[PATCH] D31210: [AMDGPU] Add new address space mapping

[Siu Chi Chan via Phabricator via cfe-commits]

scchan added a comment.

In https://reviews.llvm.org/D31210#706955, @yaxunl wrote:

> In https://reviews.llvm.org/D31210#706890, @kzhuravl wrote:
>
> > In https://reviews.llvm.org/D31210#706880, @rampitec wrote:
> >
> > > I'm concerned about the default address space to be 64 bit. It would move alloca into generic address space effectively making private address to be 64 bit.
> > >  This may have very undesirable performance implications, like address arithmetic can become expensive 64 bit and only be truncated at load or store.
> > >  I realize you will use addrspacecast on an alloca's value, though I'm not sure that is sufficient to mitigate performance hit.
> > >  I believe such change shall not be made without a good performance comparison with the feature enabled, provided the very likely performance issues.
> >
> >
> > Did not we want to use this: http://lists.llvm.org/pipermail/llvm-dev/2017-March/111199.html and use non-0 for our allocas?
>
>
> Our final goal is to let alloca return private pointer. The Clang changes are mostly common whether alloca returns generic pointer or private pointer. Actually to be able to test the above patch we need to get the changes in Clang done first.


The goal for this is mainly to bring the mapping closer to nvptx?


https://reviews.llvm.org/D31210