llvm dev - Jul 2016 - Running verify between every opt pass?

Hi,

Is there any easy way to run the verifier between each pass in opt if I 
do e.g. opt -O3 foo.ll -o foo.opt.ll ?

If I add -verify after -O3 I get one invocation of the verifier first in 
the FunctionPass manager and then get two (!) runs of the verifier after 
all other passes are run.

Then I saw the flag -verify-each which sounds promising, the help text says

  - Verify after each transform

but if I do

-O3 -verify-each

it still looks like the verifier is only run once, first in the 
FunctionPass manager?

Is there any way to do this somewhat easily?

(And the reason I got interested in this is that we've recently seen a 
bug in the loop-vectorizer where a verifer invocation would have 
complained, but without it the resulting code from opt was wrong which 
later caused the code to do the wrong thing at runtime.

And running a single verifier pass after all of the opt passes wouldn't 
have caught it either because some other pass had already rewritten the 
code by then so the verifier wouldn't complain anymore.)

Thanks,
Mikael

> On Jul 8, 2016, at 12:38 AM, Mikael Holmén via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi,
> 
> Is there any easy way to run the verifier between each pass in opt if I do
e.g. opt -O3 foo.ll -o foo.opt.ll ?
I don’t think so.
> 
> If I add -verify after -O3 I get one invocation of the verifier first in
the FunctionPass manager and then get two (!) runs of the verifier after all
other passes are run.
> 
> Then I saw the flag -verify-each which sounds promising, the help text says
> 
> - Verify after each transform
> 
> but if I do
> 
> -O3 -verify-each
> 
> it still looks like the verifier is only run once, first in the
FunctionPass manager?

The verify-each flag only works for passes that are specified on the command
line, it does not operate on O3.

> 
> Is there any way to do this somewhat easily?
As a workaround, you can get the list of passes that matches O3:

echo "" | opt -O3 -debug-pass=Arguments

And the re-run opt with all theses passes on the command line instead of O3.

— 
Mehdi


> 
> (And the reason I got interested in this is that we've recently seen a
bug in the loop-vectorizer where a verifer invocation would have complained, but
without it the resulting code from opt was wrong which later caused the code to
do the wrong thing at runtime.
> 
> And running a single verifier pass after all of the opt passes wouldn't
have caught it either because some other pass had already rewritten the code by
then so the verifier wouldn't complain anymore.)
> 
> Thanks,
> Mikael
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Mehdi, as you said yes this is a workaround but this is not portable and i
think the scenario mentioned here could occur in general. So running verify
pass after each pass is useful.. May be we should invoke verify pass after
each pass in O3 under an option say --verify-after-each? In other words,
opt will invoke verify pass after each pass only if the above option is
provided.
On Jul 8, 2016 11:31 PM, "Mehdi Amini via llvm-dev" <llvm-dev at
lists.llvm.org>
wrote:

> On Jul 8, 2016, at 12:38 AM, Mikael Holmén via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
>
> Hi,
>
> Is there any easy way to run the verifier between each pass in opt if I
do e.g. opt -O3 foo.ll -o foo.opt.ll ?

I don’t think so.
>
> If I add -verify after -O3 I get one invocation of the verifier first in
the FunctionPass manager and then get two (!) runs of the verifier after
all other passes are run.
>
> Then I saw the flag -verify-each which sounds promising, the help text
says
>
> - Verify after each transform
>
> but if I do
>
> -O3 -verify-each
>
> it still looks like the verifier is only run once, first in the
FunctionPass manager?


The verify-each flag only works for passes that are specified on the
command line, it does not operate on O3.

>
> Is there any way to do this somewhat easily?
As a workaround, you can get the list of passes that matches O3:

echo "" | opt -O3 -debug-pass=Arguments

And the re-run opt with all theses passes on the command line instead of O3.

—
Mehdi


>
> (And the reason I got interested in this is that we've recently seen a
bug in the loop-vectorizer where a verifer invocation would have
complained, but without it the resulting code from opt was wrong which
later caused the code to do the wrong thing at runtime.
>
> And running a single verifier pass after all of the opt passes wouldn't
have caught it either because some other pass had already rewritten the
code by then so the verifier wouldn't complain
anymore.)
>
> Thanks,
> Mikael
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
_______________________________________________
LLVM Developers mailing list
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http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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> On Jul 8, 2016, at 11:16 AM, Madhur Amilkanthwar <madhur13490 at
gmail.com> wrote:
> 
> Mehdi, as you said yes this is a workaround but this is not portable
> 
Not sure what you mean by “not portable”?
> and i think the scenario mentioned here could occur in general. So running
verify pass after each pass is useful.. May be we should invoke verify pass
after each pass in O3 under an option say --verify-after-each? In other words,
opt will invoke verify pass after each pass only if the above option is
provided.
> 
Patch welcome :)
Not sure what’s the best way to implement it though...

— 
Mehdi


> On Jul 8, 2016 11:31 PM, "Mehdi Amini via llvm-dev" <llvm-dev
at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> 
> > On Jul 8, 2016, at 12:38 AM, Mikael Holmén via llvm-dev <llvm-dev
at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> >
> > Hi,
> >
> > Is there any easy way to run the verifier between each pass in opt if
I do e.g. opt -O3 foo.ll -o foo.opt.ll ?
> 
> I don’t think so.
> 
> >
> > If I add -verify after -O3 I get one invocation of the verifier first
in the FunctionPass manager and then get two (!) runs of the verifier after all
other passes are run.
> >
> > Then I saw the flag -verify-each which sounds promising, the help text
says
> >
> > - Verify after each transform
> >
> > but if I do
> >
> > -O3 -verify-each
> >
> > it still looks like the verifier is only run once, first in the
FunctionPass manager?
> 
> 
> The verify-each flag only works for passes that are specified on the
command line, it does not operate on O3.
> 
> 
> >
> > Is there any way to do this somewhat easily?
> 
> As a workaround, you can get the list of passes that matches O3:
> 
> echo "" | opt -O3 -debug-pass=Arguments
> 
> And the re-run opt with all theses passes on the command line instead of
O3.
> 
> —
> Mehdi
> 
> 
> 
> >
> > (And the reason I got interested in this is that we've recently
seen a bug in the loop-vectorizer where a verifer invocation would have
complained, but without it the resulting code from opt was wrong which later
caused the code to do the wrong thing at runtime.
> >
> > And running a single verifier pass after all of the opt passes
wouldn't have caught it either because some other pass had already rewritten
the code by then so the verifier wouldn't complain anymore.)
> >
> > Thanks,
> > Mikael
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
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