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Re: [PATCH IRA] update_equiv_regs fails to set EQUIV reg-note for pseudo with more than one definition
- From: Felix Yang <fei dot yang0953 at gmail dot com>
- To: "Yangfei (Felix)" <felix dot yang at huawei dot com>
- Cc: Jeff Law <law at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, "vmakarov at redhat dot com" <vmakarov at redhat dot com>
- Date: Tue, 23 Sep 2014 18:45:55 +0800
- Subject: Re: [PATCH IRA] update_equiv_regs fails to set EQUIV reg-note for pseudo with more than one definition
- Authentication-results: sourceware.org; auth=none
- References: <CAFc0fxz3Fdr9rgLscjTzZm0PoBn53y028tQU4=U0BXQ0kY6+KA at mail dot gmail dot com> <54206D2C dot 708 at redhat dot com> <DA41BE1DDCA941489001C7FBD7A8820E55542982 at szxema507-mbx dot china dot huawei dot com>
Hi,
Attached please fined the updated patch.
Cheers,
Felix
On Tue, Sep 23, 2014 at 10:48 AM, Yangfei (Felix) <felix.yang@huawei.com> wrote:
>> On 09/22/14 08:40, Felix Yang wrote:
>> > Hi,
>> >
>> > I find that update_equiv_regs in ira.c sets the wrong EQUIV
>> > reg-note for pseudo with more than one definiton in certain situation.
>> > Here is a simplified RTL snippet after this function finishs handling:
>> >
>> > (insn 77 37 78 2 (set (reg:SI 171)
>> > (const_int 0 [0])) ticket151.c:33 52 {movsi_internal_dsp}
>> > (expr_list:REG_EQUAL (const_int 0 [0])
>> > (nil)))
>> >
>> > ......
>> >
>> > (insn 79 50 53 2 (set (mem/c:SI (reg/f:SI 136) [2 g_728+0 S4 A64])
>> > (reg:SI 171)) ticket151.c:33 52 {movsi_internal_dsp}
>> > (expr_list:REG_DEAD (reg:SI 171)
>> > (nil)))
>> > (insn 53 79 54 2 (set (mem/c:SI (reg/f:SI 162) [4 g_163+0 S4 A32])
>> > (reg:SI 163)) 52 {movsi_internal_dsp}
>> > (expr_list:REG_DEAD (reg:SI 163)
>> > (expr_list:REG_DEAD (reg/f:SI 162)
>> > (nil))))
>> > (insn 54 53 14 2 (set (reg:SI 171)
>> > (mem/u/c:SI (symbol_ref/u:SI ("*.LC8") [flags 0x2]) [4 S4
>> > A32])) ticket151.c:49 52 {movsi_internal_dsp}
>> > (expr_list:REG_EQUIV (mem/u/c:SI (symbol_ref/u:SI ("*.LC8")
>> > [flags 0x2]) [4 S4 A32])
>> > (expr_list:REG_EQUAL (mem/u/c:SI (symbol_ref/u:SI ("*.LC8")
>> > [flags 0x2]) [4 S4 A32])
>> > (nil))))
>> >
>> >
>> > The REG_EQUIV of insn 54 is not correct as pseudo 171 is defined
>> > in insn 77 with a differerent value.
>> > This may causes reload replacing pseudo 171 with mem/u/c:SI
>> > (symbol_ref/u:SI ("*.LC8"), which is wrong.
>> > A proposed patch for this issue, please comment:
>> Is it possible it's the conditional just above this one that is incorrect?
>>
>> if (DF_REG_DEF_COUNT (regno) != 1
>> && (! note
>> || rtx_varies_p (XEXP (note, 0), 0)
>> || (reg_equiv[regno].replacement
>> && ! rtx_equal_p (XEXP (note, 0),
>>
>> reg_equiv[regno].replacement))))
>> {
>> no_equiv (dest, set, NULL);
>> continue;
>> }
>>
>>
>> ISTM the only time a multiply-set register can have a valid REG_EQUIV note is if
>> each and every assignment to that pseudo has the same RHS.
>>
>> Jeff
>
>
> Thanks Jeff. Yes, I agree that this is a better place to consider. I am thinking of a better way to fix this.
>
> Vladimir, can you shed light on this and give me some suggestions? Thank you.
>