[committed] Minor logic cleanup in get_range_strlen

[Jeff Law]

Just a trivial cleanup from Martin's work.

if (x == CONST)
  do something;
else
  return value;

Turns into

if (x != CONST)
  return value;
do something;


Again no behavior changes, but makes it easier to find the nuggets in
the rest of Martin's work.

Bootstrapped, regression tested on x86_64 and installed on the trunk.

jeff

ps. We're just about done with this stuff :-)  The holidays are both a
blessing and a curse when it comes to wrapping up something like this...

commit 0d90d6a22287cecf0c509336005cfd6c27560c67
Author: Jeff Law <l...@torsion.usersys.redhat.com>
Date:   Fri Dec 21 14:23:49 2018 -0500

            * gimple-fold.c (get_range_strlen): Minor logic cleanup.  Add 
comments
            on code's intent.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1ee865e1de8..54585381cbe 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,9 @@
 2018-12-30  Martin Sebor  <mse...@redhat.com>
            Jeff Law  <l...@redhat.com>
 
+       * gimple-fold.c (get_range_strlen): Minor logic cleanup.  Add comments
+       on code's intent.
+
        * gimple-fold.c (strlen_range_kind): New enum.
        (get_range_strlen): Update signature to use strlen_range_kind
        instead of type+fuzzy.
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 76fa328703c..fb43552bc35 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -1548,10 +1548,17 @@ get_range_strlen (tree arg, tree length[2], bitmap 
*visited,
              if (!get_range_strlen (ops[i], length, visited, rkind,
                                     flexp, eltsize, nonstr))
                {
-                 if (rkind == SRK_LENRANGE_2)
-                   *maxlen = build_all_ones_cst (size_type_node);
-                 else
+                 if (rkind != SRK_LENRANGE_2)
                    return false;
+                 /* Set the upper bound to the maximum to prevent
+                    it from being adjusted in the next iteration but
+                    leave MINLEN and the more conservative MAXBOUND
+                    determined so far alone (or leave them null if
+                    they haven't been set yet).  That the MINLEN is
+                    in fact zero can be determined from MAXLEN being
+                    unbounded but the discovered minimum is used for
+                    diagnostics.  */
+                 *maxlen = build_all_ones_cst (size_type_node);
                }
            return true;
          }
@@ -1576,10 +1583,17 @@ get_range_strlen (tree arg, tree length[2], bitmap 
*visited,
            if (!get_range_strlen (arg, length, visited, rkind, flexp,
                                   eltsize, nonstr))
              {
-               if (rkind == SRK_LENRANGE_2)
-                 *maxlen = build_all_ones_cst (size_type_node);
-               else
+               if (rkind != SRK_LENRANGE_2)
                  return false;
+               /* Set the upper bound to the maximum to prevent
+                  it from being adjusted in the next iteration but
+                  leave MINLEN and the more conservative MAXBOUND
+                  determined so far alone (or leave them null if
+                  they haven't been set yet).  That the MINLEN is
+                  in fact zero can be determined from MAXLEN being
+                  unbounded but the discovered minimum is used for
+                  diagnostics.  */
+               *maxlen = build_all_ones_cst (size_type_node);
              }
           }
         return true;