
use these types without pulling in the major Core types (JITDylib, etc.).
llvm-svn: 351138
MIPS `jr` instruction uses a delay-slot. To escape execution of
arbitrary instruction we should either fill the delay-slot by `nop`
instruction or swap `jr` instruction and logically preceding
instruction. This fix implements the second method to generate a bit
more effective code.
llvm-svn: 351001
MIPS ABI states that every function must be called through jalr $t9. In
other words, a function expect that t9 register points to the beginning
of its code. A function uses this register to calculate offset to the
Global Offset Table and save it to the `gp` register.
```
lui $gp, %hi(_gp_disp)
addiu $gp, %lo(_gp_disp)
addu $gp, $gp, $t9
```
If `t9` and as a result `$gp` point to the wrong place the following code
loads incorrect value from GOT and passes control to invalid code.
```
lw $v0,%call16(foo)($gp)
jalr $t9
```
OrcMips32 and OrcMips64 writeResolverCode methods pass control to the
resolved address, but do not setup `$t9` before the call. The `t9` holds
value of the beginning of `resolver` code so any attempts to call
routines via GOT failed.
This change fixes the problem. The `OrcLazy/hidden-visibility.ll` test
starts to pass correctly. Before the change it fails on MIPS because the
`exitOnLazyCallThroughFailure` called from the resolver code could not
call libc routine `exit` via GOT.
Differential Revision: http://reviews.llvm.org/D56058
llvm-svn: 351000
That is, remove many of the calls to Type::getNumContainedTypes(),
Type::subtypes(), and Type::getContainedType(N).
I'm not intending to remove these accessors -- they are
useful/necessary in some cases. However, removing the pointee type
from pointers would potentially break some uses, and reducing the
number of calls makes it easier to audit.
llvm-svn: 350835
lldb on Windows uses the ExecutionEngine for expression evaluation
and hits the llvm_unreachable due to this relocation. Thus, implement
the relocation and add a test to verify it's function.
llvm-svn: 348904
This patch renames both methods (NotifyObjectEmitted -> notifyObjectLoaded, and
NotifyObjectFreed -> notifyObjectFreed), adds an abstract "ObjectKey" (uint64_t)
parameter to notifyObjectLoaded, and replaces the ObjectFile parameter for
notifyObjectFreed with an ObjectKey. Using an ObjectKey to track identify
events, rather than a reference to the ObjectFile, allows us to free the
ObjectFile after notifyObjectLoaded is called, saving memory.
https://reviews.llvm.org/D53773
llvm-svn: 348223
In a lot of places an empty string was passed as the ErrorBanner to
logAllUnhandledErrors. This patch makes that argument optional to
simplify the call sites.
llvm-svn: 346604
Doesn't build on Windows. The call to 'lookup' is ambiguous. Clang and
MSVC agree, anyway.
http://lab.llvm.org:8011/builders/clang-x64-windows-msvc/builds/787
C:\b\slave\clang-x64-windows-msvc\build\llvm.src\unittests\ExecutionEngine\Orc\CoreAPIsTest.cpp(315): error C2668: 'llvm::orc::ExecutionSession::lookup': ambiguous call to overloaded function
C:\b\slave\clang-x64-windows-msvc\build\llvm.src\include\llvm/ExecutionEngine/Orc/Core.h(823): note: could be 'llvm::Expected<llvm::JITEvaluatedSymbol> llvm::orc::ExecutionSession::lookup(llvm::ArrayRef<llvm::orc::JITDylib *>,llvm::orc::SymbolStringPtr)'
C:\b\slave\clang-x64-windows-msvc\build\llvm.src\include\llvm/ExecutionEngine/Orc/Core.h(817): note: or 'llvm::Expected<llvm::JITEvaluatedSymbol> llvm::orc::ExecutionSession::lookup(const llvm::orc::JITDylibSearchList &,llvm::orc::SymbolStringPtr)'
C:\b\slave\clang-x64-windows-msvc\build\llvm.src\unittests\ExecutionEngine\Orc\CoreAPIsTest.cpp(315): note: while trying to match the argument list '(initializer list, llvm::orc::SymbolStringPtr)'
llvm-svn: 345078
In the new scheme the client passes a list of (JITDylib&, bool) pairs, rather
than a list of JITDylibs. For each JITDylib the boolean indicates whether or not
to match against non-exported symbols (true means that they should be found,
false means that they should not). The MatchNonExportedInJD and MatchNonExported
parameters on lookup are removed.
The new scheme is more flexible, and easier to understand.
This patch also updates JITDylib search orders to be lists of (JITDylib&, bool)
pairs to match the new lookup scheme. Error handling is also plumbed through
the LLJIT class to allow regression tests to fail predictably when a lookup from
a lazy call-through fails.
llvm-svn: 345077
Non-loaded sections (whose unused load-address defaults to zero) should not
be taken into account when calculating ImageBase, or ImageBase will be
incorrectly set to 0.
Patch by Andrew Scheidecker. Thanks Andrew!
https://reviews.llvm.org/D51343
+ // The Sections list may contain sections that weren't loaded for
+ // whatever reason: they may be debug sections, and ProcessAllSections
+ // is false, or they may be sections that contain 0 bytes. If the
+ // section isn't loaded, the load address will be 0, and it should not
+ // be included in the ImageBase calculation.
llvm-svn: 344995
Otherwise we can end up with a data-race when linking concurrently.
This should fix an intermittent failure in the multiple-compile-threads-basic.ll
testcase.
llvm-svn: 344956
MaterializationResponsibility.
VModuleKeys are intended to enable selective removal of modules from a JIT
session, however for a wide variety of use cases selective removal is not
needed and introduces unnecessary overhead. As of this commit, the default
constructed VModuleKey value is reserved as a "do not track" value, and
becomes the default when adding a new module to the JIT.
This commit also changes the propagation of VModuleKeys. They were passed
alongside the MaterializationResponsibity instance in XXLayer::emit methods,
but are now propagated as part of the MaterializationResponsibility instance
itself (and as part of MaterializationUnit when stored in a JITDylib).
Associating VModuleKeys with MaterializationUnits in this way should allow
for a thread-safe module removal mechanism in the future, even when a module
is in the process of being compiled, by having the
MaterializationResponsibility object check in on its VModuleKey's state
before commiting its results to the JITDylib.
llvm-svn: 344643
This commit adds a 'Legacy' prefix to old ORC layers and utilities, and removes
the '2' suffix from the new ORC layers. If you wish to continue using the old
ORC layers you will need to add a 'Legacy' prefix to your classes. If you were
already using the new ORC layers you will need to drop the '2' suffix.
The legacy layers will remain in-tree until the new layers reach feature
parity with them. This will involve adding support for removing code from the
new layers, and ensuring that performance is comperable.
llvm-svn: 344572
The new name is a better fit: This class does not actually spawn any new
threads for compilation, it is just safe to call from multiple threads
concurrently.
The "Simple" part of the name did not convey much either, so it was
dropped.
llvm-svn: 344567
Renames:
JITDylib's setFallbackDefinitionGenerator method to setGenerator.
DynamicLibraryFallbackGenerator class to DynamicLibrarySearchGenerator.
ReexportsFallbackDefinitionGenerator to ReexportsGenerator.
llvm-svn: 344489
This adds two arguments to the main ExecutionSession::lookup method:
MatchNonExportedInJD, and MatchNonExported. These control whether and where
hidden symbols should be matched when searching a list of JITDylibs.
A similar effect could have been achieved by filtering search results, but
this would have involved materializing symbol definitions (since materialization
is triggered on lookup) only to throw the results away, among other issues.
llvm-svn: 344467
rather than require them to have been promoted before being passed in.
Dropping this precondition is better for layer composition (CompileOnDemandLayer
was the only one that placed pre-conditions on the modules that could be added).
It also means that the promoted private symbols do not show up in the target
JITDylib's symbol table. Instead, they are confined to the hidden implementation
dylib that contains the actual definitions.
For the 403.gcc testcase this cut down the public symbol table size from ~15,000
symbols to ~4000, substantially reducing symbol dependence tracking costs.
llvm-svn: 344078
Symbols can be removed provided that all are present in the JITDylib and none
are currently in the materializing state. On success all requested symbols are
removed. On failure an error is returned and no symbols are removed.
llvm-svn: 343928
(1) Adds comments for the API.
(2) Removes the setArch method: This is redundant: the setArchStr method on the
triple should be used instead.
(3) Turns EmulatedTLS on by default. This matches EngineBuilder's behavior.
llvm-svn: 343423
CompileOnDemandLayer2 now supports user-supplied partition functions (the
original CompileOnDemandLayer already supported these).
Partition functions are called with the list of requested global values
(i.e. global values that currently have queries waiting on them) and have an
opportunity to select extra global values to materialize at the same time.
Also adds testing infrastructure for the new feature to lli.
llvm-svn: 343396
This makes it available for use in IRTransformLayer2::TransformFunction
instances (since a const MaterializationResponsibility& parameter was
added in r343365).
llvm-svn: 343367
(1) A const accessor for the LLVMContext held by a ThreadSafeContext.
(2) A const accessor for the ThreadSafeModules held by an IRMaterializationUnit.
(3) A const MaterializationResponsibility reference to IRTransformLayer2's
transform function. This makes IRTransformLayer2 useful for JIT debugging
(since it can inspect JIT state through the responsibility argument) as well
as program transformations.
llvm-svn: 343365
(1) Print debugging output under a session lock to avoid garbled messages when
compiling on multiple threads.
(2) Name MaterializationUnits, add an ostream operator for them, and so they can
be easily referenced in debugging output, and have that ostream operator
optionally print code/data/hidden symbols provided by that materialization unit
based on command line options.
llvm-svn: 343323
flag to true in LLJIT when running in multithreaded mode.
The IRLayer::setCloneToNewContextOnEmit method sets a flag within the IRLayer
that causes modules added to that layer to be moved to a new context (by
serializing to/from a memory buffer) when they are emitted. This allows modules
that were all loaded on the same context to be compiled in parallel.
llvm-svn: 343266
one SymbolLinkagePromoter utility.
SymbolLinkagePromoter renames anonymous and private symbols, and bumps all
linkages to at least global/hidden-visibility. Modules whose symbols have been
promoted by this utility can be decomposed into sub-modules without introducing
link errors. This is used by the CompileOnDemandLayer to extract single-function
modules for lazy compilation.
llvm-svn: 343257
Modifies lit to add a 'thread_support' feature that can be used in lit test
REQUIRES clauses. The thread_support flag is set if -DLLVM_ENABLE_THREADS=ON
and unset if -DLLVM_ENABLE_THREADS=OFF. The lit flag is used to disable the
multiple-compile-threads-basic.ll testcase when threading is disabled.
llvm-svn: 343122
This doesn't work well in builds configured with LLVM_ENABLE_THREADS=OFF,
causing the following assert when running
ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll:
lib/ExecutionEngine/Orc/Core.cpp:1748: Expected<llvm::JITEvaluatedSymbol>
llvm::orc::lookup(const llvm::orc::JITDylibList &, llvm::orc::SymbolStringPtr):
Assertion `ResultMap->size() == 1 && "Unexpected number of results"' failed.
> LLJIT and LLLazyJIT can now be constructed with an optional NumCompileThreads
> arguments. If this is non-zero then a thread-pool will be created with the
> given number of threads, and compile tasks will be dispatched to the thread
> pool.
>
> To enable testing of this feature, two new flags are added to lli:
>
> (1) -compile-threads=N (N = 0 by default) controls the number of compile threads
> to use.
>
> (2) -thread-entry can be used to execute code on additional threads. For each
> -thread-entry argument supplied (multiple are allowed) a new thread will be
> created and the given symbol called. These additional thread entry points are
> called after static constructors are run, but before main.
llvm-svn: 343099
for lazy compilation, rather than a callback manager.
The new mechanism does not block compile threads, and does not require
function bodies to be renamed.
Future modifications should allow laziness on a per-module basis to work
without any modification of the input module.
llvm-svn: 343065
implementation as lazy compile callbacks, and a "lazy re-exports" utility that
builds lazy call-throughs.
Lazy call-throughs are similar to lazy compile callbacks (and are based on the
same underlying state saving/restoring trampolines) but resolve their targets
by performing a standard ORC lookup rather than invoking a user supplied
compiler callback. This allows them to inherit the thread-safety of ORC lookups
while blocking only the calling thread (whereas compile callbacks also block one
compile thread).
Lazy re-exports provide a simple way of building lazy call-throughs. Unlike a
regular re-export, a lazy re-export generates a new address (a stub entry point)
that will act like the re-exported symbol when called. The first call via a
lazy re-export will trigger compilation of the re-exported symbol before calling
through to it.
llvm-svn: 343061
This will allow trampoline pools to be re-used for a new lazy-reexport utility
that generates looks up function bodies using the standard symbol lookup process
(rather than using a user provided compile function). This new utility provides
the same capabilities (since MaterializationUnits already allow user supplied
compile functions to be run) as JITCompileCallbackManager, but can use the new
asynchronous lookup functions to avoid blocking a compile thread.
This patch also updates createLocalCompileCallbackManager to return an error if
a callback manager can not be created, and updates clients of that API to
account for the change. Finally, the OrcCBindingsStack is updates so that if
a callback manager is not available for the target platform a valid stack
(without support for lazy compilation) can still be constructed.
llvm-svn: 343059
LLJIT and LLLazyJIT can now be constructed with an optional NumCompileThreads
arguments. If this is non-zero then a thread-pool will be created with the
given number of threads, and compile tasks will be dispatched to the thread
pool.
To enable testing of this feature, two new flags are added to lli:
(1) -compile-threads=N (N = 0 by default) controls the number of compile threads
to use.
(2) -thread-entry can be used to execute code on additional threads. For each
-thread-entry argument supplied (multiple are allowed) a new thread will be
created and the given symbol called. These additional thread entry points are
called after static constructors are run, but before main.
llvm-svn: 343058
compilation of IR in the JIT.
ThreadSafeContext is a pair of an LLVMContext and a mutex that can be used to
lock that context when it needs to be accessed from multiple threads.
ThreadSafeModule is a pair of a unique_ptr<Module> and a
shared_ptr<ThreadSafeContext>. This allows the lifetime of a ThreadSafeContext
to be managed automatically in terms of the ThreadSafeModules that refer to it:
Once all modules using a ThreadSafeContext are destructed, and providing the
client has not held on to a copy of shared context pointer, the context will be
automatically destructed.
This scheme is necessary due to the following constraits: (1) We need multiple
contexts for multithreaded compilation (at least one per compile thread plus
one to store any IR not currently being compiled, though one context per module
is simpler). (2) We need to free contexts that are no longer being used so that
the JIT does not leak memory over time. (3) Module lifetimes are not
predictable (modules are compiled as needed depending on the flow of JIT'd
code) so there is no single point where contexts could be reclaimed.
JIT clients not using concurrency can safely use one ThreadSafeContext for all
ThreadSafeModules.
JIT clients who want to be able to compile concurrently should use a different
ThreadSafeContext for each module, or call setCloneToNewContextOnEmit on their
top-level IRLayer. The former reduces compile latency (since no clone step is
needed) at the cost of additional memory overhead for uncompiled modules (as
every uncompiled module will duplicate the LLVM types, constants and metadata
that have been shared).
llvm-svn: 343055
switch RTDyldObjectLinkingLayer2 to use it.
RuntimeDyld::loadObject is currently a blocking operation. This means that any
JIT'd code whose call-graph contains an embedded complete K graph will require
at least K threads to link, which precludes the use of a fixed sized thread
pool for concurrent JITing of arbitrary code (whatever K the thread-pool is set
at, any code with a K+1 complete subgraph will deadlock at JIT-link time).
To address this issue, this commmit introduces a function called jitLinkForORC
that uses continuation-passing style to pass the fix-up and finalization steps
to the asynchronous symbol resolver interface so that linking can be performed
without blocking.
llvm-svn: 343043
This reverts commit r342939.
MSVC's promise/future implementation does not like types that are not default
constructible. Reverting while I figure out a solution.
llvm-svn: 342941
Asynchronous resolution (where the caller receives a callback once the requested
set of symbols are resolved) is a core part of the new concurrent ORC APIs. This
change extends the asynchronous resolution model down to RuntimeDyld, which is
necessary to prevent deadlocks when compiling/linking on a fixed number of
threads: If RuntimeDyld's linking process were a blocking operation, then any
complete K-graph in a program will require at least K threads to link in the
worst case, as each thread would block waiting for all the others to complete.
Using callbacks instead allows the work to be passed between dependent threads
until it is complete.
For backwards compatibility, all existing RuntimeDyld functions will continue
to operate in blocking mode as before. This change will enable the introduction
of a new async finalization process in a subsequent patch to enable asynchronous
JIT linking.
llvm-svn: 342939
This replaces instances of the LLVMOrcErrorCode type with LLVMErrorRef,
simplifying the implementation of the OrcCBindingsStack class and ORC
C API bindings and making it possible to return arbitrary (wrapped)
llvm::Errors.
llvm-svn: 342828
template methods in JITDylib out-of-line.
This also splits JITDylib::define into a pair of template methods, one taking an
lvalue reference and the other an rvalue reference. This simplifies the
templates at the cost of a small amount of code duplication.
llvm-svn: 342087
construction, a new convenience lookup method, and add-to layer methods.
ExecutionSession now creates a special 'main' JITDylib upon construction. All
subsequently created JITDylibs are added to the main JITDylib's search order by
default (controlled by the AddToMainDylibSearchOrder parameter to
ExecutionSession::createDylib). The main JITDylib's search order will be used in
the future to properly handle cross-JITDylib weak symbols, with the first
definition in this search order selected.
This commit also adds a new ExecutionSession::lookup convenience method that
performs a blocking lookup using the main JITDylib's search order, as this will
be a very common operation for clients.
Finally, new convenience overloads of IRLayer and ObjectLayer's add methods are
introduced that add the given program representations to the main dylib, which
is likely to be the common case.
llvm-svn: 342086
This patch adds support for ORC JIT for mips/mips64 architecture.
In common code $static is changed to __ORCstatic because on MIPS
architecture "$" is a reserved character.
Patch by Luka Ercegovcevic
Differential Revision: https://reviews.llvm.org/D49665
llvm-svn: 341934
The existing memory manager API can not be shared between objects when linking
concurrently (since there is no way to know which concurrent allocations were
performed on behalf of which object, and hence which allocations would be safe
to finalize when finalizeMemory is called). For now, we can work around this by
requiring a new memory manager for each object.
This change only affects the concurrent version of the ORC APIs.
llvm-svn: 341579
Section address mappings can be applied using the RuntimeDyld instance passed to
the RuntimeDyld::MemoryManager::notifyObjectLoaded method. Proving an alternate
route via RuntimeDyldObjectLinkingLayer2 is redundant.
llvm-svn: 341578
Removes the implicit conversion to the underlying type for
JITSymbolFlags::FlagNames and replaces it with some bitwise and comparison
operators.
llvm-svn: 341282
management and materialization responsibility registration.
The setOverrideObjectFlagsWithResponsibilityFlags method instructs
RTDyldObjectlinkingLayer2 to override the symbol flags produced by RuntimeDyld with
the flags provided by the MaterializationResponsibility instance. This can be used
to enable symbol visibility (hidden/exported) for COFF object files, which do not
currently support the SF_Exported flag.
The setAutoClaimResponsibilityForObjectSymbols method instructs
RTDyldObjectLinkingLayer2 to claim responsibility for any symbols provided by a
given object file that were not already in the MaterializationResponsibility
instance. Setting this flag allows higher-level program representations (e.g.
LLVM IR) to be added based on only a subset of the symbols they provide, without
having to write intervening layers to scan and add the additional symbols. This
trades diagnostic quality for convenience however: If all symbols are enumerated
up-front then clashes can be detected and reported early. If this option is set,
clashes for the additional symbols may not be detected until late, and detection
may depend on the flow of control through JIT'd code.
llvm-svn: 341154
The new method name/behavior more closely models the way it was being used.
It also fixes an assertion that can occur when using the new ORC Core APIs,
where flags alone don't necessarily provide enough context to decide whether
the caller is responsible for materializing a given symbol (which was always
the reason this API existed).
The default implementation of getResponsibilitySet uses lookupFlags to determine
responsibility as before, so existing JITSymbolResolvers should continue to
work.
llvm-svn: 340874
The addObjectFile method adds the given object file to the JIT session, making
its code available for execution.
Support for the -extra-object flag is added to lli when operating in
-jit-kind=orc-lazy mode to support testing of this feature.
llvm-svn: 340870
Private symbols are not visible outside the object file, and so not defined by
the object file from ORC's perspective.
No test case yet. Ideally this would be a unit test parsing a checked-in binary,
but I am not aware of any way to reference the LLVM source root from a unit
test.
llvm-svn: 340703
An emitted symbol has had its contents written and its memory protections
applied, but it is not automatically ready to execute.
Prior to ORC supporting concurrent compilation, the term "finalized" could be
interpreted two different (but effectively equivalent) ways: (1) The finalized
symbol's contents have been written and its memory protections applied, and (2)
the symbol is ready to run. Now that ORC supports concurrent compilation, sense
(1) no longer implies sense (2). We have already introduced a new term, 'ready',
to capture sense (2), so rename sense (1) to 'emitted' to avoid any lingering
confusion.
llvm-svn: 340115
VSO was a little close to VDSO (an acronym on Linux for Virtual Dynamic Shared
Object) for comfort. It also risks giving the impression that instances of this
class could be shared between ExecutionSessions, which they can not.
JITDylib seems moderately less confusing, while still hinting at how this
class is intended to be used, i.e. as a JIT-compiled stand-in for a dynamic
library (code that would have been a dynamic library if you had wanted to
compile it ahead of time).
llvm-svn: 340084
MCJIT::getSymbolAddress was handling a non-fatal error condition of JITSymbol
as fatal. JITSymbol::operator bool returns false if no address is available
but no error is set. This can occur e.g. if the symbol name was not found.
Patch by Jascha Wetzel. Thanks Jascha!
llvm-svn: 339809
This code was moved out from BasicObjectLayerMaterializationUnit, which required
the supplied object to be well formed. The getObjectSymbolFlags function does
not require a well-formed object, so we have to propagate the error here.
llvm-svn: 338975
An instance of ReexportsFallbackDefinitionGenerator can be attached to a VSO
(via setFallbackDefinitionGenerator) to re-export symbols on demandy from a
backing VSO.
llvm-svn: 338764
The callable flag can be used to indicate that a symbol is callable. If present,
the symbol is callable. If absent, the symbol may or may not be callable (the
client must determine this by context, for example by examining the program
representation that will provide the symbol definition).
This flag will be used in the near future to enable creation of lazy compilation
stubs based on SymbolFlagsMap instances only (without having to provide
additional information to determine which symbols need stubs).
llvm-svn: 338649
Initially, in https://reviews.llvm.org/D44890, I had these defined as
empty functions inside the header when the respective event listener
was not built in. As done in that commit, that wasn't correct, because
it was a ODR violation. Krasimir hot-fixed that in r333265, but that
wasn't quite right either, because it'd lead to the symbol not being
available.
Instead just move the fallbacksto ExecutionEngineBindings.cpp. Could
define them as static inlines in the header too, but I don't think it
matters.
Reviewers: whitequark
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D49654
llvm-svn: 337930
This new JIT event listener supports generating profiling data for
the linux 'perf' profiling tool, allowing it to generate function and
instruction level profiles.
Currently this functionality is not enabled by default, but must be
enabled with LLVM_USE_PERF=yes. Given that the listener has no
dependencies, it might be sensible to enable by default once the
initial issues have been shaken out.
I followed existing precedent in registering the listener by default
in lli. Should there be a decision to enable this by default on linux,
that should probably be changed.
Please note that until https://reviews.llvm.org/D47343 is resolved,
using this functionality with mcjit rather than orcjit will not
reliably work.
Disregarding the previous comment, here's an example:
$ cat /tmp/expensive_loop.c
bool stupid_isprime(uint64_t num)
{
if (num == 2)
return true;
if (num < 1 || num % 2 == 0)
return false;
for(uint64_t i = 3; i < num / 2; i+= 2) {
if (num % i == 0)
return false;
}
return true;
}
int main(int argc, char **argv)
{
int numprimes = 0;
for (uint64_t num = argc; num < 100000; num++)
{
if (stupid_isprime(num))
numprimes++;
}
return numprimes;
}
$ clang -ggdb -S -c -emit-llvm /tmp/expensive_loop.c -o
/tmp/expensive_loop.ll
$ perf record -o perf.data -g -k 1 ./bin/lli -jit-kind=mcjit /tmp/expensive_loop.ll 1
$ perf inject --jit -i perf.data -o perf.jit.data
$ perf report -i perf.jit.data
- 92.59% lli jitted-5881-2.so [.] stupid_isprime
stupid_isprime
main
llvm::MCJIT::runFunction
llvm::ExecutionEngine::runFunctionAsMain
main
__libc_start_main
0x4bf6258d4c544155
+ 0.85% lli ld-2.27.so [.] do_lookup_x
And line-level annotations also work:
│ for(uint64_t i = 3; i < num / 2; i+= 2) {
│1 30: movq $0x3,-0x18(%rbp)
0.03 │1 38: mov -0x18(%rbp),%rax
0.03 │ mov -0x10(%rbp),%rcx
│ shr $0x1,%rcx
3.63 │ ┌──cmp %rcx,%rax
│ ├──jae 6f
│ │ if (num % i == 0)
0.03 │ │ mov -0x10(%rbp),%rax
│ │ xor %edx,%edx
89.00 │ │ divq -0x18(%rbp)
│ │ cmp $0x0,%rdx
0.22 │ │↓ jne 5f
│ │ return false;
│ │ movb $0x0,-0x1(%rbp)
│ │↓ jmp 73
│ │ }
3.22 │1 5f:│↓ jmp 61
│ │ for(uint64_t i = 3; i < num / 2; i+= 2) {
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D44892
llvm-svn: 337789
deprecating SymbolResolver and AsynchronousSymbolQuery.
Both lookup overloads take a VSO search order to perform the lookup. The first
overload is non-blocking and takes OnResolved and OnReady callbacks. The second
is blocking, takes a boolean flag to indicate whether to wait until all symbols
are ready, and returns a SymbolMap. Both overloads take a RegisterDependencies
function to register symbol dependencies (if any) on the query.
llvm-svn: 337595
This discards the unresolved symbols set and returns the flags map directly
(rather than mutating it via the first argument).
The unresolved symbols result made it easy to chain lookupFlags calls, but such
chaining should be rare to non-existant (especially now that symbol resolvers
are being deprecated) so the simpler method signature is preferable.
llvm-svn: 337594
A search order is a list of VSOs to be searched linearly to find symbols. Each
VSO now has a search order that will be used when fixing up definitions in that
VSO. Each VSO's search order defaults to just that VSO itself.
This is a first step towards removing symbol resolvers from ORC altogether. In
practice symbol resolvers tended to be used to implement a search order anyway,
sometimes with additional programatic generation of symbols. Now that VSOs
support programmatic generation of definitions via fallback generators, search
orders provide a cleaner way to achieve the desired effect (while removing a lot
of boilerplate).
llvm-svn: 337593
delegate method (and unit test).
The name 'replace' better captures what the old delegate method did: it
returned materialization responsibility for a set of symbols to the VSO.
The new delegate method delegates responsibility for a set of symbols to a new
MaterializationResponsibility instance. This can be used to split responsibility
between multiple threads, or multiple materialization methods.
llvm-svn: 336603
Summary:
CompileOnDemandLayer.cpp uses function in these libraries, and builds
with `-DSHARED_LIB=ON` fail without this.
Reviewers: lhames
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D48995
llvm-svn: 336389
writing them to a buffer and re-loading them.
Also introduces a multithreaded variant of SimpleCompiler
(MultiThreadedSimpleCompiler) for compiling IR concurrently on multiple
threads.
These changes are required to JIT IR on multiple threads correctly.
No test case yet. I will be looking at how to modify LLI / LLJIT to test
multithreaded JIT support soon.
llvm-svn: 336385
The verifier identified several modules that were broken due to incorrect
linkage on declarations. To fix this, CompileOnDemandLayer2::extractFunction
has been updated to change decls to external linkage.
llvm-svn: 336150
LLJIT is a prefabricated ORC based JIT class that is meant to be the go-to
replacement for MCJIT. Unlike OrcMCJITReplacement (which will continue to be
supported) it is not API or bug-for-bug compatible, but targets the same
use cases: Simple, non-lazy compilation and execution of LLVM IR.
LLLazyJIT extends LLJIT with support for function-at-a-time lazy compilation,
similar to what was provided by LLVM's original (now long deprecated) JIT APIs.
This commit also contains some simple utility classes (CtorDtorRunner2,
LocalCXXRuntimeOverrides2, JITTargetMachineBuilder) to support LLJIT and
LLLazyJIT.
Both of these classes are works in progress. Feedback from JIT clients is very
welcome!
llvm-svn: 335670
AsynchronousSymbolQuery::canStillFail checks the value of the callback to
prevent sending it redundant error notifications, so we need to reset it after
running it.
llvm-svn: 335664
CompileOnDemandLayer2 is a replacement for CompileOnDemandLayer built on the ORC
Core APIs. Functions in added modules are extracted and compiled lazily.
CompileOnDemandLayer2 supports multithreaded JIT'd code, and compilation on
multiple threads.
llvm-svn: 334967
materializing weak symbols as strong.
This removes some elaborate flag tweaking and plays nicer with RuntimeDyld,
which relies of weak/common flags to determine whether it should emit a given
weak definition. (Switching to strong up-front makes it appear as if there is
already an overriding definition, which would require an extra back-channel to
override).
llvm-svn: 334966
symbols in debug mode.
The MaterializationResponsibility class hijacks the Materializing flag to track
symbols that have not yet been resolved in order to guard against redundant
resolution. Since this is an API contract check and only enforced in debug mode
there is no reason to maintain the flag state in release mode.
llvm-svn: 334909
Add support for the "@high" and "@higha" symbol modifiers in powerpc64 assembly.
The modifiers represent accessing the segment consiting of bits 16-31 of a
64-bit address/offset.
Differential Revision: https://reviews.llvm.org/D47729
llvm-svn: 334855
Once a symbol has been selected for materialization it can no longer be
overridden. Stripping the weak flag guarantees this (override attempts will
then be treated as duplicate definitions and result in a DuplicateDefinition
error).
llvm-svn: 334771
If WaitUntilReady is set to true then blockingLookup will return once all
requested symbols are ready. If WaitUntilReady is set to false then
blockingLookup will return as soon as all requested symbols have been
resolved. In the latter case, if any error occurs in finalizing the symbols it
will be reported to the ExecutionSession, rather than returned by
blockingLookup.
llvm-svn: 334722
If a VSO has a fallback definition generator attached it will be called during
lookup (and lookupFlags) for any unresolved symbols. The definition generator
can add new definitions to the VSO for any unresolved symbol. This allows VSOs
to generate new definitions on demand.
The immediate use case for this code is supporting VSOs that can import
definitions found via dlsym on demand.
llvm-svn: 334538
