bfin.c (branch_dest): Add comment why it's necessary.

	* config/bfin/bfin.c (branch_dest): Add comment why it's
	necessary.
	* config/bfin/bfin.md (attr "length" default): Change the offset of
	forward conditional branch of length 4 from 4096 to 4092.

Co-Authored-By: Bernd Schmidt <bernd.schmidt@analog.com>

From-SVN: r99966

gcc/ChangeLog

+2005-05-18  Jie Zhang  <jie.zhang@analog.com>
+            Bernd Schmidt  <bernd.schmidt@analog.com>
+
+	* config/bfin/bfin.c (branch_dest): Add comment why it's
+	necessary.
+	* config/bfin/bfin.md (attr "length" default): Change the offset of
+	forward conditional branch of length 4 from 4096 to 4092.
+
 2005-05-19  Jan Beulich  <jbeulich@novell.com>
 
 	* unwind-compat.c: Include tconfig.h and tsystem.h.

gcc/config/bfin/bfin.c

@@ -1751,7 +1751,10 @@ override_options (void)
   flag_schedule_insns = 0;
 }
 
-/* Return the destination address of BRANCH.  */
+/* Return the destination address of BRANCH.
+   We need to use this instead of get_attr_length, because the
+   cbranch_with_nops pattern conservatively sets its length to 6, and
+   we still prefer to use shorter sequences.  */
 
 static int
 branch_dest (rtx branch)

gcc/config/bfin/bfin.md

@@ -173,7 +173,9 @@
 ;;;   if cc jmp; jump.[sl] offset
 ;;;   offset of jump.[sl] is from the jump instruction but
 ;;;     gcc calculates length from the if cc jmp instruction
-;;;     hence our range is (-4094, 4096) instead of (-4096, 4094) for a br
+;;;     furthermore gcc takes the end address of the branch instruction
+;;;     as (pc) for a forward branch
+;;;     hence our range is (-4094, 4092) instead of (-4096, 4094) for a br
 ;;;
 ;;; The way the (pc) rtx works in these calculations is somewhat odd;
 ;;; for backward branches it's the address of the current instruction,
@@ -210,7 +212,7 @@
 	            (ge (minus (match_dup 3) (pc)) (const_int -1024)))
 		  (const_int 2)
 		(and
-	            (le (minus (match_dup 3) (pc)) (const_int 4096))
+	            (le (minus (match_dup 3) (pc)) (const_int 4092))
 	            (ge (minus (match_dup 3) (pc)) (const_int -4094)))
 		  (const_int 4)]
 	       (const_int 6))