expr.c (do_jump_for_compare): Handle conditional branch expanders emitting multiple jump instructions.

        * expr.c (do_jump_for_compare): Handle conditional branch expanders
        emitting multiple jump instructions.
        * jump.c (condjump_label): New function.
        * rtl.h (condjump_label): Declare it.

From-SVN: r24773

4 files changed, 84 insertions, 21 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index bfd8a0b..572ce6c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+Tue Jan 19 21:20:52 1999  Richard Henderson  <rth@cygnus.com>
+
+	* expr.c (do_jump_for_compare): Handle conditional branch expanders
+	emitting multiple jump instructions.
+	* jump.c (condjump_label): New function.
+	* rtl.h (condjump_label): Declare it.
+
 Tue Jan 19 21:08:20 1999  Richard Henderson  <rth@cygnus.com>
 
 	* expr.c (emit_move_insn_1): Revert 17 Dec change.  Don't emit
diff --git a/gcc/expr.c b/gcc/expr.c
index 88ce156..591c826 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -11008,7 +11008,8 @@ do_jump_for_compare (comparison, if_false_label, if_true_label)
   if (if_true_label)
     {
       if (bcc_gen_fctn[(int) GET_CODE (comparison)] != 0)
-	emit_jump_insn ((*bcc_gen_fctn[(int) GET_CODE (comparison)]) (if_true_label));
+	emit_jump_insn ((*bcc_gen_fctn[(int) GET_CODE (comparison)])
+			  (if_true_label));
       else
 	abort ();
 
@@ -11017,52 +11018,80 @@ do_jump_for_compare (comparison, if_false_label, if_true_label)
     }
   else if (if_false_label)
     {
-      rtx insn;
-      rtx prev = get_last_insn ();
-      rtx branch = 0;
+      rtx first = get_last_insn (), insn, branch;
+      int br_count;
 
       /* Output the branch with the opposite condition.  Then try to invert
 	 what is generated.  If more than one insn is a branch, or if the
 	 branch is not the last insn written, abort. If we can't invert
 	 the branch, emit make a true label, redirect this jump to that,
 	 emit a jump to the false label and define the true label.  */
+      /* ??? Note that we wouldn't have to do any of this nonsense if
+	 we passed both labels into a combined compare-and-branch. 
+	 Ah well, jump threading does a good job of repairing the damage.  */
 
       if (bcc_gen_fctn[(int) GET_CODE (comparison)] != 0)
-	emit_jump_insn ((*bcc_gen_fctn[(int) GET_CODE (comparison)])(if_false_label));
+	emit_jump_insn ((*bcc_gen_fctn[(int) GET_CODE (comparison)])
+			  (if_false_label));
       else
 	abort ();
 
-      /* Here we get the first insn that was just emitted.  It used to be  the
+      /* Here we get the first insn that was just emitted.  It used to be the
 	 case that, on some machines, emitting the branch would discard
 	 the previous compare insn and emit a replacement.  This isn't
 	 done anymore, but abort if we see that PREV is deleted.  */
 
-      if (prev == 0)
-	insn = get_insns ();
-      else if (INSN_DELETED_P (prev))
+      if (first == 0)
+	first = get_insns ();
+      else if (INSN_DELETED_P (first))
 	abort ();
       else
-	insn = NEXT_INSN (prev);
+	first = NEXT_INSN (first);
 
-      for (; insn; insn = NEXT_INSN (insn))
+      /* Look for multiple branches in this sequence, as might be generated
+	 for a multi-word integer comparison.  */
+
+      br_count = 0;
+      branch = NULL_RTX;
+      for (insn = first; insn ; insn = NEXT_INSN (insn))
 	if (GET_CODE (insn) == JUMP_INSN)
 	  {
-	    if (branch)
-	      abort ();
 	    branch = insn;
+	    br_count += 1;
 	  }
 
-      if (branch != get_last_insn ())
-	abort ();
+      /* If we've got one branch at the end of the sequence,
+	 we can try to reverse it.  */
 
-      JUMP_LABEL (branch) = if_false_label;
-      if (! invert_jump (branch, if_false_label))
+      if (br_count == 1 && NEXT_INSN (branch) == NULL_RTX)
 	{
-	  if_true_label = gen_label_rtx ();
-	  redirect_jump (branch, if_true_label);
-	  emit_jump (if_false_label);
-	  emit_label (if_true_label);
+	  rtx insn_label;
+	  insn_label = XEXP (condjump_label (branch), 0);
+	  JUMP_LABEL (branch) = insn_label;
+
+	  if (insn_label != if_false_label)
+	    abort ();
+
+	  if (invert_jump (branch, if_false_label))
+	    return;
 	}
+
+      /* Multiple branches, or reversion failed.  Convert to branches
+	 around an unconditional jump.  */
+
+      if_true_label = gen_label_rtx ();
+      for (insn = first; insn; insn = NEXT_INSN (insn))
+	if (GET_CODE (insn) == JUMP_INSN)
+	  {
+	    rtx insn_label;
+	    insn_label = XEXP (condjump_label (insn), 0);
+	    JUMP_LABEL (insn) = insn_label;
+
+	    if (insn_label == if_false_label)
+	      redirect_jump (insn, if_true_label);
+	  }
+	emit_jump (if_false_label);
+	emit_label (if_true_label);
     }
 }
 
diff --git a/gcc/jump.c b/gcc/jump.c
index d5af17c..47f5fd4 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -3402,6 +3402,32 @@ condjump_in_parallel_p (insn)
   return 0;
 }
 
+/* Return the label of a conditional jump.  */
+
+rtx
+condjump_label (insn)
+     rtx insn;
+{
+  register rtx x = PATTERN (insn);
+
+  if (GET_CODE (x) == PARALLEL)
+    x = XVECEXP (x, 0, 0);
+  if (GET_CODE (x) != SET)
+    return NULL_RTX;
+  if (GET_CODE (SET_DEST (x)) != PC)
+    return NULL_RTX;
+  x = SET_SRC (x);
+  if (GET_CODE (x) == LABEL_REF)
+    return x;
+  if (GET_CODE (x) != IF_THEN_ELSE)
+    return NULL_RTX;
+  if (XEXP (x, 2) == pc_rtx && GET_CODE (XEXP (x, 1)) == LABEL_REF)
+    return XEXP (x, 1);
+  if (XEXP (x, 1) == pc_rtx && GET_CODE (XEXP (x, 2)) == LABEL_REF)
+    return XEXP (x, 2);
+  return NULL_RTX;
+}
+
 #ifdef HAVE_cc0
 
 /* Return 1 if X is an RTX that does nothing but set the condition codes
diff --git a/gcc/rtl.h b/gcc/rtl.h
index 0fef1a7..76fc6e1 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -1289,6 +1289,7 @@ extern void cse_end_of_basic_block	PROTO ((rtx,
 /* In jump.c */
 extern int comparison_dominates_p	PROTO ((enum rtx_code, enum rtx_code));
 extern int condjump_p			PROTO ((rtx));
+extern rtx condjump_label		PROTO ((rtx));
 extern int simplejump_p			PROTO ((rtx));
 extern int sets_cc0_p			PROTO ((rtx));
 extern int invert_jump			PROTO ((rtx, rtx));