re PR rtl-optimization/56124 (Redundant reload for loading from memory)

	PR target/56124
	* ira-costs.c (scan_one_insn): Check whether the source rtx of
	loading has side effect.

From-SVN: r197691

gcc/ChangeLog

+2013-04-11  Bin Cheng  <bin.cheng@arm.com>
+
+	PR target/56124
+	* ira-costs.c (scan_one_insn): Check whether the source rtx of
+	loading has side effect.
+
 2013-04-10  Steven Bosscher  <steven@gcc.gnu.org>
 
 	* config/sparc/sparc.c: Include tree-pass.h.

gcc/ira-costs.c

@@ -1292,10 +1292,13 @@ scan_one_insn (rtx insn)
      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.  */
+     again from the stack.  See PR52208.
+     
+     Don't do this if SET_SRC (set) has side effect.  See PR56124.  */
   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)))
+      && ((MEM_P (XEXP (note, 0))
+	   && !side_effects_p (SET_SRC (set)))
 	  || (CONSTANT_P (XEXP (note, 0))
 	      && targetm.legitimate_constant_p (GET_MODE (SET_DEST (set)),
 						XEXP (note, 0))