How to implement passes of flang -O1(or -O3) using opt?

[zzhang77]

Currently, I am trying to mimic the O1 process of flang using opt, because I would like to disable some passes (vectorization passes and loop unrolling). And opt might be possible to implement O1 process without those passes.

I tried something like this
flang -O0 test.f90 -S -o test.ll

opt -sroa -early-cse -simplifycfg -instcombine -libcalls-shrinkwrap -simplifycfg -reassociate -loop-instsimplify -loop-simplifycfg -licm -loop-rotate -licm -simple-loop-unswitch -bdce -instcombine -simplifycfg -instcombine test.ll -S -o test-after.ll

But I'm not sure whether it is done correctly.
Any suggestions are welcomed. Thanks!

[bryanpkc]

Why don't you look into LLVM's pass pipeline, and disable the passes you don't need (by adding options)?