* jump.c (jump_optimize_1): When we delete a conditional jump

preceeding a non-conditional jump to effectively the same place,
make sure that the combined jump skips any clobber insns between
the two labels.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@39686 138bc75d-0d04-0410-961f-82ee72b054a4

2 files changed, 30 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 63bbb9bff3f..a97e22abc24 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2001-02-14  Richard Henderson  <rth@redhat.com>
+	    DJ Delorie  <dj@redhat.com>
+
+	* jump.c (jump_optimize_1): When we delete a conditional jump
+	preceeding a non-conditional jump to effectively the same place,
+	make sure that the combined jump skips any clobber insns between
+	the two labels.
+
 2001-02-14  Jeffrey Oldham  <oldham@codesourcery.com>
 
 	* gcc.c (do_spec_1): Fix off-by-one error for '%M' case.
diff --git a/gcc/jump.c b/gcc/jump.c
index 978b2666a0e..121375395bd 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -420,6 +420,28 @@ jump_optimize_1 (f, cross_jump, noop_moves, after_regscan,
 
 	      if (temp2 == temp)
 		{
+		  /* Ensure that we jump to the later of the two labels.  
+		     Consider:
+
+			if (test) goto L2;
+			goto L1;
+			...
+		      L1:
+			(clobber return-reg)
+		      L2:
+			(use return-reg)
+
+		     If we leave the goto L1, we'll incorrectly leave
+		     return-reg dead for TEST true.  */
+
+		  temp2 = next_active_insn (JUMP_LABEL (insn));
+		  if (!temp2)
+		    temp2 = get_last_insn ();
+		  if (GET_CODE (temp2) != CODE_LABEL)
+		    temp2 = prev_label (temp2);
+		  if (temp2 != JUMP_LABEL (temp))
+		    redirect_jump (temp, temp2, 1);
+
 		  delete_jump (insn);
 		  changed = 1;
 		  continue;