[cfe-dev] JIT doens't resolve address
Lang Hames via cfe-dev
cfe-dev at lists.llvm.org
Mon May 1 11:04:03 PDT 2017
Hi Björn,
Does the module containing your main function have a triple or data layout?
There should be a couple of lines at the top of the module that look like:
target data layout = "..."
target triple = "..."
If these lines are missing (especially the data layout) then the problem
might be name mangling: findSymbol is applying the default system specific
mangling (which on Windows may include prefixes), but the module is being
compiled without mangling.
Can you share the header for your module?
Could you also modify your JIT to print DL.getStringRepresentation() in the
constructor and share this?
These should match.
Cheers,
Lang.
On Fri, Apr 21, 2017 at 12:50 PM, Will Dietz <willdtz at gmail.com> wrote:
> Hmm, I tried using your code (copy+pasted and then mass-dumped headers to
> fix includes), and it seems to work fine for me:
>
> https://gist.github.com/dtzWill/df84b64a73001532e3fcfe73a2cffb
> b9#file-test-log
>
> Do you get different results when using your LLVM? If not, can you
> identify the differences between your code and what I constructed from your
> snippets?
>
> I noticed "PAUSE", are you on Windows? I'm not sure what the
> functionality/status of the JIT on Windows is, perhaps someone else can
> comment on that.
>
> ~Will
>
> On Fri, Apr 21, 2017 at 1:03 AM, via cfe-dev <cfe-dev at lists.llvm.org>
> wrote:
>
>> Hello Lang,
>>
>> the Code for my jit_main is a normal printf-HelloWorld program. I opended
>> the file with notepad and found the following:
>>
>> ; Function Attrs: noinline norecurse uwtable
>> define i32 @main() #0 {
>> entry:
>> %retval = alloca i32, align 4
>> store i32 0, i32* %retval, align 4
>> %call = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([35 x
>> i8], [35 x i8]* @"\01??_C at _0CD@CMJEAMCD at Plansc
>> hbeckilein?5sagt?5Halloilein@", i32 0, i32 0))
>> %call1 = call i32 @system(i8* getelementptr inbounds ([6 x i8], [6 x
>> i8]* @"\01??_C at _05DIAHPDGL@PAUSE?$AA@", i32 0, i32 0))
>> ret i32 0
>> }
>>
>> So... there is a main... Anyway! The code for the main is this one:
>> #include <stdio.h>
>> #include <stdlib.h>
>>
>> int main()
>> {
>> printf("Planschbeckilein sagt Halloilein!\n");
>> system("PAUSE");
>>
>> return 0;
>> }
>>
>> Kind regards
>> Björn
>>
>>
>>
>> From: Lang Hames <lhames at gmail.com>
>> To: bjoern.gaier at horiba.com
>> Cc: Clang Dev <cfe-dev at lists.llvm.org>
>> Date: 20.04.2017 22:54
>> Subject: Re: [cfe-dev] JIT doens't resolve address
>> ------------------------------
>>
>>
>>
>> Hi Bjoern,
>>
>> Sorry - I just noticed that the address for your "main" function has come
>> back as '0'. In this case the answer is even simpler: The JIT never found
>> the function at all, and so definitely didn't have any external symbols to
>> resolve, so it never called the resolver.
>>
>> A failure to find main has three likely causes:
>>
>> (1) jit_main.ll does not define main,
>> (2) jit_main.ll defines main with private/internal linkage (the JIT can't
>> see private/internal symbols in general)
>> (3) jit_main.ll defines main with external linkage, but a system mangling
>> is applied (e.g. on MacOSX 'main' is mangled to '_main'). The mangler code
>> in your findSymbol function *should* correct for this, but this may fail if
>> the default data layout for your TargetMachine varies from the Module's
>> DataLayout.
>>
>> Can you share the contents of your jit_main.ll Module?
>>
>> Cheers,
>> Lang.
>>
>>
>> On Thu, Apr 20, 2017 at 1:35 PM, Lang Hames <*lhames at gmail.com*
>> <lhames at gmail.com>> wrote:
>> HI Bjoern,
>>
>> There are two kinds of symbol lookup in the JIT:
>>
>> (1) You want to find a symbol defined JIT'd code. This is what
>> "findSymbol" on the JIT class does.
>>
>> (2) The JIT wants to fix up a module that contains references to symbols
>> defined elsewhere (either in your program, or in other JIT'd code). This is
>> the SymbolResolver's job.
>>
>> So assuming your main function in main.ll is trivial, e.g.
>>
>> int main() {
>> return 0;
>> }
>>
>> then your findSymbol call will return the address of the JIT'd main
>> without ever needing to look anything up in the resolver.
>>
>> If, on the other hand, your main function contains an external reference,
>> e.g.
>>
>> int main() {
>> printf("Hello, World!"); // Reference to externally defined function
>> printf.
>> return 0;
>> }
>>
>> Then you'll receive a call back on your resolver looking for the address
>> of printf.
>>
>> Hope this helps!
>>
>> Cheers,
>> Lang.
>>
>> On Thu, Apr 20, 2017 at 6:43 AM, via cfe-dev <*cfe-dev at lists.llvm.org*
>> <cfe-dev at lists.llvm.org>> wrote:
>> Hello LLVM-World,
>>
>> I was following the "Building a JIT in LLVM"-Tutorial and tried to load a
>> normal main. My code is the following:
>> class Jitter
>> {
>> private:
>> std::unique_ptr<TargetMachine> TM;
>> const DataLayout DL;
>> ObjectLinkingLayer<> ObjectLayer;
>> IRCompileLayer<decltype(ObjectLayer)> CompileLayer;
>>
>> public:
>> typedef decltype(CompileLayer)::ModuleSetHandleT ModuleHandle;
>>
>> Jitter() : TM(EngineBuilder().selectTarget()), DL(TM->
>> createDataLayout()),
>> CompileLayer(ObjectLayer, SimpleCompiler(*TM))
>> {printf("!");
>> llvm::sys::DynamicLibrary::LoadLibraryPermanently(nullptr);
>> }
>>
>> TargetMachine &getTargetMachine() { return *TM; }
>>
>> ModuleHandle addModule(std::unique_ptr<Module> &&M) {
>> // Build our symbol resolver:
>> // Lambda 1: Look back into the JIT itself to find symbols that are
>> part of
>> // the same "logical dylib".
>> // Lambda 2: Search for external symbols in the host process.
>> auto Resolver = createLambdaResolver(
>> [&](const std::string &Name)
>> {
>> printf("FLUSH :0\n");
>>
>> if (auto Sym = CompileLayer.findSymbol(Name, false))
>> return Sym;
>> return JITSymbol(nullptr);
>> },
>> [](const std::string &S)
>> {
>> printf("PLUSH :0\n");
>>
>> if (auto SymAddr =
>> RTDyldMemoryManager::getSymbolAddressInProcess(S))
>> return JITSymbol(SymAddr, JITSymbolFlags::Exported);
>> return JITSymbol(nullptr);
>> });
>>
>> // Build a singleton module set to hold our module.
>> std::vector<std::unique_ptr<Module>> Ms;
>> Ms.push_back(std::move(M));
>>
>> // Add the set to the JIT with the resolver we created above and a
>> newly
>> // created SectionMemoryManager.
>> return CompileLayer.addModuleSet(std::move(Ms),
>> make_unique<SectionMemoryManager>(),
>> std::move(Resolver));
>> }
>>
>> JITSymbol findSymbol(const std::string Name) {
>> std::string MangledName;
>> raw_string_ostream MangledNameStream(MangledName);
>> Mangler::getNameWithPrefix(MangledNameStream, Name, DL);
>> printf("Tzearch for: %s\n\n", MangledNameStream.str());
>> return CompileLayer.findSymbol(MangledNameStream.str(), false);
>> }
>>
>> void removeModule(ModuleHandle H) {
>> CompileLayer.removeModuleSet(H);
>> }
>>
>> };
>>
>>
>> And calling from main with:
>> int main()
>> {
>> llvm::InitializeNativeTarget();
>> llvm::InitializeNativeTargetAsmPrinter();
>> llvm::InitializeNativeTargetAsmParser();
>>
>> llvm::LLVMContext context;
>> llvm::SMDiagnostic dia;
>>
>> std::unique_ptr<llvm::Module> M = llvm::parseIRFile("./jit_main.
>> ll", dia, context);
>> Jitter jit;
>> printf("Wuff?");
>> Jitter::ModuleHandle h = jit.addModule(std::move(M));
>> printf("KNUFF!\n");
>>
>> printf("Kuchen! 0x%p\n", jit.findSymbol("main").getAddress());
>>
>> system("PAUSE");
>> return 0;
>> }
>>
>> The Code runs without a fail, but when the programm tries to resolve
>> "main" the address is 0. The strange thing: the printf "FLUSH :0\n" and "PLUSH
>> :0\n" are never called, so did the code never compiled? What I'm doing
>> wrong?
>>
>> Kind regards
>> Björn
>> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
>> USt.ID-Nr. DE 114 165 789
>> Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode,
>> Heiko Lampert, Takashi Nagano, Takeshi Fukushima.
>> _______________________________________________
>> cfe-dev mailing list
>> *cfe-dev at lists.llvm.org* <cfe-dev at lists.llvm.org>
>> *http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev*
>> <http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev>
>>
>>
>>
>>
>>
>> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
>> USt.ID-Nr. DE 114 165 789
>> Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode,
>> Heiko Lampert, Takashi Nagano, Takeshi Fukushima.
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20170501/2ca10939/attachment.html>
More information about the cfe-dev
mailing list