[cfe-dev] Parallelism TS implementation and feasibility of GPUexecution policies

Wed Apr 8 03:04:21 PDT 2015

Thanks

The thing is I’m actually writing those headers (because I have to). 

So builtins are not really an issue. 

My problem was

__global__

__shared__ …

Which I defined as custom attributes

And the more than painful kernel<<<32, 128>>> which I can’t handle without modifying the front end myself (and I doesn’t look easy :) )

I’ll try the -fcuda-is-device and keep you posted

thanks

From: Eli Bendersky [mailto:eliben at google.com] 
Sent: mardi 7 avril 2015 00:44
To: C Bergström
Cc: Régis Portalez; clang-dev Developers
Subject: Re: [cfe-dev] Parallelism TS implementation and feasibility of GPUexecution policies

On Mon, Apr 6, 2015 at 3:22 PM, C Bergström <cbergstrom at pathscale.com <mailto:cbergstrom at pathscale.com> > wrote:

On Tue, Apr 7, 2015 at 4:47 AM, Eli Bendersky <eliben at google.com <mailto:eliben at google.com> > wrote:
>
>
> On Mon, Apr 6, 2015 at 11:48 AM, Régis Portalez
> <regis.portalez at altimesh.com <mailto:regis.portalez at altimesh.com> > wrote:
>>
>> Hi.
>>
>> Sorry to interrupt, but I understood there is way to emit llvm ir from
>> cuda code?
>>
>
> In general, the Clang frontend (-cc1) can generate LLVM IR for the nvptx
> triples/targets, when passed -fcuda-is-device. To use this in practice,
> you'll need to supply a bunch of things in headers (definitions of builtins,
> CUDA types and such), and no such headers exist in the open yet. Clang won't
> be able to parse the NVIDIA headers as these collide with the standard C++
> headers in some ways.

The old cuda headers used to be permissively licensed. (below)

Those headers are probably sufficient to get things "rolling", but I
don't know if they are really a good start. (Not to mention you'd be
missing a runtime)

The problem is that you'd have to do 2 passes with different
(conflicting) defines. Once for host and once for device. To get
host+device to play nice together is a b*. We have this resolved in
our clang, but it's really specific to our compilation flow. A general
solution would most likely involve extensive changes to the headers or
a rewrite. :/

Yep, this (2 passes with different defines) is the path taken in our approach, and the one we're pushing in http://reviews.llvm.org/D8463

Note that, headers notwithstanding, the 2 pass compilation flow is enforced by the definition of the CUDA language, because __CUDA_ARCH__ is defined only for device code, and undefined for host code, even though these two can live in the same TU. So you *have* to compile the code twice.

Back to the headers - these will remain a problem. We're now looking at different options.

Eli

I've fought with this for the past 5 years. I'll try to help in a
general way if/where I can.

Old CUDA header license
----------
/*
 * Copyright 1993-2010 NVIDIA Corporation.  All rights reserved.
 *
 * NOTICE TO USER:
 *
 * This source code is subject to NVIDIA ownership rights under U.S. and
 * international Copyright laws.  Users and possessors of this source code
 * are hereby granted a nonexclusive, royalty-free license to use this code
 * in individual and commercial software.
 *
 * NVIDIA MAKES NO REPRESENTATION ABOUT THE SUITABILITY OF THIS SOURCE
 * CODE FOR ANY PURPOSE.  IT IS PROVIDED "AS IS" WITHOUT EXPRESS OR
 * IMPLIED WARRANTY OF ANY KIND.  NVIDIA DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOURCE CODE, INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE.
 * IN NO EVENT SHALL NVIDIA BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL,
 * OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
 * OF USE, DATA OR PROFITS,  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION,  ARISING OUT OF OR IN CONNECTION WITH THE USE
 * OR PERFORMANCE OF THIS SOURCE CODE.
 *
 * U.S. Government End Users.   This source code is a "commercial item" as
 * that term is defined at  48 C.F.R. 2.101 (OCT 1995), consisting  of
 * "commercial computer  software"  and "commercial computer software
 * documentation" as such terms are  used in 48 C.F.R. 12.212 (SEPT 1995)
 * and is provided to the U.S. Government only as a commercial end item.
 * Consistent with 48 C.F.R.12.212 and 48 C.F.R. 227.7202-1 through
 * 227.7202-4 (JUNE 1995), all U.S. Government End Users acquire the
 * source code with only those rights set forth herein.
 *
 * Any use of this source code in individual and commercial software must
 * include, in the user documentation and internal comments to the code,
 * the above Disclaimer and U.S. Government End Users Notice.
 */

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