[Opt] Make full_simplify iterative when advanced_optimization=True

[xumingkuan]

Related issue = N/A

This PR offers shorter compilation time when advanced_optimization=False (by removing a full_simplify pass), and makes full_simplify more "full simplified".

Benchmark: the running time of a large program.

• advanced_optimization=True:
  • Before: total running time = 6m51s, compilation time of a large kernel = 6m37s

    codegen_accessor_statements: 148.00
    codegen_evaluator_statements: 102.00
    codegen_kernel_statements: 29020.00
    codegen_offloaded_tasks: 53.00
    codegen_statements  : 29270.00
    

  • After: total running time = 6m51s, compilation time of a large kernel = 6m35s

    codegen_accessor_statements: 148.00
    codegen_evaluator_statements: 102.00
    codegen_kernel_statements: 29020.00
    codegen_offloaded_tasks: 53.00
    codegen_statements  : 29270.00
    

• advanced_optimization=False:
  • Before: total running time = 3m21s, compilation time of a large kernel = 3m7s

    codegen_accessor_statements: 175.00
    codegen_kernel_statements: 59287.00
    codegen_offloaded_tasks: 41.00
    codegen_statements  : 59462.00
    

  • After: total running time = 2m59s, compilation time of a large kernel = 2m46s

    codegen_accessor_statements: 175.00
    codegen_kernel_statements: 59288.00
    codegen_offloaded_tasks: 42.00
    codegen_statements  : 59463.00
    

TODO (not urgent): make each IR transform pass return whether it modifies the IR (can be done together with #1059 )

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[xumingkuan]

Why didn't CI rerun when a worker crashed? All tests passed on my laptop.

[TH3CHARLie]

Looks great! I'll later rebase my local PR for #938 on master once this is merged. And you may push an empty commit to retrigger CI(I encountered the same appveyor issue two days ago).

[archibate]

throw-less treatment in full_simplify LGTM!

[codecov]

Codecov Report

Merging #1225 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1225   +/-   ##
=======================================
  Coverage   67.09%   67.09%           
=======================================
  Files          35       35           
  Lines        4835     4835           
  Branches      886      886           
=======================================
  Hits         3244     3244           
  Misses       1417     1417           
  Partials      174      174           

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