[backport from gcc-4.7/trunk r184310, fixes missed-optimization
 regression PR52208 from PR37273 patch <mikpe@it.uu.se>]

gcc/

2012-02-16  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/52208
	* ira-costs.c (scan_one_insn): Don't decrease mem_cost
	for MEMs with REG_EQUIV, if the MEM isn't general_operand.

--- gcc-4.6.3/gcc/ira-costs.c.~1~	2012-03-10 14:17:41.000000000 +0100
+++ gcc-4.6.3/gcc/ira-costs.c	2012-03-10 14:21:51.000000000 +0100
@@ -1029,13 +1029,20 @@ scan_one_insn (rtx insn)
 
      Similarly if we're loading other constants from memory (constant
      pool, TOC references, small data areas, etc) and this is the only
-     assignment to the destination pseudo.  */
+     assignment to the destination pseudo.
+
+     Don't do this if SET_SRC (set) isn't a general operand, if it is
+     a memory requiring special instructions to load it, decreasing
+     mem_cost might result in it being loaded using the specialized
+     instruction into a register, then stored into stack and loaded
+     again from the stack.  See PR52208.  */
   if (set != 0 && REG_P (SET_DEST (set)) && MEM_P (SET_SRC (set))
       && (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != NULL_RTX
       && ((MEM_P (XEXP (note, 0)))
 	  || (CONSTANT_P (XEXP (note, 0))
 	      && LEGITIMATE_CONSTANT_P (XEXP (note, 0))
-	      && REG_N_SETS (REGNO (SET_DEST (set))) == 1)))
+	      && REG_N_SETS (REGNO (SET_DEST (set))) == 1))
+      && general_operand (SET_SRC (set), GET_MODE (SET_SRC (set))))
     {
       enum reg_class cl = GENERAL_REGS;
       rtx reg = SET_DEST (set);