[llvm-dev] what is official way to determine if we are running lto 2nd stage?

[Mehdi Amini via llvm-dev]

> On Sep 12, 2016, at 10:01 PM, Konstantin Vladimirov <konstantin.vladimirov at gmail.com> wrote:
> 
> Hi,
> 
> Imagine that your backend has valid asm instruction written like this:
> 
> "%x mnem %y, %z"
> 
> And user puts it as inline assembler:
> 
> __asm__ ("%x mnem %y, %z");
> 
> It can not be parsed with current llvm asm parser, because it starts
> with % (moreover it has mnemonic in second place)
> 
> Say you written pass, that makes it "mnem %x, %y, %z".
> 
> Now this guy can be parsed, but can not be encoded by gas. You simply
> havent that instruction in you assembler. For LTO it isn't a problem:
> you can make arbitrary MCInst from everything that comes into
> ParseInstruction. But it is problem for regular scenario where wrong
> asm will be printed and then passed to gas.
> 
> So I want to apply this on 2nd lto stage where AsmParser is inevitable
> and to not apply in non-LTO cases.

OK, from what you are describing, it does not seem a LTO vs non-LTO, but integrated-ASM vs non-integrated-ASM, right?

— 
Mehdi



> 
> ---
> With best regards, Konstantin
> 
> On Mon, Sep 12, 2016 at 10:19 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:
>> 
>>> On Sep 12, 2016, at 11:07 AM, Konstantin Vladimirov <konstantin.vladimirov at gmail.com> wrote:
>>> 
>>> Hi,
>>> 
>>> This is really basic block level pass. It is no difference what is
>>> level, problem is the same.
>> 
>> Can you clarify what you mean? If you have a MachineFunction pass, it’ll run in the backend only.
>> I don’t understand why you would need to distinguish between LTO or no-LTO here.
>> 
>>> 
>>> After fixing for asm parser, assembler syntax is no more valid for
>>> backend, without processing with asm parser.
>> 
>> My understanding of Inline ASM is that it is supposed to be opaque to the backend till you reach MC.
>> So I don’t understand this sentence "no more valid for backend, without processing with asm parser”.
>> 
>> Sorry if my answers don’t make sense to you, I may still be missing a key part of your problem.
>> 
>> —
>> Mehdi
>> 
>> 
>>> May be it will be solution to process inline asm on insn printer level
>>> to remove syntax fixes. But just switch it off without lto will make
>>> compiler do less job
>>> 
>>> P.S. sorry for dup, maillist CC lost on first sent.
>>> 
>>> ---
>>> WIth best regards, Konstantin
>>> 
>>> 
>>> On Mon, Sep 12, 2016 at 8:52 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:
>>>> 
>>>>> On Sep 12, 2016, at 9:26 AM, Konstantin Vladimirov <konstantin.vladimirov at gmail.com> wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> In LTO we have AsmParser that process inline assembler instructions to
>>>>> MCInst and I want to fix some inline assembler in order to conform its
>>>>> rules (do not start with non-identifier and so on) because asm syntax
>>>>> of our backend allows some incompatible patterns. In order to do this
>>>>> I am adding IR-level target-specific pass. But those fixes shall not
>>>>> be applied when there is no AsmParser later to process them. So I want
>>>>> to switch this pass off if we are not in 2nd lto stage.
>>>> 
>>>> This is not clear to me: how should this be different for LTO than for a non-LTO compile?
>>>> 
>>>> Also, if you’re only fixing the inline ASM, why doing it as an IR-level pass instead of MachineFunctionPass?
>>>> 
>>>> —
>>>> Mehdi
>>>> 
>>>> 
>>>>> 
>>>>> I think, I can make target-specific option and make user to supply it
>>>>> whenever he wants to run 2nd lto stage, but this is ugly.
>>>>> 
>>>>> Can I somehow ask, say, about whole string of options and then parse
>>>>> it to match "lto" from here?
>>>>> 
>>>>> ---
>>>>> With best regards, Konstantin
>>>>> 
>>>>> On Mon, Sep 12, 2016 at 6:17 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:
>>>>>> Hi,
>>>>>> 
>>>>>> 
>>>>>>> On Sep 12, 2016, at 1:26 AM, Konstantin Vladimirov via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>>>>>> 
>>>>>>> Hi,
>>>>>>> 
>>>>>>> I want to enable some target-specific functionality only if current
>>>>>>> build is 2nd LTO stage (i.e. optimizer called from plugin). What is
>>>>>>> best and recommended way to do it?
>>>>>> 
>>>>>> There is none. We can setup a different optimizer pass pipeline for LTO, but the target specific part (i.e. the backend) isn’t supposed to behave differently.
>>>>>> 
>>>>>> This is an issue in general with LTO where options from the command line (like -fno-builtins, or -fveclib=xxxx) are not correctly propagated to LTO.
>>>>>> 
>>>>>> What kind of behavior do you want to enable exactly?
>>>>>> 
>>>>>> —
>>>>>> Mehdi
>>>>>> 
>>>> 
>>