[PATCH 2/2] dfa: simplify constraint-dependency checking

[Paul Eggert]

* lib/dfa.c (prev_newline_constraint, prev_letter_constraint)
(prev_other_constraint): Remove.
(prev_newline_dependent, prev_letter_dependent):
Simplify, to avoid an unnecessary bitwise AND operation.
---
 ChangeLog |  6 ++++++
 lib/dfa.c | 22 ++--------------------
 2 files changed, 8 insertions(+), 20 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 85436e1..2b8cbc1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2017-01-01  Paul Eggert  <address@hidden>
 
+       dfa: simplify constraint-dependency checking
+       * lib/dfa.c (prev_newline_constraint, prev_letter_constraint)
+       (prev_other_constraint): Remove.
+       (prev_newline_dependent, prev_letter_dependent):
+       Simplify, to avoid an unnecessary bitwise AND operation.
+
        dfa: prefer functions and constants to macros
        * lib/dfa.c: Prefer constants to macros where either will do.
        (streq, isasciidigit, newline_constraint)
diff --git a/lib/dfa.c b/lib/dfa.c
index 5b9de53..cd600aa 100644
--- a/lib/dfa.c
+++ b/lib/dfa.c
@@ -175,33 +175,15 @@ succeeds_in_context (int constraint, int prev, int curr)
 }
 
 /* The following describe what a constraint depends on.  */
-static int
-prev_newline_constraint (int constraint)
-{
-  return (constraint >> 2) & 0x111;
-}
-static int
-prev_letter_constraint (int constraint)
-{
-  return (constraint >> 1) & 0x111;
-}
-static int
-prev_other_constraint (int constraint)
-{
-  return constraint & 0x111;
-}
-
 static bool
 prev_newline_dependent (int constraint)
 {
-  return (prev_newline_constraint (constraint)
-          != prev_other_constraint (constraint));
+  return ((constraint ^ constraint >> 2) & 0x111) != 0;
 }
 static bool
 prev_letter_dependent (int constraint)
 {
-  return (prev_letter_constraint (constraint)
-          != prev_other_constraint (constraint));
+  return ((constraint ^ constraint >> 1) & 0x111) != 0;
 }
 
 /* Tokens that match the empty string subject to some constraint actually
-- 
2.7.4