[PATCH] D19015: [LTO] ensure lto_codegen_debug_options() are passed on to LLVM

[Mehdi Amini via llvm-commits]

> On Apr 13, 2016, at 10:14 AM, Robinson, Paul <Paul_Robinson at playstation.sony.com> wrote:
> 
> 
> 
>> -----Original Message-----
>> From: Rafael Espíndola [mailto:rafael.espindola at gmail.com]
>> Sent: Wednesday, April 13, 2016 8:43 AM
>> To: reviews+D19015+public+3b72f3e9e30a204c at reviews.llvm.org
>> Cc: Guest, Thomas (SCEE); Peter Collingbourne; Robinson, Paul; llvm-
>> commits; Tim Amini Golling
>> Subject: Re: [PATCH] D19015: [LTO] ensure lto_codegen_debug_options() are
>> passed on to LLVM
>> 
>> On 13 April 2016 at 11:38, Thomas Guest <thomas_guest at sn.scee.net> wrote:
>>> thomasguest added a comment.
>>> 
>>> In http://reviews.llvm.org/D19015#399821, @probinson wrote:
>>> 
>>>> Let me point out that the gold plugin works exactly this way (pass in
>> cl options as a string).
>>>> It might not be ideal but it's what we have today.
>>>> LLVM-as-library doesn't really have another way to conjure up
>> TargetOptions (I *think* clang creates one directly, sorry can't check
>> right now, but that seems even more fragile).
>>> 
>>> 
>>> Thanks for the information @probinson
>>> I was imagining the way to configure codegen via the C API would be to
>> add a new function: lto_codegen_configure(lto_codegen_t cg, char ** argv,
>> int argc);
>> 
>> No, you should not expose argv for anything other than debug.
>> 
>> As it was pointed out, if you want to programmatically  set an option,
>> you should do something like what clang does.
> 
> What clang does is instantiate llvm::TargetOptions and fill in the fields
> directly.  That is a *bad API* because it too closely ties the caller and
> callee to lock-step revisions.  Clang statically links LLVM so there is
> no versioning problem, but it is definitely not the right library API.

I'd argue that this is the ok as an API for LTOCodeGenerator (C++ API, tightly coupled, no stability), not for the C API of libLTO.dylib. Are we OK on this distinction?

-- 
Mehdi


> --paulr
> 
>> 
>> Cheers,
>> Rafael