gcc/

	* recog.c (split_insn): Consider attaching a REG_EQUAL note to the
	final insn of a split.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@139802 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5a2ec12..b6186bb 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2008-08-30  Richard Sandiford  <rdsandiford@googlemail.com>
+
+       * recog.c (split_insn): Consider attaching a REG_EQUAL note to the
+       final insn of a split.
+
 2008-08-30  Jan Hubicka  <jh@suse.cz>
 
        * postreload-gcse.c (gate_handle_gcse2): Disable for functions

diff --git a/gcc/recog.c b/gcc/recog.c
index 44d3b40..8da4e20 100644 (file)
--- a/gcc/recog.c
+++ b/gcc/recog.c
@@ -2630,10 +2630,29 @@ split_insn (rtx insn)
   /* Split insns here to get max fine-grain parallelism.  */
   rtx first = PREV_INSN (insn);
   rtx last = try_split (PATTERN (insn), insn, 1);
+  rtx insn_set, last_set, note;
 
   if (last == insn)
     return NULL_RTX;
 
+  /* If the original instruction was a single set that was known to be
+     equivalent to a constant, see if we can say the same about the last
+     instruction in the split sequence.  The two instructions must set
+     the same destination.  */
+  insn_set = single_set (insn);
+  if (insn_set)
+    {
+      last_set = single_set (last);
+      if (last_set && rtx_equal_p (SET_DEST (last_set), SET_DEST (insn_set)))
+       {
+         note = find_reg_equal_equiv_note (insn);
+         if (note && CONSTANT_P (XEXP (note, 0)))
+           set_unique_reg_note (last, REG_EQUAL, XEXP (note, 0));
+         else if (CONSTANT_P (SET_SRC (insn_set)))
+           set_unique_reg_note (last, REG_EQUAL, SET_SRC (insn_set));
+       }
+    }
+
   /* try_split returns the NOTE that INSN became.  */
   SET_INSN_DELETED (insn);
 
@@ -2651,6 +2670,7 @@ split_insn (rtx insn)
          first = NEXT_INSN (first);
        }
     }
+
   return last;
 }