[Bug tree-optimization/93917] VRP forgets range of value read from memory

[Bug tree-optimization/93917] VRP forgets range of value read from memory

[amacleod at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93917

Andrew Macleod <amacleod at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amacleod at redhat dot com

--- Comment #2 from Andrew Macleod <amacleod at redhat dot com> ---
This seems to be a good place to bring up a question I have.

What exactly do we want to with __builtin_unreachable across passes?

Ranger was initially starting with the previously set globally known value, and
I had to disable it for pr61034.C

Basically, the routine was pre-optimized and inlined, and inlining sets the
global range based on the output from the optimizations, and when ranger
removed the code with the unreachable in it, the testcase failed.

so 
void f(int n){
  if(n<0)__builtin_unreachable();
}
n has a global range of [0, +INF]

Is that the basic point of this?  Can we set the global range to that and
eliminate the if?

same thing for 
  if(*n<0)__builtin_unreachable();

I see:
    _1 = *n_3(D);
    if (_1 < 0)
      goto <bb 3>; [INV]
    else
      goto <bb 4>; [INV]

2->3  (T) _1 :  int [-INF, -1]
2->4  (F) _1 :  int [0, +INF]

=========== BB 3 ============
    <bb 3> :
    __builtin_unreachable ();

And we can know that _1 is [0, +INF] from then on. 

Can we kill all these unreachables() the first time we see them if we set the
range appropriately?

If not, at what point do we want to kill them?

[Bug tree-optimization/93917] VRP forgets range of value read from memory

[amacleod at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93917

Andrew Macleod <amacleod at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Andrew Macleod <amacleod at redhat dot com> ---
Fixed by
commit e7310e24b1c0ca67b1bb507c1330b2bf39e59e32
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Tue Oct 25 16:42:41 2022 -0400

    Make ranger vrp1 default.

[Bug tree-optimization/93917] VRP forgets range of value read from memory

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93917

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.0

[Bug tree-optimization/93917] VRP forgets range of value read from memory

[amacleod at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93917

--- Comment #4 from Andrew Macleod <amacleod at redhat dot com> ---
Note a slight change in expectation as a result of commit
r14-4141-gbf6b107e2a342319b3787ec960fc8014ef3aff91  for PR 110080

Due to a memory load in the second case, we do not remove the unreachable call
now as there may be a commoning opportunity later (via inlining in this case)
in which this unreachable call may provide new information.

The test case has been adjusted to current expectations where we leave this
unreachable call and then remove it and set the global range in VRP2 instead.