P is not a function: when compiling with -Os and ASM_JS=1

[simon-jentzsch]

If I compile my project as release ( -O2) the js-file is about 1MB and all tests pass, but using -Os reduces the size to 600k, but when running the tests some function names git wrong and I get an exception `P is not a function``

the linkinig command uses those options:

emcc -DNDEBUG -Os  -s ALLOW_MEMORY_GROWTH=1  -s FINALIZE_ASM_JS=1 -s NODEJS_CATCH_REJECTION=0  -s SEPARATE_ASM=1 -s WASM=0 -s ASM_JS=1 -s EXPORT_NAME=in3w  -s FILESYSTEM=0 -s  'EXTRA_EXPORTED_RUNTIME_METHODS=["ccall", "cwrap"]' -s SINGLE_FILE=1 -s MALLOC=emmalloc @CMakeFiles/in3w.dir/objects1.rsp  -o bin/in3w.js 

as sdk I'm using latest-upstream (1.39.18 node-12.9.1-64bit)

To reproduce:

git clone --single-branch --branch develop https://github.com/slockit/in3-c.git
cd in3-c

mkdir build
cd build

emcmake cmake -DWASM=true -DASMJS=true -DWASM_EMMALLOC=true  -DCMAKE_BUILD_TYPE=MINSIZEREL .. 
make -j8 in3_wasm
make test

(building it with -DCMAKE_BUILD_TYPE=RELEASE works fine)

[kripken]

Thanks @simon-jentzsch ! This turned out to be a bug in binaryen, fix is in WebAssembly/binaryen#2926

What happens is when optimizing for size we do metadce. That removes getTempRet0 in this case. But wasm2js then legalizes some internal stuff that adds a new import, which then breaks. The fix removes creation of new imports at that stage, which we don't need.

[kripken]

Fixed by that PR.

[simon-jentzsch]

thanks