stmt.c (expand_end_case): Index jumptables from zero for suitably small values of...

        * stmt.c (expand_end_case): Index jumptables from zero for
        suitably small values of minval.

From-SVN: r46478

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f704e4a..1dfc939 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2001-10-24  Roger Sayle <roger@eyesopen.com>
+ 
+       * stmt.c (expand_end_case): Index jumptables from zero for
+       suitably small values of minval.
+
 2001-10-24  Jakub Jelinek  <jakub@redhat.com>
 
        * stor-layout.c (place_union_field): If any field was aligned with

diff --git a/gcc/stmt.c b/gcc/stmt.c
index 4943397..76fa439 100644 (file)
--- a/gcc/stmt.c
+++ b/gcc/stmt.c
@@ -5534,6 +5534,17 @@ expand_end_case (orig_index)
                            table_label, default_label))
            {
              index_type = thiscase->data.case_stmt.nominal_type;
+
+              /* Index jumptables from zero for suitable values of
+                 minval to avoid a subtraction.  */
+              if (! optimize_size
+                  && compare_tree_int (minval, 0) > 0
+                  && compare_tree_int (minval, 3) < 0)
+                {
+                  minval = integer_zero_node;
+                  range = maxval;
+                }
+
              if (! try_tablejump (index_type, index_expr, minval, range,
                                   table_label, default_label))
                abort ();
@@ -5541,7 +5552,7 @@ expand_end_case (orig_index)
          
          /* Get table of labels to jump to, in order of case index.  */
 
-         ncases = TREE_INT_CST_LOW (range) + 1;
+         ncases = tree_low_cst (range, 0) + 1;
          labelvec = (rtx *) alloca (ncases * sizeof (rtx));
          memset ((char *) labelvec, 0, ncases * sizeof (rtx));