llvm dev - Jul 2012 - [LLVMdev] RFC: Staging area proposal for new backends

On Fri, Jul 27, 2012 at 10:54:21PM -0400, Justin Holewinski
wrote:
> On Jul 27, 2012, at 7:05 PM, Chris Lattner <clattner at apple.com>
wrote:
> 
> > On Jul 27, 2012, at 1:39 PM, Tom Stellard wrote:
> >> 
> >>> We also need to come up with a plan regarding cutting
releases. When
> >>> 3.2 is branched, will all "staged" back-ends be
removed?  Or will
> >>> they be left in the distribution so interested parties can
build
> >>> them?
> >>> 
> >> 
> >> I can't really think of any disadvantages to keeping staged
backends
> >> in releases.  Being in a release would help a backend get more
exposure
> >> and increase the number of users/testers it would get.
> > 
> > I agree, there is no reason to remove it from the source drop of the
release.  The binaries produced for each release shouldn't include them
though.
> 
> Sounds good to me, I agree that more exposure is best.
> 
> In terms of build system integration, I think it makes sense to do the
following:
> 
> Add a ENABLE_EXPERIMENTAL or ENABLE_STAGING flag that allows experimental
features to be built (default: OFF)
> Add an LLVM_STAGING_TARGETS list that contains all of the staging back-ends
> Allow LLVM_TARGETS_TO_BUILD to contain a back-end from LLVM_STAGING_TARGETS
*only* if ENABLE_STAGING is ON
>
> This will allow the default configuration to not only skip the staging
back-ends, but prohibit them from being built without explicitly setting
ENABLE_STAGING.  Further, this will allow picking-and-choosing which staging
back-ends to build.
Hi,

I've submitted a patch[1] that adds this option.

[1]
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120730/147282.html
> 
> Is there any reason not to try this out with the R600 target?
> 
> > 
> > -Chris
> > 
>

On 30 Jul 2012, at 19:18, Tom Stellard wrote:
> On Fri, Jul 27, 2012 at 10:54:21PM -0400, Justin Holewinski wrote:
>> Add a ENABLE_EXPERIMENTAL or ENABLE_STAGING flag that allows
experimental features to be built (default: OFF)
>> Add an LLVM_STAGING_TARGETS list that contains all of the staging
back-ends
>> Allow LLVM_TARGETS_TO_BUILD to contain a back-end from
LLVM_STAGING_TARGETS *only* if ENABLE_STAGING is ON
> 
> I've submitted a patch[1] that adds this option.
> 
> [1]
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120730/147282.html

Could we perhaps call these LLVM_ENABLE_EXPERIMENTAL and
LLVM_EXPERIMENTAL_TARGETS, instead of STAGING?  I don't know how clear the
meaning of "staging" will be to someone who hasn't been following
this discussion. (Someone who isn't a compiler guru might wonder whether
"staging" has some special meaning in the field of compilers.)

The only places that "staging" is currently mentioned in the LLVM
sources are:

* the comments in lib/MC/WinCOFFObjectWriter.cpp, which mention "staging
data for a COFF relocation entry".

* the comments in utils/llvm-compilers-check, where "staging" means
something slightly different from this proposal.

Cheers,
Dave.

On Tue, Jul 31, 2012 at 07:22:02AM +0100, David Röthlisberger
wrote:
> On 30 Jul 2012, at 19:18, Tom Stellard wrote:
> > On Fri, Jul 27, 2012 at 10:54:21PM -0400, Justin Holewinski wrote:
> >> Add a ENABLE_EXPERIMENTAL or ENABLE_STAGING flag that allows
experimental features to be built (default: OFF)
> >> Add an LLVM_STAGING_TARGETS list that contains all of the staging
back-ends
> >> Allow LLVM_TARGETS_TO_BUILD to contain a back-end from
LLVM_STAGING_TARGETS *only* if ENABLE_STAGING is ON
> > 
> > I've submitted a patch[1] that adds this option.
> > 
> > [1]
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120730/147282.html
> 
> 
> Could we perhaps call these LLVM_ENABLE_EXPERIMENTAL and
LLVM_EXPERIMENTAL_TARGETS, instead of STAGING?  I don't know how clear the
meaning of "staging" will be to someone who hasn't been following
this discussion. (Someone who isn't a compiler guru might wonder whether
"staging" has some special meaning in the field of compilers.)
>
I think this makes sense.  I'll update the patches.

-Tom
> The only places that "staging" is currently mentioned in the LLVM
sources are:
> 
> * the comments in lib/MC/WinCOFFObjectWriter.cpp, which mention
"staging data for a COFF relocation entry".
> 
> * the comments in utils/llvm-compilers-check, where "staging"
means something slightly different from this proposal.
> 
> Cheers,
> Dave.
> 
>

On 07/31/2012 02:22 AM, David Röthlisberger wrote:
> On 30 Jul 2012, at 19:18, Tom Stellard wrote:
>> On Fri, Jul 27, 2012 at 10:54:21PM -0400, Justin Holewinski wrote:
>>> Add a ENABLE_EXPERIMENTAL or ENABLE_STAGING flag that allows
experimental features to be built (default: OFF)
>>> Add an LLVM_STAGING_TARGETS list that contains all of the staging
back-ends
>>> Allow LLVM_TARGETS_TO_BUILD to contain a back-end from
LLVM_STAGING_TARGETS *only* if ENABLE_STAGING is ON
>> I've submitted a patch[1] that adds this option.
>>
>> [1]
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120730/147282.html
>
> Could we perhaps call these LLVM_ENABLE_EXPERIMENTAL and
LLVM_EXPERIMENTAL_TARGETS, instead of STAGING?  I don't know how clear the
meaning of "staging" will be to someone who hasn't been following
this discussion. (Someone who isn't a compiler guru might wonder whether
"staging" has some special meaning in the field of compilers.)
>
> The only places that "staging" is currently mentioned in the LLVM
sources are:
>
> * the comments in lib/MC/WinCOFFObjectWriter.cpp, which mention
"staging data for a COFF relocation entry".
>
> * the comments in utils/llvm-compilers-check, where "staging"
means something slightly different from this proposal.
That's a fair point.  I'm okay with calling them EXPERIMENTAL instead of
STAGED.
>
> Cheers,
> Dave.
>
-- 
Thanks,

Justin Holewinski