Supporting xsimd through xeus-cpp-lite

[anutosh491]

Hey @serge-sans-paille

At this point, xeus-cpp-lite is able to support quite some header only libraries. For eg (nlohmann/json, boost-cpp etc)

And at this point we should also be able to support xsimd (we are able to do SIMD smoothly here)

[anutosh491]

But with xsimd we get some errors !

This point to a failed assertion here (https://github.com/llvm/llvm-project/blob/main/clang/lib/Interpreter/Interpreter.cpp#L453) and suggests that we rebuild with assertions
Uncaught (in promise) RuntimeError: Aborted(Assertion failed: T.TheModule, at: /home/runner/work/recipes/recipes/output/bld/rattler-build_llvm_1737094283/work/clang/lib/Interpreter/Interpreter.cpp,453,Execute). Build with -sASSERTIONS for more info.

On Doing that, I see the following

Which is a RuntimeError: memory access out of bounds error.

[anutosh491]

So not sure what the error is as of now

1. Maybe in llvm
2. Maybe some flag or something missing while building xeus-cpp-lite (most flags come out of here and are defined here for us to look into)

But here are the build instructions for the replicate the above

1. Currently xeus-cpp-lite doesn't have functionality to access the resource-dir headers where wasm_simd128.h lies (we can currently make use of the standard headers from emscripten's sysroot though and resource dir would be supported soon)

2. So in the build instructions for building xeus-cpp-lite (https://github.com/compiler-research/xeus-cpp?tab=readme-ov-file#installation-within-a-mamba-environment-wasm-build-instructions)

Just copy the contents from emsdk/upstream/lib/clang/18/include/wasm_simd128.h to emsdk/upstream/emscripten/cache/sysroot/include/wasm_simd128.h

before the emcmake cmake ... step

3. Add xsimd (recipe hosted on emscripten-forge) to your PREFIX)
   P.S : There might be something wrong with how xsimd is built too ... so we might need to check that too.

4. Then simply follow the build instructions and we should be able to access xsimd headers through xeus-cpp-lite !

Overall I think we have all tools necessary to run xsimd with xeus-cpp-lite but something is being missed here.

[serge-sans-paille]

Hey @anutosh491 Indeed based on the scenario you provide, everything should be working. I'll definitively have a look!

[anutosh491]

Thanks Serge for the reply

1. Doesn't look like an obvious llvm (clang-repl) error to me as we're able to load other libraries smoothly !
2. I don't see an obvious reason for a "memory out of bounds error" and hence I am thinking its either some flag or the way we frame our recipe that might be not working as expected (https://github.com/emscripten-forge/recipes/tree/main/recipes/recipes_emscripten/xsimd)

[anutosh491]

We now moved to a later version of emsdk. Everything was shifted from 3.1.45 to 3.1.73 !

[anutosh491]

I was trying it with my toy project and using llvm built with assertions

I see this

Need to see if this is exactly what's going wrong !

Here is the error message though

In file included from <<< inputs >>>:1:
In file included from input_line_2:1:
In file included from /include/xsimd/xsimd.hpp:62:
In file included from /include/xsimd/types/xsimd_batch.hpp:492:
In file included from /include/xsimd/types/../arch/xsimd_isa.hpp:124:
/include/xsimd/types/../arch/./xsimd_wasm.hpp:1339:20: error: always_inline function 'wasm_f64x2_make' requires target feature 'simd128', but would be inlined into function 'set' that is compiled without support for 'simd128'
 1339 |             return wasm_f64x2_make(values...);

[serge-sans-paille]

This looks like your whole project should be compiled with simd128 activated, maybeincluding xeus-lite-cpp itself?

[anutosh491]

Hey Serge,

Yeah I was thinking the same.

Even before we go to xeus-cpp-lite, I am trying to get stuff working with a smaller toy project (as involves lesser things and makes debugging easier)

So I see just 3 factors here

1. xsimd
2. llvm (clang & lld) - We only depend on libclangInterpreter.a as such that we need to link against the final target. Currently being built using

emcmake cmake -DCMAKE_BUILD_TYPE=MinSizeRel         \
    -DCMAKE_PREFIX_PATH=$PREFIX                     \
    -DLLVM_HOST_TRIPLE=wasm32-unknown-emscripten    \
    -DLLVM_TARGETS_TO_BUILD="WebAssembly"           \
    -DLLVM_ENABLE_ASSERTIONS=ON                     \
    -DLLVM_INCLUDE_BENCHMARKS=OFF                   \
    -DLLVM_INCLUDE_EXAMPLES=OFF                     \
    -DLLVM_INCLUDE_TESTS=OFF                        \
    -DLLVM_ENABLE_LIBEDIT=OFF                       \
    -DLLVM_ENABLE_PROJECTS="clang;lld"              \
    -DCMAKE_VERBOSE_MAKEFILE=ON                     \
    -DLLVM_ENABLE_THREADS=OFF                       \
    -DLLVM_ENABLE_ZSTD=OFF                          \
    -DLLVM_ENABLE_LIBXML2=OFF                       \
    -DCLANG_ENABLE_STATIC_ANALYZER=OFF              \
    -DCLANG_ENABLE_ARCMT=OFF                        \
    -DCLANG_ENABLE_BOOTSTRAP=OFF                    \
    -DCMAKE_CXX_FLAGS="-Dwait4=__syscall_wait4 -fexceptions" \
    ../llvm

3. clang-repl-wasm which is the toy project ... that uses the following

find_package(LLVM REQUIRED CONFIG)
find_package(LLD REQUIRED CONFIG)
find_package(Clang REQUIRED CONFIG)

set (CMAKE_CXX_STANDARD 17)
add_compile_options(-Wall -pedantic -fPIC)

include_directories(${LLVM_INCLUDE_DIRS})
include_directories(${CLANG_INCLUDE_DIRS})

add_executable(Compiler CompilerModule.cpp)

# Link against LLVM libraries
target_link_libraries(Compiler embind)
target_link_libraries(Compiler clangInterpreter)

target_link_options(Compiler PRIVATE
    -O1
    -fexceptions
    -msimd128
    -sMODULARIZE
    -sEXPORT_ES6=1
    -sASSERTIONS=1
    -sNO_DISABLE_EXCEPTION_CATCHING
    -sALLOW_MEMORY_GROWTH=1
    -sINITIAL_MEMORY=128MB
    -sTOTAL_STACK=32MB
    -sMAIN_MODULE=1
    -sUSE_SDL=2
    -sEXPORTED_RUNTIME_METHODS=ccall,cwrap,stringToNewUTF8,getValue,setValue
    -sEXPORTED_FUNCTIONS=_malloc,_free,__ZTIN10emscripten3valE
    "-Wl,--export=__clang_Interpreter_SetValueNoAlloc"
    --preload-file /Users/anutosh491/micromamba/envs/xeus-cpp-wasm-build/opt/emsdk/upstream/emscripten/cache/sysroot/@/
    --profiling-funcs
)

Now as you can see I did add -msimd128 as a link option above but that still gets me to

So the only thing I am guessing is left here is llvm. Do I need to built that with the -msimd128 flag too ?
Not sure if any changes are required on xsimd (I see for running tests we build using this flag)

xsimd/test/CMakeLists.txt

Lines 221 to 227 in 6d6067a

	if(EMSCRIPTEN)
	set_target_properties(test_xsimd PROPERTIES LINK_FLAGS "-s MODULARIZE=1 -s EXPORT_NAME=test_xsimd_wasm -s WASM=1 -s ALLOW_MEMORY_GROWTH=1 -lembind")
	target_compile_options(test_xsimd
	PUBLIC --std=c++14
	PUBLIC "SHELL: -msimd128"
	PUBLIC "SHELL: -msse2"
	)

The recipe is present here if we want to look into any changes as to how xsimd is built (https://github.com/emscripten-forge/recipes/tree/main/recipes/recipes_emscripten/xsimd)

[serge-sans-paille]

I'd give it a try, yes

[serge-sans-paille]

Hey @anutosh491, any other way I can help?

[anutosh491]

Hey @serge-sans-paille ,

I think I was finally able to get around this 😄 (we had the -msimd128 flag missing at a crucial location that I was able to recognize)

Here is me trying xsimd with a simple html page running clang-repl in the browser (which is a toy project I use for debugging)

I shall extrapolate the same in xeus-cpp-lite.

And then Johan and I were talking about providing a link in xsimd's readme where it is enabled through xeus-cpp-lite so anyone can try out simd in the browser through xsimd which I think should be fun :)

Following that we can close this issue I think !

[anutosh491]

Was able to extrapolate it to xeus-cpp-lite

I'll work towards providing a link soon so that users can try xsimd's wasm architecture directly with xeus-cpp-lite (this link can lie in the readme for xsimd)

[serge-sans-paille]

That's super cool! I'll make sure to add the link once you have it. Congrats!