[llvm-dev] PlaceSafepoints, operand bundles, and RewriteStatepointsForGC

[Pat Gavlin via llvm-dev]

> LLILC should mostly Just Work in
this new world, with the exception of gc transition operands -- the
LLILC frontend will have to denote these using "gc-transition" operand
bundles, and not by eagerly emitting gc.statepoint calls.  You should
be able to test out your changes by passing in -spp-no-statepoints
and -rs4gc-use-deopt-bundles to the LLVM build used in LLILC.

Thanks for the heads up. Seems straightforward enough to me.

> Please let me know once you're okay with me making the switch to
-spp-no-statepoints and -rs4gc-use-deopt-bundles being clamped to
true.

IMO you can go ahead and make this change. We may be broken
against ToT for a few days, but AFAIK that shouldn't block other
work in progress. Joe, feel free to correct me if I'm wrong :)

- Pat
________________________________________
From: Sanjoy Das <sanjoy at playingwithpointers.com>
Sent: Wednesday, January 27, 2016 9:01 AM
To: llvm-dev; Joseph Tremoulet; Pat Gavlin; Swaroop Sridhar; Andy Ayers; Russell Hadley; Philip Reames; Manuel Jacob
Subject: PlaceSafepoints, operand bundles, and RewriteStatepointsForGC

[+CC llvm-dev this time]

Hi,

As discussed in the review thread in https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2freviews.llvm.org%2fD16439%2c&data=01%7c01%7cpagavlin%40microsoft.com%7cf1cf46adca2b4e1b89dd08d3273b9d79%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=7aNJfJqykAmhImChq5Ww%2fiQWFEqZZCEYtPglbMCuqbc%3d
the future plan around statepoints, deopt bundles, PlaceSafepoints
etc. is to "constant fold" -spp-no-statepoints
and -rs4gc-use-deopt-bundles to true.

We (Azul) have moved to a representation of safepoint polls, deopt
state etc. that enables us to do the above; and at this point I'm
waiting for an okay from you guys.  LLILC should mostly Just Work in
this new world, with the exception of gc transition operands -- the
LLILC frontend will have to denote these using "gc-transition" operand
bundles, and not by eagerly emitting gc.statepoint calls.  You should
be able to test out your changes by passing in -spp-no-statepoints
and -rs4gc-use-deopt-bundles to the LLVM build used in LLILC.

Please let me know once you're okay with me making the switch to
-spp-no-statepoints and -rs4gc-use-deopt-bundles being clamped to
true.

-- Sanjoy