[RFC] Patch to keep CSE from removing a necessary load

["Pranav Bhandarkar" <pranav.bhandarkar@gmail.com>]

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Hi,
Subsequent to the following discussion

http://gcc.gnu.org/ml/gcc/2007-07/msg00878.html

I have the following patch. It gave no regressions with the GCC
testsuite on my port ( private port) and a proprietary testsuite.

Thanks,
Pranav

ChangeLog
        * lower-subreg.c (remove_retval_note): Remove REG_EQUAL note too
        if it exists in an insn containing REG_RETVAL note.

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Index: lower-subreg.c
===================================================================
--- lower-subreg.c      (revision 127059)
+++ lower-subreg.c      (working copy)
@@ -586,9 +586,10 @@
 static void
 remove_retval_note (rtx insn1)
 {
-  rtx note0, insn0, note1, insn;
+  rtx note0, insn0, note1, note2, insn;

   note1 = find_reg_note (insn1, REG_RETVAL, NULL);
+  note2 = find_reg_note (insn1, REG_EQUAL, NULL);
   if (note1 == NULL_RTX)
     return;

@@ -598,6 +599,9 @@
   remove_note (insn0, note0);
   remove_note (insn1, note1);

+  if (note2)
+    remove_note (insn1, note2);
+
   for (insn = insn0; insn != insn1; insn = NEXT_INSN (insn))
     {
       while (1)