[llvm-commits] [llvm] r150060 - in /llvm/trunk: include/llvm/IntrinsicsX86.td lib/Target/X86/X86ISelLowering.cpp lib/Target/X86/X86InstrSSE.td

[Duncan Sands]

Hi Dave,

>> I didn't try, but turning __builtin_ia32_vpermilpd into an inline asm is
>> presumably rather trivial.
>
> I don't know how hard it would be.  The frontend would have to know
> about mnemonics, at least.  And it would have to know whether to
> generate AT&T or Intel syntax.

I'm not sure this is true any more.  The LLVM code generators nowadays parse
inline asm and can output it either as object code or in AT&T or Intel syntax.
At least I think they can.  If so, the syntax issue has gone away.

Ciao, Duncan.

   It strikes me as the wrong place to do
> this when the mechanisms already exist in the current codegen.
>
>> But why not give it a go?
>
> Because it works now, we've been using it for years and I have a million
> other things to fix and improve.
>
> Could it be done?  Sure.  Is it worth the expense to do it given an
> existing solution?  No way.
>
>>> What is so difficult about keeping intrinsics around?  Are they causing
>>> some major issue?
>>
>> I'm not the one removing intrinsics, and I don't know what the reason is.
>> However keeping useless functionality does create a maintenance burden for
>> no real benefit.
>
> They're not useless.  We are using them.  And I question whether it is
> much of a maintenance burden at all.  Who goes and changes existing
> intrinsics?
>
>> I call these intrinsics useless since you can get the same
>> semantic effect using generic IR
>
> Users expect more than the same semantic effect.
>
>> or exactly the instruction using inline asm.
>
> With a lot of extra work which is completely unnecessary given that a
> solution already exists.
>
>> If turning them into inline asm is a real pain as you suspect, then I
>> for one would vote to keep the intrinsics.
>
> It is infinitely more painful than just using what we already have, what
> we know works and which requires zero effort to keep working.
>
>                            -Dave