PATCH: fix clang to emit correct addrspacecast for CUDA

[Justin Holewinski]

The hard part would be making this optimization general enough to be 
target-independent.  Optimizing to non-zero address spaces may not make 
sense for all targets (or even all future versions of PTX).  I agree 
that there should be an IR-level optimization for this, but perhaps its 
too target-specific and should actually live in the back-end.

On 03/24/2014 01:05 PM, Jingyue Wu wrote:
> Right. We are aware of this issue, and think it should be addressed in 
> the IR optimizer (similar to InstCombineLoadCast and 
> InstCombineStoreToCast) instead of clang. Do you think this is an 
> appropriate approach? Is this optimization general enough to stay in 
> the IR optimizer or target-dependent?
>
> Jingyue
>
>
> On Mon, Mar 24, 2014 at 4:54 AM, Justin Holewinski 
> <justin.holewinski at gmail.com <mailto:justin.holewinski at gmail.com>> wrote:
>
>     Hi Jingyue,
>
>     I committed the addrspacecast isel patterns to NVPTX.  Also, I
>     wanted to point out that your changes in the last test case in
>     this patch (address-spaces.cu <http://address-spaces.cu>)
>     represent changes that may lead to performance degradation.
>      Specific address spaces should be used whenever possible for
>     loads/stores.  Casting everything to a generic address is still
>     correct, but may lead to additional indirections for the hardware.
>
>
>     On Fri, Mar 21, 2014 at 2:25 PM, Justin Holewinski
>     <jholewinski at nvidia.com <mailto:jholewinski at nvidia.com>> wrote:
>
>         addrspacecast support in NVPTX is on my todo list.  I'll try
>         to put something together in the next few days.
>
>
>         On 3/21/14, 2:20 PM, Jingyue Wu wrote:
>>         Hi,
>>
>>         Static local variables in CUDA can be declared with address
>>         space qualifiers, such as __shared__. Therefore, the codegen
>>         needs to potentially addrspacecast a static local variable to
>>         the type expected by its declaration. Peter did something
>>         similar for global variables in r157167.
>>
>>         All clang tests passed.
>>
>>         Justin: The NVPTX backend support for addrspacecast seems not
>>         complete. We can send you follow-up patches once this one
>>         gets in.
>>
>>         Jingyue
>
>
>         -- 
>         Thanks,
>
>         Justin Holewinski
>
>         ------------------------------------------------------------------------
>         This email message is for the sole use of the intended
>         recipient(s) and may contain confidential information.  Any
>         unauthorized review, use, disclosure or distribution is
>         prohibited.  If you are not the intended recipient, please
>         contact the sender by reply email and destroy all copies of
>         the original message.
>         ------------------------------------------------------------------------
>
>
>
>
>     -- 
>
>     Thanks,
>
>     Justin Holewinski
>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20140324/0b413a7a/attachment.html>