[PATCH] D83379: [Coroutines] Refactor sinkLifetimeStartMarkers

[JunMa via Phabricator via llvm-commits]

junparser created this revision.
junparser added reviewers: modocache, lxfind, lewissbaker.
junparser added a project: LLVM.
Herald added subscribers: llvm-commits, hiraditya.

D82314 <https://reviews.llvm.org/D82314> has implemented a method for coroutine frame reducing in sinkLifetimeStartMarkers, which sink lifetime.start marker to multiple users.  However, this may cause mismatch. Consider this :

  coroutine  A(){ 
    a; 
    lifetime.start(a);
    if (b) 
      {
        ... // do something
        co_await
        use(a);
      }
       use(a);
      lifetime.end(a);
  } 

Since both user of a do not dominate each other, we just sink lifetime.start for both of them. This may cause  buildCoroutineFrame to  keep a as local variable.  More importantly, it introduces the pattern in resume function such like:

  lifetime.start(a);
  use(a);
  lifetime.start(a);
  use(a);
  lifetime.end(a);

which cause wrong optimization in later passes.

This patch rewrite sinkLifetimeStartMarkers which only sink lifetime.start markers when all of its user are only used inside one of suspended region.

TestPlan: cppcoro, check-llvm,  https://godbolt.org/z/zVx_eB


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83379

Files:
  llvm/lib/Transforms/Coroutines/CoroFrame.cpp
  llvm/lib/Transforms/Coroutines/CoroSplit.cpp
  llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll
  llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-02.ll
  llvm/test/Transforms/Coroutines/coro-split-sink-lifetime.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D83379.276357.patch
Type: text/x-patch
Size: 12599 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200708/ced23a89/attachment.bin>