[llvm-dev] [cfe-dev] Just a quick heads up -- removing BBVectorize from LLVM (and Clang)

C Bergström via llvm-dev llvm-dev at lists.llvm.org
Fri Jun 30 19:01:13 PDT 2017

I don't know how others feel, but it seems this was removed more by feeling
and less by actual data points. It doesn't mean it wasn't the correct
choice, but just because nobody spoke up could mean that they silently
enjoy the benefits and maybe some end user far away isn't subscribed. With
this in mind - I hope others would consider turning optimizations into an
Assert, Warning or Error if they will be removed - at least for a release.
That way there's some visible warning that users had a chance to see and
potentially relay the feedback. The middle ground could be disabling the
transformation and just warning on the analysis pass. "Foo optimization has
been removed and it may impact your code performance"...

Too much work?

On Sat, Jul 1, 2017 at 9:32 AM, Chandler Carruth via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Already added in the commit (I think)
> On Fri, Jun 30, 2017 at 3:58 PM Hans Wennborg <hans at chromium.org> wrote:
>> On Thu, Jun 29, 2017 at 3:42 PM, Chandler Carruth via cfe-dev
>> <cfe-dev at lists.llvm.org> wrote:
>> > If you don't use BBVectorize at all, you can ignore this.
>> >
>> > Hal suggested this in a thread in 2014:
>> > http://lists.llvm.org/pipermail/llvm-dev/2014-November/079091.html
>> >
>> > None objected then, and I don't think any new uses have arisen so I
>> plan to
>> > just remove it. It is causing maintenance burden, complexity, and is a
>> set
>> > of features I'd rather not port to the new PM.
>> >
>> > Just an FYI email to folks so they aren't confused when the patches
>> land.
>> Maybe worth mentioning in the release notes?
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