[PATCH] D64412: [Strict FP] Allow more relaxed scheduling

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally added a comment.

I'm reviewing the trap-safety issues now and have some open questions (language lawyers needed??). Let's say we have something like this:

  z = strict_fmul x, y
  c = strict_fmul a, b
  store z
  store c

And we schedule it as:

  z = strict_fmul x, y
  store z
  c = strict_fmul a, b
  store c

Now let's say the 2nd fmul traps on overflow and we have a signal handler set up to gracefully recover. The differences in scheduling could mean memory differences when the signal handler executes. That might not be okay for the very strictest conformance mode (I don't know).

Are we treating this case as undefined behavior, like the C/C++ Standards dictate?


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  rL LLVM

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https://reviews.llvm.org/D64412