[PATCH] D110953: [coro async] Disable lifetime.start sinking for ABI::Async and ABI::Retcon

[Arnold Schwaighofer via Phabricator via llvm-commits]

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It does not handle loops correctly i.e it moves the lifetime.start
intrinsic into a loop rendering the stack object as not alive for part
of the loop.

  entry:
    %obj = alloca i8
    lifetime.start(%obj)
  
    br loop
  
  loop:
    coro.suspend()
    escape(%obj)
    cond_br %cond, label %exit, label loop
  
    br loop
  
  exit:
    lifetime.end(%obj

After sinking:

  entry:
    %obj = alloca i8
    br loop
  
  loop:
    coro.suspend()
    lifetime.start(%obj)
    escape(%obj)
    cond_br %cond, label %exit, label loop
  
    br loop
  
  exit:
    lifetime.end(%obj

rdar://83411917


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D110953

Files:
  llvm/lib/Transforms/Coroutines/CoroFrame.cpp
  llvm/test/Transforms/Coroutines/coro-async-addr-lifetime-start-bug.ll

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