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Subject: Re: [PATCH v3 06/15] arm: Fix mve_vmvnq_n_<supf><mode> argument mode
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To: Christophe Lyon <christophe.lyon@foss.st.com>, gcc-patches@gcc.gnu.org,
 Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>, richard.sandiford@arm.com
References: <20220113145645.4077141-1-christophe.lyon@foss.st.com>
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 <c2c7a5ea-9a2b-f5ec-c8c4-aef3e0a6fc71@arm.com> <mpttudyn0rh.fsf@arm.com>
From: "Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com>
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On 20/01/2022 10:45, Richard Sandiford wrote:
> "Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com> writes:
>> On 13/01/2022 14:56, Christophe Lyon via Gcc-patches wrote:
>>> The vmvnq_n* intrinsics and have [u]int[16|32]_t arguments, so use
>>> <V_elem> iterator instead of HI in mve_vmvnq_n_<supf><mode>.
>>>
>>> 2022-01-13  Christophe Lyon  <christophe.lyon@foss.st.com>
>>>
>>> 	gcc/
>>> 	* config/arm/mve.md (mve_vmvnq_n_<supf><mode>): Use V_elem mode
>>> 	for operand 1.
>>>
>>> diff --git a/gcc/config/arm/mve.md b/gcc/config/arm/mve.md
>>> index 171dd384133..5c3b34dce3a 100644
>>> --- a/gcc/config/arm/mve.md
>>> +++ b/gcc/config/arm/mve.md
>>> @@ -617,7 +617,7 @@ (define_insn "mve_vcvtaq_<supf><mode>"
>>>    (define_insn "mve_vmvnq_n_<supf><mode>"
>>>      [
>>>       (set (match_operand:MVE_5 0 "s_register_operand" "=w")
>>> -	(unspec:MVE_5 [(match_operand:HI 1 "immediate_operand" "i")]
>>> +	(unspec:MVE_5 [(match_operand:<V_elem> 1 "immediate_operand" "i")]
>>>    	 VMVNQ_N))
>>>      ]
>>>      "TARGET_HAVE_MVE"
>> While fixing this it might be good to fix the constraint and predicate
>> inspired by "DL" and "neon_inv_logic_op2" respectively. This would avoid
>> the compiler generating wrong assembly, and instead it would probably
>> lead to the compiler using a load literal.
> FWIW: for cases like this, I think it's better to define a predicate
> only (not a constraint).  By design, the only time that constraints
> are used independently of predicates is during RA, and there's nothing
> that RA can/should do for immediate operands.
>
> Thanks,
> Richard
Yeah, if I use a predicate it doesn't like the fact that we are passing 
an argument 'imm' rather than actual immediate. To use a constraint like 
DL I'd also need to change the builtin to take a vector of immediates, 
since we can't use immediates as they don't have a mode and the 
constraint needs to be able to know what mode we are using.

This will have to wait...