[Bug target/92908] [10 Regression] wrong code with -Og -fno-tree-fre -mavx512bw and vector compare

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92908

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2019-12-11
                 CC|                            |jakub at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org
   Target Milestone|---                         |10.0
     Ever confirmed|0                           |1

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
--- gcc/simplify-rtx.c.jj       2019-11-19 22:27:02.000058742 +0100
+++ gcc/simplify-rtx.c  2019-12-11 13:31:57.197809704 +0100
@@ -5037,6 +5037,23 @@ simplify_relational_operation (enum rtx_
          return NULL_RTX;
 #endif
        }
+      if (VECTOR_MODE_P (cmp_mode)
+         && SCALAR_INT_MODE_P (mode)
+         && tem == const_true_rtx)
+       {
+         /* Vector comparisons that expect a scalar integral
+            bitmask.  For const0_rtx the result is already correct,
+            for const_true_rtx we need all bits set.  */
+         int n_elts;
+         scalar_int_mode smode = as_a <scalar_int_mode> (mode);
+         gcc_assert (GET_MODE_NUNITS (cmp_mode).is_constant (&n_elts)
+                     && GET_MODE_PRECISION (smode) <= n_elts);
+         if (GET_MODE_PRECISION (smode) == n_elts)
+           return constm1_rtx;
+         if (n_elts < HOST_BITS_PER_WIDE_INT)
+           return GEN_INT ((HOST_WIDE_INT_1U << n_elts) - 1);
+         return NULL_RTX;
+       }

       return tem;
     }
@@ -5383,7 +5400,7 @@ comparison_result (enum rtx_code code, i
 }

 /* Check if the given comparison (done in the given MODE) is actually
-   a tautology or a contradiction.  If the mode is VOID_mode, the
+   a tautology or a contradiction.  If the mode is VOIDmode, the
    comparison is done in "infinite precision".  If no simplification
    is possible, this function returns zero.  Otherwise, it returns
    either const_true_rtx or const0_rtx.  */

fixes this.