llvm dev - Feb 2015 - [LLVMdev] CPUStringIsValid() into MCSubtargetInfo and use it for ARM .cpu parsing

Tim,
       How about the below option ?

1. Specify an existing generic armv7 CPU or the CPU which is close my custom
variant. My custom variant can be treated as "cortex-a9" + hwdiv.
    So my CPU here is "cortex-a9"
2. Specify the ".arch_extension idiv" which is available as an
extension for my custom variant.
3. Teach LLVM & Clang about your CPU's features, either locally or
upstream.
4. Pass "-mhwdiv=arm,thumb" to Clang (or less if you only have hwdiv
in one mode).

--Sumanth G
-----Original Message-----
From: Tim Northover [mailto:t.p.northover at gmail.com] 
Sent: Tuesday, January 27, 2015 6:44 PM
To: Sumanth Gundapaneni
Cc: LLVM Developers Mailing List; Roman Divacky; Ana Pazos
Subject: Re: [LLVMdev] CPUStringIsValid() into MCSubtargetInfo and use it for
ARM .cpu parsing

Hi Sumanth,
> Shouldn’t the eabi attributes be honored ?
EABI attributes are instructions for the linker on which object files are
compatible with each other, not instructions for the assembler (and trying to
make them so sounds like a recipe for confusion to me).
>From the ARM ABI addenda:
"Build attributes record data that a linker needs to reason mechanically
about the compatibility, or incompatibility, of a set of relocatable
files."
> What should be the approach to fix the issue which I am facing?
There are a few options here:
1. Specify an existing CPU that has hardware division (notably,
Cortex-A9 doesn't).
2. Teach LLVM & Clang about your CPU's features, either locally or
upstream.
3. Pass "-mhwdiv=arm,thumb" to Clang (or less if you only have hwdiv
in one mode).

Cheers.

Tim.

> How about the below option ?
My options were mutually exclusive, or at least any one of them would
allow you to assemble code using sdiv/udiv. You probably don't need to
combine them.
> 1. Specify an existing generic armv7 CPU or the CPU which is close my
custom variant. My custom variant can be treated as "cortex-a9" +
hwdiv. So my CPU here is "cortex-a9"
> 2. Specify the ".arch_extension idiv" which is available as an
extension for my custom variant.
This looks like it'd be sufficient (and I didn't know about
.arch_extension at all, or I'd have mentioned it. Thanks!).
> 3. Teach LLVM & Clang about your CPU's features, either locally or
upstream.
> 4. Pass "-mhwdiv=arm,thumb" to Clang (or less if you only have
hwdiv in one mode).
These ought to be unneeded if you do 1+2 above.

Cheers.

Tim.

On 29 January 2015 at 03:36, Tim Northover <t.p.northover at gmail.com>
wrote:
> These ought to be unneeded if you do 1+2 above.
As far as I remember, .arch_extension does change the assembler flags
to support whatever you set. Have you tried that?

cheers,
--renato

I have pushed the patch here: http://reviews.llvm.org/D7316
Review it and let me know.

--Sumanth G
> I have tried ".arch_extension" and it works perfectly fine for
me.
> I will move ahead and add the arch_extension framework to ARM.
>
> Thanks for your guidance guys.
> --Sumanth G
> -----Original Message-----
> From: Renato Golin [mailto:renato.golin at linaro.org]
> Sent: Thursday, January 29, 2015 9:03 AM
> To: Tim Northover
> Cc: Sumanth Gundapaneni; Roman Divacky; LLVM Developers Mailing List
> Subject: Re: [LLVMdev] CPUStringIsValid() into MCSubtargetInfo and use it
> for ARM .cpu parsing
>
> On 29 January 2015 at 03:36, Tim Northover <t.p.northover at
gmail.com>
> wrote:
>> These ought to be unneeded if you do 1+2 above.
>
> As far as I remember, .arch_extension does change the assembler flags to
> support whatever you set. Have you tried that?
>
> cheers,
> --renato
>

Renato agreed to the patch.
Patch http://reviews.llvm.org/D7316
Waiting for an "approved" bit.
It has been there for three days idle.
> I have pushed the patch here: http://reviews.llvm.org/D7316
> Review it and let me know.
>
> --Sumanth G
>> I have tried ".arch_extension" and it works perfectly fine
for me.
>> I will move ahead and add the arch_extension framework to ARM.
>>
>> Thanks for your guidance guys.
>> --Sumanth G
>> -----Original Message-----
>> From: Renato Golin [mailto:renato.golin at linaro.org]
>> Sent: Thursday, January 29, 2015 9:03 AM
>> To: Tim Northover
>> Cc: Sumanth Gundapaneni; Roman Divacky; LLVM Developers Mailing List
>> Subject: Re: [LLVMdev] CPUStringIsValid() into MCSubtargetInfo and use
>> it
>> for ARM .cpu parsing
>>
>> On 29 January 2015 at 03:36, Tim Northover <t.p.northover at
gmail.com>
>> wrote:
>>> These ought to be unneeded if you do 1+2 above.
>>
>> As far as I remember, .arch_extension does change the assembler flags
to
>> support whatever you set. Have you tried that?
>>
>> cheers,
>> --renato
>>
>
>
>