[PATCH 1/2, rs6000] Add const_anchor for rs6000 [PR33699]

[HAO CHEN GUI via Gcc-patches]

Hi,

    This patch adds const_anchor for rs6000. The const_anchor is used 
in cse pass.

    The attachment are the patch diff and change log file.

    Bootstrapped and tested on powerpc64le with no regressions. Is this 
okay for trunk? Any  recommendations? Thanks a lot.

        * config/rs6000/rs6000.c (rs6000_option_override_internal): Set
        targetm.const_anchor, targetm.min_anchor_offset
        and targetm.max_anchor_offset.
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index ec068c58aa5..2b2350c53ae 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -4911,6 +4911,13 @@ rs6000_option_override_internal (bool global_init_p)
     warning (0, "%qs is deprecated and not recommended in any circumstances",
             "-mno-speculate-indirect-jumps");
 
+  if (TARGET_64BIT)
+    {
+      targetm.min_anchor_offset = -32768;
+      targetm.max_anchor_offset = 32767;
+      targetm.const_anchor = 0x8000;
+    }
+
   return ret;
 }