[LLVMdev] adding comment

[Reed Kotler]

Okay.

I did not know about that feature. That is definitely helpful.
You can surely verify that IR has been matched or not.

It's still useful to match patterns of asm code that you know are 
emitted by fast-isel and to not
confuse that with bits from normal instruction selection processing.

Reed

On 04/22/2014 08:50 AM, Eric Christopher wrote:
> We've generally used -fast-isel-verbose and -fast-isel-abort to deal
> with a lot of the testing of fast-isel these days, but if you can show
> a compelling use case for testing where you can't write tests
> otherwise then being able to increase our test coverage via other
> means is always welcome.
>
> -eric
>
> On Tue, Apr 22, 2014 at 8:34 AM, Reed Kotler <reed.kotler at imgtec.com> wrote:
>> Nice. I suggest you submit the patch to llvm commits.
>>
>> That will make more realistic make check tests for fast-isel and make it
>> easy to see which code is emitted by fast-isel
>> and normal isel.
>>
>>
>> On 04/22/2014 03:39 AM, Daniel Sanders wrote:
>>> I tried out CommentFlag and it looks ideal for this purpose. The attached
>>> patch adds a FastISel flag and prints it in the AsmPrinter and the IR dump.
>>> You can then call MachineInstr::setAsmPrinterFlag(MachineInstr::FastISel) to
>>> set the flag.
>>>
>>> Some passes seem to be stripping the comment flags though. The one I
>>> noticed is the pseudo-instruction expansion pass:
>>>          # *** IR Dump After Machine Copy Propagation Pass ***:
>>>          # Machine code for function retfloat: Post SSA
>>>
>>>          BB#0: derived from LLVM BB %entry
>>>                  RetRA; comment-flags: FastISel
>>>
>>>          # End machine code for function retfloat.
>>>
>>>          # *** IR Dump After Post-RA pseudo instruction expansion pass ***:
>>>          # Machine code for function retfloat: Post SSA
>>>
>>>          BB#0: derived from LLVM BB %entry
>>>                  RET %RA
>>>
>>>          # End machine code for function retfloat.
>>>
>>>> -----Original Message-----
>>>> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
>>>> On Behalf Of Reed Kotler
>>>> Sent: 17 April 2014 16:30
>>>> To: LLVMdev at cs.uiuc.edu
>>>> Subject: Re: [LLVMdev] adding comment
>>>>
>>>> Maybe adding it to CommentFlag would be slightly better.
>>>>
>>>> On 04/17/2014 02:23 AM, Daniel Sanders wrote:
>>>>> Would adding a flag to MachineInstr::MIFlag do the trick? I'm thinking
>>>>> that
>>>> fast isel could ensure that a flag (e.g. MIFlag::FastISel) is added to
>>>> the
>>>> instructions it creates, then the instruction printer could optionally
>>>> emit a
>>>> comment for instructions that have this flag.
>>>>>> -----Original Message-----
>>>>>> From: llvmdev-bounces at cs.uiuc.edu
>>>>>> [mailto:llvmdev-bounces at cs.uiuc.edu]
>>>>>> On Behalf Of Reed Kotler
>>>>>> Sent: 16 April 2014 22:17
>>>>>> To: LLVMdev at cs.uiuc.edu
>>>>>> Subject: Re: [LLVMdev] adding comment
>>>>>>
>>>>>> On 04/16/2014 02:06 PM, reed kotler wrote:
>>>>>>> Is there a simple way to add a comment in the machine instructions
>>>>>>> of a basic block?
>>>>>>>
>>>>>>> Ideally something that can be used with machine instruction builder.
>>>>>>>
>>>>>>> Tia.
>>>>>>>
>>>>>>> Reed
>>>>>> In this case, I am working on the fast instruction selector for mips.
>>>>>>
>>>>>> I want to be able to tag instructions or regions of instructions that
>>>>>> are emitted by the fast instruction selector as opposed to the normal
>>>>>> mechanism.
>>>>>>
>>>>>> In fast instruction selector can always report that it cannot emit
>>>>>> instructions for some construct and then that part falls on the
>>>>>> normal mechanism; though in some cases the actual machine instructions
>>>> emitted would be the same.
>>>>>> So I want to be able to look for some kind of tag in the make check
>>>>>> tests.
>>>>>>
>>>>>> Tia.
>>>>>>
>>>>>> Reed
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