Compiler optimization#1

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fix-fix wants to merge 8 commits intomasterfrom

compiler-optimization

Commits on Nov 21, 2021

compiler: use more structured codegen for future optimizations
fix-fix
committed

Commits on Nov 22, 2021

compiler: write out only after full pass
fix-fix
committed

Commits on Nov 23, 2021

compiler: add basic useless negation optimization
fix-fix
committed