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Chad Verbowski via llvm-dev

2020-Aug-11 05:42 UTC

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

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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Chad Verbowski via llvm-dev

2020-Aug-11 17:14 UTC

head link

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

Update: Comparing the -print-before-all and -print-after-all for -O3 and
the run with the flags, I see a difference starting with the 7th (of 8)
"*** IR Dump After Simplify the CFG ***" which I assume is the
-simplifycfg
flag.

Is there any known reason -simplifycfg would behave differently if the
pipeline of passes up to this point  are identical (order and their input
and output)?

Thanks.


On Mon, Aug 10, 2020 at 10:42 PM Chad Verbowski <chad at verbowski.com>
wrote:
> 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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Sanjay Patel via llvm-dev

2020-Aug-12 12:12 UTC

head link

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

The pipeline built with -O3 includes non-default options for -simplifycfg
when it runs late. I don't know if it is possible to replicate that
behavior if you are trying to specify multiple runs of a pass via the
command-line options.

  // Cleanup after loop vectorization, etc. Simplification passes like CVP
and
  // GVN, loop transforms, and others have already run, so it's now better
to
  // convert to more optimized IR using more aggressive simplify CFG
options.
  // The extra sinking transform can create larger basic blocks, so do this
  // before SLP vectorization.
  // FIXME: study whether hoisting and/or sinking of common instructions
should
  //        be delayed until after SLP vectorizer.
  MPM.add(createCFGSimplificationPass(SimplifyCFGOptions()
                                          .forwardSwitchCondToPhi(true)
                                          .convertSwitchToLookupTable(true)
                                          .needCanonicalLoops(false)
                                          .hoistCommonInsts(true)
                                          .sinkCommonInsts(true)));



On Tue, Aug 11, 2020 at 1:14 PM Chad Verbowski via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Update: Comparing the -print-before-all and -print-after-all for -O3 and
> the run with the flags, I see a difference starting with the 7th (of 8)
> "*** IR Dump After Simplify the CFG ***" which I assume is the
-simplifycfg
> flag.
>
> Is there any known reason -simplifycfg would behave differently if the
> pipeline of passes up to this point  are identical (order and their input
> and output)?
>
> Thanks.
>
>
> On Mon, Aug 10, 2020 at 10:42 PM Chad Verbowski <chad at
verbowski.com>
> wrote:
>
>> 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
>>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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