ScottTodd/iree_emscripten.md

## iree_emscripten.md

      
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              iree_emscripten.md
            
          
    Goal: built iree-opt through emscripten to run it interactively from documentation websites.
See also: https://gist.github.com/ScottTodd/f30d9d26254de82648de37d5ed445cbc (mlir-opt through emscripten)
References:

Install emsdk: https://emscripten.org/docs/getting_started/downloads.html
Read https://emscripten.org/docs/compiling/Building-Projects.html
LLVM cross compilation: https://llvm.org/docs/HowToCrossCompileLLVM.html
LLVM CMake options: https://llvm.org/docs/CMake.html

Notes:

All commands are run from iree root directory (~/code/iree/ on my Linux machine)
Tested with IREE at https://github.com/google/iree/commit/ccae793f8c7c208a0b1b0baf489cfd121e5f7b4c
Tested with emsdk at https://github.com/emscripten-core/emsdk/commit/2e7eaf7233144e5e25b1c1338890bbab5d011815
Tested with cmake version 3.18.4 with clang 11 on Linux (Debian) after first trying on Windows with MSVC

Set up emsdk following those docs (run source ./emsdk_env.sh)
Build host tools:
cmake -G Ninja -B ../iree-build/ -DIREE_BUILD_TESTS=OFF -Wno-dev -DCMAKE_BUILD_TYPE=Release .
cmake --build ../iree-build/
cmake --build ../iree-build/ --target install

Configure for emscripten:
Note: we want to use the host tablegen and other tools throughout the build. Emscripten or LLVM creates a NATIVE/ folder
and tries to run tools from there... but the "executable binaries" in that directory are JavaScript files... which obviously can't be executed in a shell environment.
emcmake cmake -G Ninja -B ../iree-build-emscripten/ -DCMAKE_BUILD_TYPE=Release -DLLVM_TABLEGEN=$PWD/../iree-build/third_party/llvm-project/llvm/bin/llvm-tblgen -DMLIR_TABLEGEN_EXE=$PWD/../iree-build/third_party/llvm-project/llvm/bin/mlir-tblgen -DLLVM_TOOLS_BINARY_DIR=$PWD/../iree-build/third_party/llvm-project/llvm/bin/ -DIREE_HOST_BINARY_ROOT=$PWD/../iree-build/install/ -DIREE_BUILD_TESTS=OFF -DCMAKE_INSTALL_PREFIX=../iree-build/emscripten/install/ -Wno-dev .

** weird stuff happens here **
try building:
cmake --build ../iree-build-emscripten/ --target iree-opt.js

see errors about llvm-tblgen, mlir-tblgen, etc.
copy from host build to NATIVE/ folder:
cp ../iree-build/third_party/llvm-project/llvm/bin/llvm-tblgen ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin && chmod +x ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin/llvm-tblgen && cp ../iree-build/third_party/llvm-project/llvm/bin/mlir-tblgen ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin && chmod +x ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin/mlir-tblgen && cp ../iree-build/third_party/llvm-project/llvm/bin/mlir-linalg-ods-gen ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin && chmod +x ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin/mlir-linalg-ods-gen && cp ../iree-build/third_party/llvm-project/llvm/bin/mlir-linalg-ods-yaml-gen ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin && chmod +x ../iree-build-emscripten/third_party/llvm-project/llvm/NATIVE/bin/mlir-linalg-ods-yaml-gen

try building again:
cmake --build ../iree-build-emscripten/ --target iree-opt.js

maybe irrelevant, see errors about node and patch cmakecache:
edit iree-build-emscripten/CMakeCache.txt:
before:
CMAKE_CROSSCOMPILING_EMULATOR:UNINITIALIZED="/usr/local/google/home/scotttodd/code/emsdk/node/14.15.5_64bit/bin/node"

after:
CMAKE_CROSSCOMPILING_EMULATOR:UNINITIALIZED=/usr/local/google/home/scotttodd/code/emsdk/node/14.15.5_64bit/bin/node

notice that tblgen paths are not getting set correctly for HLO and IREE, hardcode TableGen.cmake:
  if (${project} STREQUAL "LLVM")
    set(${project}_TABLEGEN_EXE "/usr/local/google/home/scotttodd/code/iree/../iree-build/third_party/llvm-project/llvm/bin/llvm-tblgen")
  elseif(${project} STREQUAL "MLIR")
    set(${project}_TABLEGEN_EXE "/usr/local/google/home/scotttodd/code/iree/../iree-build/third_party/llvm-project/llvm/bin/mlir-tblgen")
  elseif(${project} STREQUAL "IREE")
    set(${project}_TABLEGEN_EXE "/usr/local/google/home/scotttodd/code/iree/../iree-build/install/bin/iree-tblgen")
  endif()

(see https://github.com/google/iree/blob/68c27a08f42ba64d566f7a6e4816550f6e0f57ae/build_tools/cmake/iree_copts.cmake#L449-L452)
wasm-ld: error: initial memory too small, 19770448 bytes needed
add
SET(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -s INITIAL_MEMORY=134217728")

at the bottom of iree_copts.cmake (number needs tuning)
success ?
ls -la ../iree-build-emscripten/iree/tools/

(should have iree-opt.js and iree-opt.wasm, among other files)