LLVM/clang OpenMP - anyone?

Hi,

has anyone thought about it yet? So far - not even thinking of compiling libomp to wasm - even a minimal example fails in the backend, e.g.:

#pragma optimize off
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include "anet_intrinsic.h"
//#include <omp.h>

int main() {
    #pragma omp parallel num_threads(4)
    {
        #pragma omp critical
        abs(-5555);
    }
}

>>>
C:\LLVM\BUILDLLDB\Debug\bin\clang++ -fopenmp -DDEBUG -mbulk-memory -mmutable-globals -O0 -I.. -I..\.. -I. -Wl,--max-memory=327680 -Wl,--shared-memory -matomics -target wasm32-wasi --sysroot /project/wasi-libc/sysroot-intrin-bulk-memory -Wl,--export-all  -Wl,-L.  -Wl,--entry=__main_void -Wl,--allow-undefined -o omp_dummy.cc.wasm omp_dummy.cc
Common symbols are not yet implemented for Wasm
UNREACHABLE executed at C:\LLVM\llvm\lib\MC\MCWasmStreamer.cpp:164!
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: C:\\LLVM\\BUILDLLDB\\Debug\\bin\\clang++.exe -cc1 -triple wasm32-unknown-wasi -emit-obj -mrelax-all --mrelax-relocations -disable-free -clear-ast-before-backend -main-file-name omp_dummy.cc -mrelocation-model static -mframe-pointer=none -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-cpu generic -target-feature +bulk-memory -target-feature +mutable-globals -target-feature +atomics -fvisibility hidden -debugger-tuning=gdb -fcoverage-compilation-dir=C:\\project\\ALP\\WASM\\exc\\exc_newproposal -resource-dir C:\\LLVM\\BUILDLLDB\\Debug\\lib\\clang\\14.0.0 -D DEBUG -I .. -I ..\\.. -I . -isysroot /project/wasi-libc/sysroot-intrin-bulk-memory -internal-isystem /project/wasi-libc/sysroot-intrin-bulk-memory/include/wasm32-wasi/c++/v1 -internal-isystem /project/wasi-libc/sysroot-intrin-bulk-memory/include/c++/v1 -internal-isystem C:\\LLVM\\BUILDLLDB\\Debug\\lib\\clang\\14.0.0\\include -internal-isystem /project/wasi-libc/sysroot-intrin-bulk-memory/include/wasm32-wasi -internal-isystem /project/wasi-libc/sysroot-intrin-bulk-memory/include -O0 -fdeprecated-macro -fdebug-compilation-dir=C:\\project\\ALP\\WASM\\exc\\exc_newproposal -ferror-limit 19 -fmessage-length=120 -fopenmp -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fcolor-diagnostics -o C:\\Users\\I\\AppData\\Local\\Temp\\omp_dummy-17eebb.o -x c++ omp_dummy.cc
1.      <eof> parser at end of file
2.      Code generation
 #0 0x00007ff7b0397c2c HandleAbort C:\LLVM\llvm\lib\Support\Windows\Signals.inc:408:0
 #1 0x00007ffc24a18e05 (C:\Windows\SYSTEM32\ucrtbased.dll+0xa8e05)
 #2 0x00007ffc24a1ab29 (C:\Windows\SYSTEM32\ucrtbased.dll+0xaab29)
 #3 0x00007ff7b036d21f llvm::llvm_unreachable_internal(char const *, char const *, unsigned int) C:\LLVM\llvm\lib\Support\ErrorHandling.cpp:215:0
 #4 0x00007ff7afca1ed2 llvm::MCWasmStreamer::emitCommonSymbol(class llvm::MCSymbol *, unsigned __int64, unsigned int) C:\LLVM\llvm\lib\MC\MCWasmStreamer.cpp:165:0
 #5 0x00007ff7b207ad3c llvm::AsmPrinter::emitGlobalVariable(class llvm::GlobalVariable const *) C:\LLVM\llvm\lib\CodeGen\AsmPrinter\AsmPrinter.cpp:580:0
 #6 0x00007ff7ada22e9e llvm::WebAssemblyAsmPrinter::emitGlobalVariable(class llvm::GlobalVariable const *) C:\LLVM\llvm\lib\Target\WebAssembly\WebAssemblyAsmPrinter.cpp:177:0
 #7 0x00007ff7b20745b7 llvm::AsmPrinter::doFinalization(class llvm::Module &) C:\LLVM\llvm\lib\CodeGen\AsmPrinter\AsmPrinter.cpp:1737:0
 #8 0x00007ff7af174176 llvm::FPPassManager::doFinalization(class llvm::Module &) C:\LLVM\llvm\lib\IR\LegacyPassManager.cpp:1503:0
 #9 0x00007ff7af175852 `anonymous namespace'::MPPassManager::runOnModule C:\LLVM\llvm\lib\IR\LegacyPassManager.cpp:1590:0
#10 0x00007ff7af176375 llvm::legacy::PassManagerImpl::run(class llvm::Module &) C:\LLVM\llvm\lib\IR\LegacyPassManager.cpp:542:0
#11 0x00007ff7af16e292 llvm::legacy::PassManager::run(class llvm::Module &) C:\LLVM\llvm\lib\IR\LegacyPassManager.cpp:1682:0
#12 0x00007ff7b0cf0d01 `anonymous namespace'::EmitAssemblyHelper::RunCodegenPipeline C:\LLVM\clang\lib\CodeGen\BackendUtil.cpp:1520:0
#13 0x00007ff7b0cf1f38 `anonymous namespace'::EmitAssemblyHelper::EmitAssembly C:\LLVM\clang\lib\CodeGen\BackendUtil.cpp:1550:0
#14 0x00007ff7b0cece03 clang::EmitBackendOutput(class clang::DiagnosticsEngine &, class clang::HeaderSearchOptions const &, class clang::CodeGenOptions const &, class clang::TargetOptions const &, class clang::LangOptions const &, class llvm::StringRef, class llvm::Module *, enum clang::BackendAction, class std::unique_ptr<class llvm::raw_pwrite_stream, struct std::default_delete<class llvm::raw_pwrite_stream>>) C:\LLVM\clang\lib\CodeGen\BackendUtil.cpp:1714:0
#15 0x00007ff7b7aeead1 clang::BackendConsumer::HandleTranslationUnit(class clang::ASTContext &) C:\LLVM\clang\lib\CodeGen\CodeGenAction.cpp:374:0
#16 0x00007ff7b4b5f538 clang::ParseAST(class clang::Sema &, bool, bool) C:\LLVM\clang\lib\Parse\ParseAST.cpp:178:0
#17 0x00007ff7b1976a07 clang::ASTFrontendAction::ExecuteAction(void) C:\LLVM\clang\lib\Frontend\FrontendAction.cpp:1076:0
#18 0x00007ff7b7ae24e7 clang::CodeGenAction::ExecuteAction(void) C:\LLVM\clang\lib\CodeGen\CodeGenAction.cpp:1108:0
#19 0x00007ff7b19763be clang::FrontendAction::Execute(void) C:\LLVM\clang\lib\Frontend\FrontendAction.cpp:971:0
#20 0x00007ff7b18f5106 clang::CompilerInstance::ExecuteAction(class clang::FrontendAction &) C:\LLVM\clang\lib\Frontend\CompilerInstance.cpp:1030:0
#21 0x00007ff7b1b62648 clang::ExecuteCompilerInvocation(class clang::CompilerInstance *) C:\LLVM\clang\lib\FrontendTool\ExecuteCompilerInvocation.cpp:261:0
#22 0x00007ff7ab8becf4 cc1_main(class llvm::ArrayRef<char const *>, char const *, void *) C:\LLVM\clang\tools\driver\cc1_main.cpp:246:0
#23 0x00007ff7ab8aa410 ExecuteCC1Tool C:\LLVM\clang\tools\driver\driver.cpp:317:0

Can anyone oversee what must be implemented to achieve this?

Thanks,
S.

Reproduce the minimal OpenMP example with the shown clang++ wasm32-wasi command. Start at llvm/lib/MC/MCWasmStreamer.cpp:164 and the WebAssemblyAsmPrinter.cpp:177 call path in the stack trace. Done means the example no longer aborts in the backend and the required OpenMP support is clearly identified.