[llvm-dev] TryToShrinkGlobalToBoolean in GlobalOpt.cpp issue

[Ryan Taylor via llvm-dev]

Yes, the full test case is:

static int x = 100;
int y = whatever;

int main() {
   x = -101;
   y = whatever that's not whatever above;
   printf("%d\n", y);
   printf("%d\n", x);
  return 0;
}

You are correct, in the above test case the globalopt does not make the
transformation.... however, I think the original issue still stands, it
really shouldn't be doing it here either.

On Tue, Aug 30, 2016 at 5:52 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:

>
> > On Aug 30, 2016, at 1:01 PM, Ryan Taylor via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > Given some code:
> >
> > static int x = 100;
> >
> > int main() {
> >    x = 101;
> >    printf("%d\n", x);
> > }
> >
> > results in:
> >
> > %0 = load i1
> > %1 = select %0, 101, 100
>
> If x is only touched in one function, I’d expect globlaopt to turn it into
> an alloca instead of leaving it global and shrinking it.
> Did you oversimplify the real case where you see this for the sake of the
> example here?
>
> —
> Mehdi
>
>
> > ...
> > ...
> >
> > 1) What architecture(s) does this benefit?
> > 2) What's the best way to circumvent this in the backend (currently I am
> just not allowing this opt function to run)? I have tried a few
> setOperationAction methods to no result. Rather not just comment out core
> code because it makes porting more difficult.
> >
> > -Ryan
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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