2001-07-13 Andrew Haley <aph@redhat.com>

        * doc/tm.texi (MD_CAN_REDIRECT_BRANCH): New macro.
        * config/sh/sh.h (MD_CAN_REDIRECT_BRANCH): New macro.
        * config/sh/sh.c (sh_can_redirect_branch): New function.
        * config/sh/sh-protos.h (sh_can_redirect_branch): Declare.
        * reorg.c (steal_delay_list_from_target): Use
        MD_CAN_REDIRECT_BRANCH to see if redirection is possible.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@44269 138bc75d-0d04-0410-961f-82ee72b054a4

6 files changed, 69 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 642408d7876..b49083981f8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2001-07-13  Andrew Haley  <aph@redhat.com>
+
+        * doc/tm.texi (MD_CAN_REDIRECT_BRANCH): New macro.
+        * config/sh/sh.h (MD_CAN_REDIRECT_BRANCH): New macro.
+        * config/sh/sh.c (sh_can_redirect_branch): New function.
+        * config/sh/sh-protos.h (sh_can_redirect_branch): Declare.
+        * reorg.c (steal_delay_list_from_target): Use
+        MD_CAN_REDIRECT_BRANCH to see if redirection is possible.
+
 Mon Jul 23 17:20:18 CEST 2001  Jan Hubicka  <jh@suse.cz>
 
 	* flow.c (try_simplify_condjump): Unlink insn chain on
diff --git a/gcc/config/sh/sh-protos.h b/gcc/config/sh/sh-protos.h
index 1200ba2f41a..f11f2e2f74b 100644
--- a/gcc/config/sh/sh-protos.h
+++ b/gcc/config/sh/sh-protos.h
@@ -98,6 +98,7 @@ extern void expand_df_unop PARAMS ((rtx (*)(rtx, rtx, rtx), rtx *));
 extern void expand_df_binop PARAMS ((rtx (*)(rtx, rtx, rtx, rtx), rtx *));
 extern void expand_fp_branch PARAMS ((rtx (*)(void), rtx (*)(void)));
 extern int sh_insn_length_adjustment PARAMS ((rtx));
+extern int sh_can_redirect_branch PARAMS ((rtx, rtx));
 #ifdef TREE_CODE
 extern void sh_va_start PARAMS ((int, tree, rtx));
 extern rtx sh_va_arg PARAMS ((tree, tree));
diff --git a/gcc/config/sh/sh.c b/gcc/config/sh/sh.c
index 18e6379fd60..ec09d08b666 100644
--- a/gcc/config/sh/sh.c
+++ b/gcc/config/sh/sh.c
@@ -5515,3 +5515,40 @@ static rtx mark_constant_pool_use (x)
 
   return lab;
 }
+
+/* Return true if it's possible to redirect BRANCH1 to the destination
+   of an unconditional jump BRANCH2.  We only want to do this if the
+   resulting branch will have a short displacement.  */
+int 
+sh_can_redirect_branch (branch1, branch2)
+     rtx branch1;
+     rtx branch2;
+{
+  if (flag_expensive_optimizations && simplejump_p (branch2))
+    {
+      rtx dest = XEXP (SET_SRC (single_set (branch2)), 0);
+      rtx insn;
+      int distance;
+      
+      for (distance = 0, insn = NEXT_INSN (branch1); 
+	   insn && distance < 256; 
+	   insn = PREV_INSN (insn))
+	{
+	  if (insn == dest)    
+	    return 1;
+	  else
+	    distance += get_attr_length (insn);
+	}
+      for (distance = 0, insn = NEXT_INSN (branch1); 
+	   insn && distance < 256; 
+	   insn = NEXT_INSN (insn))
+	{
+	  if (insn == dest)    
+	    return 1;
+	  else
+	    distance += get_attr_length (insn);
+	}
+    }
+  return 0;
+}
+
diff --git a/gcc/config/sh/sh.h b/gcc/config/sh/sh.h
index f72c07c9fbe..cc17258353f 100644
--- a/gcc/config/sh/sh.h
+++ b/gcc/config/sh/sh.h
@@ -2421,6 +2421,9 @@ do {									\
 #define EMIT_MODE_SET(ENTITY, MODE, HARD_REGS_LIVE) \
   fpscr_set_from_mem ((MODE), (HARD_REGS_LIVE))
 
+#define MD_CAN_REDIRECT_BRANCH(INSN, SEQ) \
+  sh_can_redirect_branch ((INSN), (SEQ))
+
 #define DWARF_LINE_MIN_INSTR_LENGTH 2
 
 /* SH constant pool breaks the devices in crtstuff.c to control section
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index b5d8ba92d4d..81a55828c2e 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -8681,4 +8681,15 @@ ignored.  This function should return the result of the call to the
 built-in function.
 @end deftypefn
 
+@findex MD_CAN_REDIRECT_BRANCH
+@item MD_CAN_REDIRECT_BRANCH(@var{branch1}, @var{branch2})
+
+Take a branch insn in @var{branch1} and a another in @var{branch2}.
+Return true if redirecting @var{branch1} to the destination of
+@var{branch2} is possible.
+
+On some targets, branches may have a limited range.  Optimizing the
+filling of delay slots can result in branches being redirected, and this
+may in turn cause a branch offset to overflow.
+
 @end table
diff --git a/gcc/reorg.c b/gcc/reorg.c
index 1f26e7e3751..3177e7117dd 100644
--- a/gcc/reorg.c
+++ b/gcc/reorg.c
@@ -1272,6 +1272,14 @@ steal_delay_list_from_target (insn, condition, seq, delay_list,
       || ! single_set (XVECEXP (seq, 0, 0)))
     return delay_list;
 
+#ifdef MD_CAN_REDIRECT_BRANCH
+  /* On some targets, branches with delay slots can have a limited
+     displacement.  Give the back end a chance to tell us we can't do
+     this.  */
+  if (! MD_CAN_REDIRECT_BRANCH (insn, XVECEXP (seq, 0, 0)))
+    return delay_list;
+#endif
+
   for (i = 1; i < XVECLEN (seq, 0); i++)
     {
       rtx trial = XVECEXP (seq, 0, i);