CODEWITHSUNDEEP
webassemblyemscriptenrust-wasm
Dr. Andrew Burnett-Thompson
Dr. Andrew Burnett-Thompson

Reputation: 21521

Twiggy command line options for emcc / emscripten to get meaningful data out

I'm using Twiggy from the Rust Wasm Toolchain to analyse a webassembly package to find largest contributors to code size.

Command line option

twiggy top -n 20 myWasm.wasm results in a table output like this:

 Shallow Bytes │ Shallow % │ Item
───────────────┼───────────┼──────────────────────
        520804 ┊    19.30% ┊ data[0]
         23612 ┊     0.87% ┊ code[17981]
         11360 ┊     0.42% ┊ code[26365]
         10709 ┊     0.40% ┊ code[26298]
         10640 ┊     0.39% ┊ elem[0]
         10040 ┊     0.37% ┊ data[1]
          9229 ┊     0.34% ┊ code[26356]
          9222 ┊     0.34% ┊ code[26364]
          8566 ┊     0.32% ┊ code[26598]
          8416 ┊     0.31% ┊ code[26363]
          8250 ┊     0.31% ┊ code[26329]
          8062 ┊     0.30% ┊ code[26355]
          7641 ┊     0.28% ┊ code[8133]
          7528 ┊     0.28% ┊ code[7927]
          7443 ┊     0.28% ┊ code[15443]
          7327 ┊     0.27% ┊ code[26728]
          7049 ┊     0.26% ┊ code[26729]
          7022 ┊     0.26% ┊ code[15921]
          6856 ┊     0.25% ┊ code[26588]
          6772 ┊     0.25% ┊ code[9434]
       2002166 ┊    74.19% ┊ ... and 29258 more.
       2698714 ┊   100.00% ┊ Σ [29278 Total Rows]

Obviously not very useful!

My current emcc command line args

emcc   -s WASM=1 --bind --closure 1 --no-heap-copy -s USE_SDL=2 -s FETCH=1 -s ALLOW_MEMORY_GROWTH=1  
  -s MAX_WEBGL_VERSION=2 -s ERROR_ON_UNDEFINED_SYMBOLS=0 -O0  -s MODULARIZE=1 -s NODEJS_CATCH_REJECTION=0 
  -s ENVIRONMENT=web

I'm guessing i need to have the right command line parameters to emcc (emscripten) during build to get some meaningful data here, but what?

I already turned off optimisations with -O0. Should it be a debug build?

Upvotes: 2

Views: 115

Answers (1)

MPlanchard
MPlanchard

Reputation: 1948

Was running into this issue with wasm-opt, and found that the -g option works well to preserve the necessary information. It looks like emcc supports the same option!

Upvotes: 1

Related Questions