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FW: [PATCH GCC/pr56124] Don't prefer memory if the source of load operation has side effect
- From: "Bin Cheng" <bin dot cheng at arm dot com>
- To: <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 25 Mar 2013 15:15:09 +0800
- Subject: FW: [PATCH GCC/pr56124] Don't prefer memory if the source of load operation has side effect
Sorry for the wrong list.
-----Original Message-----
From: Bin Cheng [mailto:bin.cheng@arm.com]
Sent: Monday, March 25, 2013 3:00 PM
To: gcc@gcc.gnu.org
Subject: [PATCH GCC/pr56124] Don't prefer memory if the source of load
operation has side effect
Hi,
As reported in PR56124, IRA causes redundant reload by preferring to put
pseudo which is target of loading in memory. Generally this is good but the
case in which the src of loading has side effect.
This patch fixes this issue by checking whether source of loading has side
effect.
I tested the patch on x86/thumb2. Is it OK? Thanks.
2013-03-25 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.
Index: gcc/ira-costs.c
===================================================================
--- gcc/ira-costs.c (revision 197029)
+++ gcc/ira-costs.c (working copy)
@@ -1293,10 +1293,13 @@ 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))