[llvm-dev] Possible soundness issue with available_externally (split from "RFC: Add guard intrinsics")

[Sanjoy Das via llvm-dev]

On Wed, Feb 24, 2016 at 11:18 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> It might be much more challenging, but let's try. This is not an
> issue we need to fix by the end of the month, and the potential
> optimization regressions are significant. Our deductions of
> readonly/readnone/nocapture/etc. are really important for enabling
> other optimizations. Given that all of our C++ constructors, inline
> functions, etc. end up in comdat sections, this is really important.

The only optimizations I can think of that are okay are algebraic
simplifications that don't exploit no-overflow, inbounds or exact
flags and CFG simplifications like loop unswitch and loop unroll (that
don't actually change the trace that we'll see at runtime).

-- Sanjoy