Updates to Python 2.7.4 and emscripten of Arp 29 2013 with le32 Go to js dir, run EMCONFIGURE_JS=1 ~/Dev/emscripten/emconfigure ./configure --without-threads --without-pymalloc --enable-shared --disable-ipv6 clean out MULTIARCH= in Makefile make, until error on pgen Go to native, run ./configure --without-threads --without-pymalloc --enable-shared --disable-ipv6 cp Parser/pgen ../JS_DIR/Parser return to JS chmod +x Parser/pgen remove #defines of DOUBLE_IS_BIG_ENDIAN_IEEE754 and DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754 and HAVE_GCC_ASM_FOR_X87 in pyconfig.h make link libpython2.7.so with Modules/python.o to get the bitcode file you want ========================= This is Python 2.7.2, compiled to .bc as follows: Uncompress Python into two separate directories, one for native and one for JS. In the JS one, do emconfigure ./configure --without-threads --without-pymalloc --enable-shared EDIT pyconfig.h, remove HAVE_GCC_ASM_FOR_X87 HAVE_SIG* except SIGNAL_H and *add* #define PY_NO_SHORT_FLOAT_REPR make It will fail on lack of permissions to run Parser/pgen. Go to the native one, do ./configure --without-threads --without-pymalloc make (Note: you don't need to let it complete, just enough for Parse/pgen is sufficient.) cp Parser/pgen ../YOUR_JS_DIR/Parser/ Return to the JS one, do chmod +x Parser/pgen make You will get an error on lack of permissions to run ./python. Ignore that, and do llvm-link libpython2.7.so python -o python.bc That's it! Thanks to rasjidw for helping with this!