[Bug tree-optimization/108750] New: Loop unswitching fails for poly_int conditions

[Bug tree-optimization/108750] New: Loop unswitching fails for poly_int conditions

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108750

            Bug ID: 108750
           Summary: Loop unswitching fails for poly_int conditions
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rsandifo at gcc dot gnu.org
  Target Milestone: ---

Loop unswitching fails to handle:

#include <arm_sve.h>

void foo(int *x, int *y, int z) {
  for (int i = 0; i < 100; ++i)
    if (svcntb() >= 4)
      x[i] = y[i] + 1;
    else
      y[i] += 1;
}

(although it does of course handle the result of replacing svcntb() with a
variable).  From a quick check, simply removing:

      /* At least the LHS needs to be symbolic.  */
      if (TREE_CODE (gimple_cond_lhs (stmt)) != SSA_NAME)
        return;

seems to fix it, but I've no idea what the fallout of that would be.

[Bug tree-optimization/108750] Loop unswitching fails for poly_int conditions

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108750

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-02-10

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
probably needs some other guards in strathegic places, other than that there's
no reason it shouldn't work ...