[PATCH] Hookize CASE_VALUES_THRESHOLD

[Anatoly Sokolov <aesok at post dot ru>]

Hello.

This patch turns CASE_VALUES_THRESHOLD into a hook.

The patch has been bootstrapped on i686-pc-linux-gnu and regression tested on
i686-pc-linux-gnu, avr (C) and m10300 (C).

Ok for mainline?

2008-03-24  Anatoly Sokolov  <aesok@post.ru>

        * target.h (struct gcc_target): Add case_values_threshold field.
        * target-def.h (TARGET_CASE_VALUES_THRESHOLD): New.
        (TARGET_INITIALIZER): Use TARGET_CASE_VALUES_THRESHOLD.
        * targhooks.c (default_case_values_threshold): New function.
        * targhooks.h (default_case_values_threshold): Declare function.
        * stmt.c (expand_case): Use case_values_threshold target hook.
        * expr.h (case_values_threshold): Remove declartation.
        * expr.c (case_values_threshold): Remove function.
        * doc/tm.texi (CASE_VALUES_THRESHOLD): Revise documentation.

        * config/avr/avr.h (CASE_VALUES_THRESHOLD): Remove macro.
        * config/avr/avr.c (TARGET_CASE_VALUES_THRESHOLD): Define macro.
        (avr_case_values_threshold): Declare as static.
        * config/avr/avr-protos.h (avr_case_values_threshold): Remove.

        * config/avr/mn10300.h (CASE_VALUES_THRESHOLD): Remove macro.
        * config/avr/mn10300.c (TARGET_CASE_VALUES_THRESHOLD): Define macro.
        (mn10300_case_values_threshold): New function.



Index: gcc/doc/tm.texi
===================================================================
--- gcc/doc/tm.texi     (revision 146309)
+++ gcc/doc/tm.texi     (working copy)
@@ -9712,12 +9712,12 @@
 is in effect.
 @end defmac
 
-@defmac CASE_VALUES_THRESHOLD
-Define this to be the smallest number of different values for which it
+@deftypefn {Target Hook} unsigned int TARGET_CASE_VALUES_THRESHOLD (void)
+This function return the smallest number of different values for which it
 is best to use a jump-table instead of a tree of conditional branches.
 The default is four for machines with a @code{casesi} instruction and
 five otherwise.  This is best for most machines.
-@end defmac
+@end deftypefn
 
 @defmac CASE_USE_BIT_TESTS
 Define this macro to be a C expression to indicate whether C switch
Index: gcc/targhooks.c
===================================================================
--- gcc/targhooks.c     (revision 146309)
+++ gcc/targhooks.c     (working copy)
@@ -765,4 +765,17 @@
   return ret;
 }
 
+#ifndef HAVE_casesi
+# define HAVE_casesi 0
+#endif
+
+/* If the machine does not have a case insn that compares the bounds,
+   this means extra overhead for dispatch tables, which raises the
+   threshold for using them.  */
+
+unsigned int default_case_values_threshold (void)
+{
+  return (HAVE_casesi ? 4 : 5);
+}
+
 #include "gt-targhooks.h"
Index: gcc/targhooks.h
===================================================================
--- gcc/targhooks.h     (revision 146309)
+++ gcc/targhooks.h     (working copy)
@@ -104,3 +104,4 @@
 extern bool default_target_option_valid_attribute_p (tree, tree, tree, int);
 extern bool default_target_option_pragma_parse (tree, tree);
 extern bool default_target_option_can_inline_p (tree, tree);
+extern unsigned int default_case_values_threshold (void);
Index: gcc/target.h
===================================================================
--- gcc/target.h        (revision 146309)
+++ gcc/target.h        (working copy)
@@ -919,6 +919,10 @@
      in peephole2.  */
   bool (* hard_regno_scratch_ok) (unsigned int regno);
 
+  /* Return the smallest number of different values for which it is best to
+     use a jump-table instead of a tree of conditional branches.  */
+  unsigned int (* case_values_threshold) (void);
+
   /* Functions specific to the C family of frontends.  */
   struct c {
     /* Return machine mode for non-standard suffix
Index: gcc/expr.c
===================================================================
--- gcc/expr.c  (revision 146309)
+++ gcc/expr.c  (working copy)
@@ -9886,19 +9886,6 @@
 # define CODE_FOR_casesi CODE_FOR_nothing
 #endif
 
-/* If the machine does not have a case insn that compares the bounds,
-   this means extra overhead for dispatch tables, which raises the
-   threshold for using them.  */
-#ifndef CASE_VALUES_THRESHOLD
-#define CASE_VALUES_THRESHOLD (HAVE_casesi ? 4 : 5)
-#endif /* CASE_VALUES_THRESHOLD */
-
-unsigned int
-case_values_threshold (void)
-{
-  return CASE_VALUES_THRESHOLD;
-}
-
 /* Attempt to generate a casesi instruction.  Returns 1 if successful,
    0 otherwise (i.e. if there is no casesi instruction).  */
 int
Index: gcc/expr.h
===================================================================
--- gcc/expr.h  (revision 146309)
+++ gcc/expr.h  (working copy)
@@ -583,10 +583,6 @@
 extern int try_casesi (tree, tree, tree, tree, rtx, rtx, rtx);
 extern int try_tablejump (tree, tree, tree, tree, rtx, rtx);
 
-/* Smallest number of adjacent cases before we use a jump table.
-   XXX Should be a target hook.  */
-extern unsigned int case_values_threshold (void);
-
 /* Functions from alias.c */
 #include "alias.h"
 
Index: gcc/target-def.h
===================================================================
--- gcc/target-def.h    (revision 146309)
+++ gcc/target-def.h    (working copy)
@@ -654,6 +654,10 @@
 #define TARGET_HARD_REGNO_SCRATCH_OK default_hard_regno_scratch_ok
 #endif
 
+#ifndef TARGET_CASE_VALUES_THRESHOLD
+#define TARGET_CASE_VALUES_THRESHOLD default_case_values_threshold
+#endif
+
 /* C specific.  */
 #ifndef TARGET_C_MODE_FOR_SUFFIX
 #define TARGET_C_MODE_FOR_SUFFIX default_mode_for_suffix
@@ -918,6 +922,7 @@
   TARGET_EXPAND_TO_RTL_HOOK,                   \
   TARGET_INSTANTIATE_DECLS,                    \
   TARGET_HARD_REGNO_SCRATCH_OK,                        \
+  TARGET_CASE_VALUES_THRESHOLD,                        \
   TARGET_C,                                    \
   TARGET_CXX,                                  \
   TARGET_EMUTLS,                               \
Index: gcc/config/avr/avr-protos.h
===================================================================
--- gcc/config/avr/avr-protos.h	(revision 146309)
+++ gcc/config/avr/avr-protos.h	(working copy)
@@ -39,7 +39,6 @@
 extern void gas_output_limited_string (FILE *file, const char *str);
 extern void gas_output_ascii (FILE *file, const char *str, size_t length);
 extern int avr_hard_regno_rename_ok (unsigned int, unsigned int);
-extern unsigned int avr_case_values_threshold (void);
 
 #ifdef TREE_CODE
 extern void asm_output_external (FILE *file, tree decl, char *name);
Index: gcc/config/avr/avr.c
===================================================================
--- gcc/config/avr/avr.c        (revision 146309)
+++ gcc/config/avr/avr.c        (working copy)
@@ -87,6 +87,7 @@
 static struct machine_function * avr_init_machine_status (void);
 static rtx avr_builtin_setjmp_frame_value (void);
 static bool avr_hard_regno_scratch_ok (unsigned int);
+static unsigned int avr_case_values_threshold (void);
 
 /* Allocate registers from r25 to r8 for parameters for function calls.  */
 #define FIRST_CUM_REG 26
@@ -359,6 +360,8 @@
 
 #undef TARGET_HARD_REGNO_SCRATCH_OK
 #define TARGET_HARD_REGNO_SCRATCH_OK avr_hard_regno_scratch_ok
+#undef TARGET_CASE_VALUES_THRESHOLD
+#define TARGET_CASE_VALUES_THRESHOLD avr_case_values_threshold
 
 struct gcc_target targetm = TARGET_INITIALIZER;
 
Index: gcc/config/avr/avr.h
===================================================================
--- gcc/config/avr/avr.h        (revision 146309)
+++ gcc/config/avr/avr.h        (working copy)
@@ -734,8 +734,6 @@
 
 #define CASE_VECTOR_MODE HImode
 
-#define CASE_VALUES_THRESHOLD avr_case_values_threshold ()
-
 #undef WORD_REGISTER_OPERATIONS
 
 #define MOVE_MAX 4
Index: gcc/config/mn10300/mn10300.c
===================================================================
--- gcc/config/mn10300/mn10300.c        (revision 146309)
+++ gcc/config/mn10300/mn10300.c        (working copy)
@@ -80,6 +80,7 @@
                                       const_tree, bool);
 static int mn10300_arg_partial_bytes (CUMULATIVE_ARGS *, enum machine_mode,
                                      tree, bool);
+static unsigned int mn10300_case_values_threshold (void);
 
 /* Initialize the GCC target structure.  */
 #undef TARGET_ASM_ALIGNED_HI_OP
@@ -119,6 +120,9 @@
 #undef TARGET_EXPAND_BUILTIN_VA_START
 #define TARGET_EXPAND_BUILTIN_VA_START mn10300_va_start
 
+#undef TARGET_CASE_VALUES_THRESHOLD
+#define TARGET_CASE_VALUES_THRESHOLD mn10300_case_values_threshold
+
 static void mn10300_encode_section_info (tree, rtx, int);
 struct gcc_target targetm = TARGET_INITIALIZER;
 
@@ -2126,3 +2130,15 @@
   if (flag_pic)
     SYMBOL_REF_FLAG (symbol) = (*targetm.binds_local_p) (decl);
 }
+
+/* Dispatch tables on the mn10300 are extremely expensive in terms of code
+   and readonly data size.  So we crank up the case threshold value to
+   encourage a series of if/else comparisons to implement many small switch
+   statements.  In theory, this value could be increased much more if we
+   were solely optimizing for space, but we keep it "reasonable" to avoid
+   serious code efficiency lossage.  */
+
+unsigned int mn10300_case_values_threshold (void)
+{
+  return 6;
+}
\ No newline at end of file
Index: gcc/config/mn10300/mn10300.h
===================================================================
--- gcc/config/mn10300/mn10300.h        (revision 146309)
+++ gcc/config/mn10300/mn10300.h        (working copy)
@@ -815,13 +815,7 @@
    than accessing full words.  */
 #define SLOW_BYTE_ACCESS 1
 
-/* Dispatch tables on the mn10300 are extremely expensive in terms of code
-   and readonly data size.  So we crank up the case threshold value to
-   encourage a series of if/else comparisons to implement many small switch
-   statements.  In theory, this value could be increased much more if we
-   were solely optimizing for space, but we keep it "reasonable" to avoid
-   serious code efficiency lossage.  */
-#define CASE_VALUES_THRESHOLD 6
+#define CASE_VALUES_THRESHOLD mn10300_case_values_threshold ()
 
 #define NO_FUNCTION_CSE
 
Index: gcc/stmt.c
===================================================================
--- gcc/stmt.c  (revision 146309)
+++ gcc/stmt.c  (working copy)
@@ -2320,7 +2320,7 @@
         If the switch-index is a constant, do it this way
         because we can optimize it.  */
 
-      else if (count < case_values_threshold ()
+      else if (count < targetm.case_values_threshold ()
               || compare_tree_int (range,
                                    (optimize_insn_for_size_p () ? 3 : 10) * count) > 0
               /* RANGE may be signed, and really large ranges will show up


Anatoly