optabs.c (add_equal_note): Do not create self-referencing REG_EQUAL notes.

	* optabs.c (add_equal_note): Do not create self-referencing REG_EQUAL
	notes.
	* fwprop.c (forward_propagate_and_simplify): Likewise.

From-SVN: r194054

gcc/ChangeLog

 2012-12-02  Steven Bosscher  <steven@gcc.gnu.org>
 
+	* optabs.c (add_equal_note): Do not create self-referencing REG_EQUAL
+	notes.
+	* fwprop.c (forward_propagate_and_simplify): Likewise.
+
+2012-12-02  Steven Bosscher  <steven@gcc.gnu.org>
+
 	* function.h (struct rtl_data): Remove epilogue_delay_list.
 	* reorg.c (find_end_label): Simplify always-true test.
 	(optimize_skip): Likewise.

gcc/fwprop.c

@@ -1315,9 +1315,12 @@ forward_propagate_and_simplify (df_ref use, rtx def_insn, rtx def_set)
       /* Do not replace an existing REG_EQUAL note if the insn is not
 	 recognized.  Either we're already replacing in the note, or we'll
 	 separately try plugging the definition in the note and simplifying.
-	 And only install a REQ_EQUAL note when the destination is a REG,
-	 as the note would be invalid otherwise.  */
-      set_reg_equal = (note == NULL_RTX && REG_P (SET_DEST (use_set)));
+	 And only install a REQ_EQUAL note when the destination is a REG
+	 that isn't mentioned in USE_SET, as the note would be invalid
+	 otherwise.  */
+      set_reg_equal = (note == NULL_RTX && REG_P (SET_DEST (use_set))
+		       && ! reg_mentioned_p (SET_DEST (use_set),
+					     SET_SRC (use_set)));
     }
 
   if (GET_MODE (*loc) == VOIDmode)

gcc/optabs.c

@@ -170,14 +170,14 @@ optab_libfunc (optab optab, enum machine_mode mode)
 
    If the last insn does not set TARGET, don't do anything, but return 1.
 
-   If a previous insn sets TARGET and TARGET is one of OP0 or OP1,
-   don't add the REG_EQUAL note but return 0.  Our caller can then try
-   again, ensuring that TARGET is not one of the operands.  */
+   If the last insn or a previous insn sets TARGET and TARGET is one of OP0
+   or OP1, don't add the REG_EQUAL note but return 0.  Our caller can then
+   try again, ensuring that TARGET is not one of the operands.  */
 
 static int
 add_equal_note (rtx insns, rtx target, enum rtx_code code, rtx op0, rtx op1)
 {
-  rtx last_insn, insn, set;
+  rtx last_insn, set;
   rtx note;
 
   gcc_assert (insns && INSN_P (insns) && NEXT_INSN (insns));
@@ -192,6 +192,12 @@ add_equal_note (rtx insns, rtx target, enum rtx_code code, rtx op0, rtx op1)
   if (GET_CODE (target) == ZERO_EXTRACT)
     return 1;
 
+  /* If TARGET is in OP0 or OP1, punt.  We'd end up with a note referencing
+     a value changing in the insn, so the note would be invalid for CSE.  */
+  if (reg_overlap_mentioned_p (target, op0)
+      || (op1 && reg_overlap_mentioned_p (target, op1)))
+    return 0;
+
   for (last_insn = insns;
        NEXT_INSN (last_insn) != NULL_RTX;
        last_insn = NEXT_INSN (last_insn))
@@ -207,21 +213,6 @@ add_equal_note (rtx insns, rtx target, enum rtx_code code, rtx op0, rtx op1)
 	  || ! rtx_equal_p (XEXP (SET_DEST (set), 0), target)))
     return 1;
 
-  /* If TARGET is in OP0 or OP1, check if anything in SEQ sets TARGET
-     besides the last insn.  */
-  if (reg_overlap_mentioned_p (target, op0)
-      || (op1 && reg_overlap_mentioned_p (target, op1)))
-    {
-      insn = PREV_INSN (last_insn);
-      while (insn != NULL_RTX)
-	{
-	  if (reg_set_p (target, insn))
-	    return 0;
-
-	  insn = PREV_INSN (insn);
-	}
-    }
-
   if (GET_RTX_CLASS (code) == RTX_UNARY)
     switch (code)
       {