[PATCH] ira: update allocated_hardreg_p[] in improve_allocation() [PR110254]

[Surya Kumari Jangala via Gcc-patches]

The improve_allocation() routine does not update the
allocated_hardreg_p[] array after an allocno is assigned a register.

If the register chosen in improve_allocation() is one that already has
been assigned to a conflicting allocno, then allocated_hardreg_p[]
already has the corresponding bit set to TRUE, so nothing needs to be
done.

But improve_allocation() can also choose a register that has not been
assigned to a conflicting allocno, and also has not been assigned to any
other allocno. In this case, allocated_hardreg_p[] has to be updated.

2023-07-21  Surya Kumari Jangala  <jskum...@linux.ibm.com>

gcc/
        PR rtl-optimization/PR110254
        * ira-color.cc (improve_allocation): Update array
---

diff --git a/gcc/ira-color.cc b/gcc/ira-color.cc
index 1fb2958bddd..5807d6d26f6 100644
--- a/gcc/ira-color.cc
+++ b/gcc/ira-color.cc
@@ -3340,6 +3340,10 @@ improve_allocation (void)
        }
       /* Assign the best chosen hard register to A.  */
       ALLOCNO_HARD_REGNO (a) = best;
+
+      for (j = nregs - 1; j >= 0; j--)
+       allocated_hardreg_p[best + j] = true;
+
       if (internal_flag_ira_verbose > 2 && ira_dump_file != NULL)
        fprintf (ira_dump_file, "Assigning %d to a%dr%d\n",
                 best, ALLOCNO_NUM (a), ALLOCNO_REGNO (a));