[llvm-dev] opt - replicating multiple passes from -O3 -debug-pass=Executions

[Chad Verbowski via llvm-dev]

Hello,

I am trying to replicate the output from opt -O3 foo.bc -o foo.opt.bc by
specifying the individual passes instead of the -O3 flag.

Looking at the passes from opt -O3 foo.bc -o foo.bc -debug-pass=Executions
it seems there are two passes being run. When I run the flags indicated for
the two passes specified in the 'Pass Arguments:' as two sequential opt
processes or a single opt process with the concatenated flags  I get a
different binary result compared to the O3 run. (Note I had to remove the
-targetpassconfig flag and add -spec-exec-only-if-divergent-target to the
second pass to get my run to match O3's second pass.)

Comparing the -debug-pass=Executions from my runs with the O3 run, it seems
the first pass in my run has additional 'TargetLibrary Information',
'Target Pass Configuration' and the 'Module Pass Manager' entries compared
to O3 (copied below). My output shows the 'Pass Arguments:' line has
automatically added  -targetpassconfig -verify -writebitcode, and the
-targetlibinfo flag was moved to the start.

Is there a way I can address these differences to enable replicating the
-O3 first and second passes using opt flags?

Thanks for considering this,

-Chad

(Opt -O3 first pass) Pass Arguments:  -tti -tbaa -scoped-noalias
-assumption-cache-tracker -targetlibinfo -verify -ee-instrument
-simplifycfg -domtree -sroa -early-cse -lower-expect
Target Transform Information
Type-Based Alias Analysis
Scoped NoAlias Alias Analysis
Assumption Cache Tracker
Target Library Information
  FunctionPass Manager
    Module Verifier
    Instrument function entry/exit with calls to e.g. mcount() (pre
inlining)
    Simplify the CFG
    Dominator Tree Construction
    SROA
    Early CSE
    Lower 'expect' Intrinsics

(My Run): opt in.bc -o out.bc -debug-pass=Executions  -tti -tbaa
-scoped-noalias -assumption-cache-tracker -targetlibinfo -verify
-ee-instrument -simplifycfg -domtree -sroa -early-cse -lower-expect

Pass Arguments: * -targetlibinfo* -tti *-targetpassconfig* -tbaa
-scoped-noalias -assumption-cache-tracker -verify -ee-instrument
-simplifycfg -domtree -sroa -early-cse -lower-expect *-verify
-write-bitcode*
*Target Library Information*
Target Transform Information
Target Pass Configuration
Type-Based Alias Analysis
Scoped NoAlias Alias Analysis
Assumption Cache Tracker
  *ModulePass Manager*
    FunctionPass Manager
      Module Verifier
      Instrument function entry/exit with calls to e.g. mcount() (pre
inlining)
      Simplify the CFG
      Dominator Tree Construction
      SROA
      Early CSE
      Lower 'expect' Intrinsics
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