Structural Analysis

[longfangsong]

Is your feature request related to a problem? Please describe.

Currently the wasm code gen is worked in a very unnature way.

And the code is very very very ugly.

Describe the solution you'd like

Instead of using current complex algorithm, use Structural Analysis based way instead.

We should start from creating a structural analysis analysis pass.

Ref Advanced Compiler Design & Implementation, Chapter 7.7, P202

Describe alternatives you've considered
Just refactor the current code generating.

[longfangsong]

#59 added the analysis, but need to use it to replace the scc based code gen process.