[llvm-dev] LLVM Orc Weekly #28 -- ORC Runtime Prototype update

Stefan Gränitz via llvm-dev
Fri, 22 Jan 2021 10:53:12 -0000

I am always in favor of getting JIT improvements into mainline as soon
as possible. Also, simplifying APIs is an important goal.

On the other hand this raises a few general questions for me:

IIUC the current patch introduces a dependency from LLVM to
compiler-rt/clang build artifacts, because the llvm-jitlink-executor
executable is fully functional only if it can find the clang_rt.orc
static library in the build tree. Do we have dependencies like that in
mainline so far?

And how does it affect testing? So far, it seems we have no testing for
out-of-process execution, because the only tool that exercises this
functionality is llvm-jitlink, which itself is mostly used as a testing
helper. If the functionality now moves into the TargetProcess library,
it might be worth thinking through the test strategy first.

At the moment, the TargetProcess library is only used by JITLink. Will
it stay like that? If so, RuntimeDyld-based JITs will not be affected by
the patch. Will it be possible to build and run e.g. a LLJIT instance
with a RuntimeDyldLinkingLayer if only LLVM gets built (omitting
LLVM_ENABLE_PROJECTS="clang;compiler-rt")?

Last but not least, there are examples that use JITLink. Could we still
build and run them if only LLVM gets built?

Thanks,
Stefan

On 19/01/2021 23:08, Lang Hames wrote:
> Big question for JIT clients: Does anyone have any objection to APIs
> in ORC *relying* on the runtime being loaded in the target? If so, now
> is the time to let me know. :)
>
> I think possible objections are JIT'd program startup time (unlikely
> to be very high, and likely fixable via careful runtime design and
> pre-linking of parts of the runtime), and difficulties building
> compiler-rt (which sounds like something we should fix in compiler-rt).
>
> If we can assume that the runtime is loadable then we can
> significantly simplify the TargetProcess library, and
> TargetProcessControl API, and further accelerate feature development
> in LLVM 13.
>
> -- Lang.
>
> On Tue, Jan 19, 2021 at 8:45 AM Lang Hames <lhames at gmail.com
> <mailto:lhames at gmail.com>> wrote:
>
>     Hi Stefan,
>
>         % ./bin/llvm-jitlink -oop-executor inits.o
>         JIT session error: Symbols not found: [
>         __ZTIN4llvm6detail14format_adapterE ]
>
>
>     I've been testing with a debug build:
>
>     % xcrun cmake -GNinja -DCMAKE_BUILD_TYPE=Debug
>     -DLLVM_ENABLE_PROJECTS="llvm;clang;compiler-rt" ../llvm
>
>     Matching this build might fix the issue, though building with my
>     config (if it works) is only a short-term fix. The error that
>     you're seeing implies that the runtime is dependending on a symbol
>     from libSupport that is not being linked in to the target
>     (llvm-jitlink-executor). I'll aim to break these dependencies on
>     libSupport in the future. Mostly that means either removing the
>     dependence on llvm::Error / llvm::Expected (e.g. by creating
>     stripped down versions for the orc runtime), or making those types
>     header-only.
>
>     -- Lang.
>
>
>
>
>
>     On Tue, Jan 19, 2021 at 12:50 AM Stefan Gränitz
>     <stefan.graenitz at gmail.com <mailto:stefan.graenitz at
gmail.com>> wrote:
>
>         Wow, thanks for the update. One more ORC milestone in a short
>         period of time!
>
>         On macOS I built the C++ example like this:
>
>         % cmake -GNinja -DLLVM_TARGETS_TO_BUILD=host
>         -DLLVM_ENABLE_PROJECTS="clang;compiler-rt" ../llvm
>         % ninja llvm-jitlink llvm-jitlink-executor
>         lib/clang/12.0.0/lib/darwin/libclang_rt.orc_osx.a
>         % clang++ -c -o inits.o inits.cpp
>
>         The in-process version works perfectly, but with the
>         out-of-process flag the examples fails:
>
>         % ./bin/llvm-jitlink inits.o
>         Foo::Foo()
>         Foo::foo()
>         Foo::~Foo()
>         % ./bin/llvm-jitlink -oop-executor inits.o
>         JIT session error: Symbols not found: [
>         __ZTIN4llvm6detail14format_adapterE ]
>
>         Any idea what could go wrong here? Otherwise I can try to
>         debug it later this week. (Full error below.)
>
>         Best
>         Stefan
>
>         --
>
>         JIT session error: Symbols not found: [
>         __ZTIN4llvm6detail14format_adapterE ]
>
/Users/staefsn/Develop/LLVM/monorepo/llvm-orc-runtime/build/bin/llvm-jitlink:
>         Failed to materialize symbols: { (Main, {
>         ___orc_rt_macho_symbol_lookup_remote,
>
__ZN4llvm3orc6shared21WrapperFunctionResult22destroyWithArrayDeleteE39LLVMOrcSharedCWrapperFunctionResultDatay,
>
__ZNSt3__113__vector_baseIN4llvm3orc6shared25MachOJITDylibInitializersENS_9allocatorIS4_EEED2Ev,
>
__ZNK4llvm8ExpectedINS_3orc6shared21WrapperFunctionResultEE22fatalUncheckedExpectedEv,
>
__ZN4llvm3orc6shared21toWrapperFunctionBlobIJNSt3__112basic_stringIcNS3_11char_traitsIcEENS3_9allocatorIcEEEEEEENS1_21WrapperFunctionResultEDpRKT_,
>         __ZN4llvm3orc6shared20VectorRawByteChannelD1Ev,
>
__ZN4llvm3orc6shared21SequenceSerializationINS1_20VectorRawByteChannelEJNSt3__16vectorINS1_25MachOJITDylibInitializers13SectionExtentENS4_9allocatorIS7_EEEESA_SA_EE11deserializeISA_JSA_SA_EEENS_5ErrorERS3_RT_DpRT0_,
>
__ZNSt3__16vectorIN4llvm3orc6shared25MachOJITDylibInitializers13SectionExtentENS_9allocatorIS5_EEE8__appendEm,
>
__ZN4llvm3orc6shared21toWrapperFunctionBlobIJyNSt3__112basic_stringIcNS3_11char_traitsIcEENS3_9allocatorIcEEEEEEENS1_21WrapperFunctionResultEDpRKT_,
>         __ZN4llvm29VerifyEnableABIBreakingChecksE,
>
__ZN4llvm15format_providerImvE6formatERKmRNS_11raw_ostreamENS_9StringRefE,
>
__ZNSt3__114__split_bufferIN4llvm3orc6shared25MachOJITDylibInitializersERNS_9allocatorIS4_EEED2Ev,
>         __ZTVN4llvm6detail23provider_format_adapterIRmEE,
>
__ZN4llvm3orc6shared21SequenceSerializationINS1_20VectorRawByteChannelEJyNSt3__112basic_stringIcNS4_11char_traitsIcEENS4_9allocatorIcEEEEEE9serializeIRKyJRKSA_EEENS_5ErrorERS3_OT_DpOT0_,
>         __ZTVN4llvm6detail23provider_format_adapterImEE,
>
__ZN4llvm6detail23provider_format_adapterImE6formatERNS_11raw_ostreamENS_9StringRefE,
>         __ZN4llvm6detail23provider_format_adapterIRmED1Ev,
>         ___orc_rt_macho_get_deinitializers_tag,
>         __ZN4llvm6detail23provider_format_adapterIRmED0Ev,
>         __ZTVN4llvm3orc6shared14RawByteChannelE,
>         __ZN6orc_rt12jit_dispatchEPKvN4llvm8ArrayRefIhEE,
>         __ZN4llvm3orc6shared20VectorRawByteChannelD0Ev,
>         __ZTVN4llvm3orc6shared20VectorRawByteChannelE,
>         __ZN4llvm8cantFailENS_5ErrorEPKc,
>         __ZN4llvm6detail23provider_format_adapterImED1Ev,
>         __ZTVN4llvm6detail23provider_format_adapterIRjEE,
>         __ZN4llvm6detail23provider_format_adapterImED0Ev,
>
__ZN4llvm15format_providerIjvE6formatERKjRNS_11raw_ostreamENS_9StringRefE,
>         __ZTSN4llvm3orc6shared14RawByteChannelE,
>
__ZN4llvm6detail23provider_format_adapterIRjE6formatERNS_11raw_ostreamENS_9StringRefE,
>         __ZN4llvm6detail23provider_format_adapterIRjED0Ev,
>
__ZN4llvm3orc6shared19SerializationTraitsINS1_20VectorRawByteChannelENSt3__16vectorINS1_25MachOJITDylibInitializersENS4_9allocatorIS6_EEEES9_vE11deserializeERS3_RS9_,
>         __ZTIN4llvm6detail23provider_format_adapterImEE,
>
__ZN4llvm6detail15HelperFunctions15consumeHexStyleERNS_9StringRefERNS_13HexPrintStyleE,
>         __ZTIN4llvm6detail23provider_format_adapterIRmEE,
>         ___orc_rt_macho_get_initializers_tag,
>         __ZTSN4llvm6detail23provider_format_adapterImEE,
>         __ZN4llvm3orc6shared20VectorRawByteChannel4sendEv,
>
__ZN4llvm6detail23provider_format_adapterIRmE6formatERNS_11raw_ostreamENS_9StringRefE,
>         ___orc_rt_macho_symbol_lookup_tag,
>         __ZTSN4llvm6detail23provider_format_adapterIRmEE,
>         __ZN4llvm3orc6shared20VectorRawByteChannel11appendBytesEPKcj,
>         __ZTSN4llvm6detail23provider_format_adapterIRjEE,
>         __ZN4llvm3orc6shared20VectorRawByteChannel9readBytesEPcj,
>         __ZTSN4llvm3orc6shared20VectorRawByteChannelE,
>         __ZN4llvm6detail23provider_format_adapterIRjED1Ev,
>         __ZN4llvm3orc6shared14RawByteChannelD1Ev,
>
__ZN4llvm3orc6shared23fromWrapperFunctionBlobIJNSt3__16vectorINS1_25MachOJITDylibInitializersENS3_9allocatorIS5_EEEEEEENS_5ErrorENS_8ArrayRefIhEEDpRT_,
>         __ZN4llvm3orc6shared14RawByteChannelD0Ev,
>
__ZN4llvm3orc6shared21SequenceSerializationINS1_20VectorRawByteChannelEJyyNSt3__16vectorINS1_25MachOJITDylibInitializers13SectionExtentENS4_9allocatorIS7_EEEESA_SA_EE11deserializeIyJySA_SA_SA_EEENS_5ErrorERS3_RT_DpRT0_,
>
__ZNSt3__16vectorIN4llvm3orc6shared25MachOJITDylibInitializersENS_9allocatorIS4_EEE8__appendEm,
>
__ZN4llvm3orc6shared21SequenceSerializationINS1_20VectorRawByteChannelEJyyEE11deserializeIyJyEEENS_5ErrorERS3_RT_DpRT0_,
>
__ZNSt3__16vectorIN4llvm3orc6shared25MachOJITDylibInitializersENS_9allocatorIS4_EEE6resizeEm,
>
__ZN4llvm3orc6shared19SerializationTraitsINS1_20VectorRawByteChannelENSt3__112basic_stringIcNS4_11char_traitsIcEENS4_9allocatorIcEEEESA_vE11deserializeERNS1_14RawByteChannelERSA_,
>
__ZN4llvm3orc6shared23fromWrapperFunctionBlobIJyEEENS_5ErrorENS_8ArrayRefIhEEDpRT_,
>         __ZTIN4llvm6detail23provider_format_adapterIRjEE,
>
__ZN4llvm3orc6shared21WrapperFunctionResult20getAnyOutOfBandErrorEv,
>         __ZTIN4llvm3orc6shared20VectorRawByteChannelE,
>         ___orc_rt_macho_get_initializers_remote,
>         __ZTIN4llvm3orc6shared14RawByteChannelE,
>
__ZNSt3__16vectorIhNS_9allocatorIhEEE26__swap_out_circular_bufferERNS_14__split_bufferIhRS2_EE,
>
__ZN4llvm3orc6shared19SerializationTraitsINS1_20VectorRawByteChannelENSt3__16vectorINS1_25MachOJITDylibInitializers13SectionExtentENS4_9allocatorIS7_EEEESA_vE11deserializeERS3_RSA_
>         }) }
>
/Users/staefsn/Develop/LLVM/monorepo/llvm-orc-runtime/build/bin/llvm-jitlink-executor:Response
>         has unknown sequence number 527162
>
>         On 18/01/2021 08:55, Lang Hames wrote:
>>         Hi All,
>>
>>         Happy 2021!
>>
>>         I've just posted a new Orc Runtime Preview patch:
>>
https://github.com/lhames/llvm-project/commit/8833a7f24693f1c7a3616438718e7927c6624894
>>
<https://github.com/lhames/llvm-project/commit/8833a7f24693f1c7a3616438718e7927c6624894>
>>
>>         Quick background:
>>
>>         To date, neither ORC nor MCJIT have had their own runtime
>>         libraries. This has limited and complicated the
>>         implementation of many features (e.g. jit re-entry functions,
>>         exception handling, JID'd initializers and
de-initializers),
>>         and more-or-less prevented the implementation of others (e.g.
>>         native thread local storage).
>>
>>         Late last year I started work on a prototype ORC runtime
>>         library to address this, and with the above commit I've
>>         finally got something worth sharing.
>>
>>         The prototype above is simultaneously limited and complex.
>>         Limited, in that it only tackles a small subset of the
>>         desired functionality. Complex in that it's one of the most
>>         involved pieces of functionality that I anticipate
>>         supporting, as it requires two-way communication between the
>>         executor and JIT processes. My aim in choosing to tackle the
>>         hard part first was to get a sense of our ultimate
>>         requirements for the project, particularly in regards to
>>         /where it should live within the LLVM Project/. It's not a
>>         perfect fit for LLVM proper: there will be lots of target
>>         specific code, including assembly, and it should be easily
>>         buildable for multiple targets (that sounds more like
>>         compiler-rt). On the other hand it's not a perfect fit for
>>         compiler-rt: it shares data structures with LLVM, and it
>>         would be very useful to be able to re-use llvm::Error  /
>>         llvm::Expected (that sounds like LLVM). At the moment I think
>>         the best way to square things would be to keep it in
>>         compiler-rt, allow inclusion of header-only code from LLVM in
>>         compiler-rt, and then make Error / Expected header-only (or
>>         copy / adapt them for this library). This will be a
>>         discussion for llvm-dev at some point in the near future.
>>
>>         On to the actual functionality though: The prototype makes
>>         significant changes to the MachOPlatform class and introduces
>>         an ORC runtime library in compiler-rt/lib/orc. Together,
>>         these changes allow us to emulate the dlopen / dlsym /
>>         dlclose in the JIT executor process. We can use this to
>>         define what it means to run a /JIT program/, rather than just
>>         running a JIT function (the way
>>         TargetProcessControl::runAsMain does):
>>
>>
ORC_RT_INTERFACE int64_t __orc_rt_macho_run_program(int argc, char *argv[])
>>         {
>>           using MainTy = int (*)(int, char *[]);
>>
>>           void *H = __orc_rt_macho_jit_dlopen("Main",
ORC_RT_RTLD_LAZY);
>>           if (!H) {
>>             __orc_rt_log_error(__orc_rt_macho_jit_dlerror());
>>             return -1;
>>           }
>>
>>
  auto *Main = reinterpret_cast<MainTy>(__orc_rt_macho_jit_dlsym(H, "main"));
>>           if (!Main) {
>>             __orc_rt_log_error(__orc_rt_macho_jit_dlerror());
>>             return -1;
>>           }
>>
>>           int Result = Main(argc, argv);
>>
>>           if (__orc_rt_macho_jit_dlclose(H) == -1)
>>             __orc_rt_log_error(__orc_rt_macho_jit_dlerror());
>>
>>           return Result;
>>         }
>>
>>         The
>>         functions __orc_rt_macho_jit_dlopen, __orc_rt_macho_jit_dlsym,
>>         and __orc_rt_macho_jit_dlclose behave the same as their
>>         dlfcn.h counterparts (dlopen, dlsym, dlclose), but operate on
>>         JITDylibs rather than regular dylibs. This includes running
>>         static initializers and registering with language runtimes
>>         (e.g. ObjC).
>>
>>         While we could run static initializers before (e.g. via
>>         LLJIT::runConstructors), we had to initiate this from the JIT
>>         process side, which has two significant drawbacks: (1) Extra
>>         RPC round trips, and (2) in the out-of-process case:
>>         initializers not running on the executor thread that
>>         requested them, since that thread will be blocked waiting for
>>         its call to return. Issue (1) only affects performance, but
>>         (2) can affect correctness if the initializers modify thread
>>         local values, or interact with locks or threads. Interacting
>>         with threads from initializers is generally best avoided, but
>>         nonetheless is done by real-world code, so we want to support
>>         it. By using the runtime we can improve both performance and
>>         correctness (or at least consistency with current behavior).
>>
>>         The effect of this is that we can now load C++, Objective-C
>>         and Swift programs in the JIT and expect them to run
>>         correctly, at least for simple cases. This works regardless
>>         of whether the JIT'd code runs in-process or
out-of-process.
>>         To test all this I have integrated support for the prototype
>>         runtime into llvm-jitlink. You can demo output from this tool
>>         below for two simple input programs: One swift, one C++. All
>>         of this is MachO specific at the moment, but provides a
>>         template that could be easily re-used to support this on ELF
>>         platforms, and likely on COFF platforms too.
>>
>>         While the discussion on where the runtime should live plays
>>         out I will continue adding / moving functionality to the
>>         prototype runtime. Next up will be eh-frame registration and
>>         resolver functions (both currently in OrcTargetProcess).
>>         After that I'll try to tackle support for native MachO
thread
>>         local storage.
>>
>>         As always: Questions and comments are very welcome.
>>
>>         -- Lang.
>>
>>         lhames at Langs-MacBook-Pro scratch % cat foo.swift
>>         class MyClass {
>>           func foo() {
>>             print("foo")
>>           }
>>         }
>>
>>         let m = MyClass()
>>         m.foo();
>>
>>         lhames at Langs-MacBook-Pro scratch % xcrun swiftc -emit-object
>>         -o foo.o foo.swift
>>         lhames at Langs-MacBook-Pro scratch % llvm-jitlink -dlopen
>>         /usr/lib/swift/libswiftCore.dylib foo.o
>>         foo
>>         lhames at Langs-MacBook-Pro scratch % llvm-jitlink
-oop-executor
>>         -dlopen /usr/lib/swift/libswiftCore.dylib foo.o
>>         foo
>>         lhames at Langs-MacBook-Pro scratch % cat inits.cpp
>>         #include <iostream>
>>
>>         class Foo {
>>         public:
>>           Foo() { std::cout << "Foo::Foo()\n"; }
>>           ~Foo() { std::cout << "Foo::~Foo()\n"; }
>>           void foo() { std::cout << "Foo::foo()\n"; }
>>         };
>>
>>         Foo F;
>>
>>         int main(int argc, char *argv[]) {
>>           F.foo();
>>           return 0;
>>         }
>>         lhames at Langs-MacBook-Pro scratch % xcrun clang++ -c -o
>>         inits.o inits.cpp
>>         lhames at Langs-MacBook-Pro scratch % llvm-jitlink inits.o

>>
>>         Foo::Foo()
>>         Foo::foo()
>>         Foo::~Foo()
>>         lhames at Langs-MacBook-Pro scratch % llvm-jitlink
-oop-executor
>>         inits.o
>>         Foo::Foo()
>>         Foo::foo()
>>         Foo::~Foo()
>
>         --
>         https://flowcrypt.com/pub/stefan.graenitz at gmail.com
<https://flowcrypt.com/pub/stefan.graenitz at gmail.com>
>
--
https://flowcrypt.com/pub/stefan.graenitz at gmail.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20210122/a8da545d/attachment-0001.html>