After some off-line exchanges with Dave Korn, it seems to me that part of the problem is that the documentation for -funsafe-math-optimizations is so vague as to have no discernable meaning.
For example, does the wording of the documentation convey the limitation that one should only invoke math functions with a small range of arguments (say, -pi to +pi)? I cannot see anything remotely resembling that limitation, but others can. Given that, I wonder how we can tell whether a particular proposed optimization governed by that flag is permissible. Consider: `-funsafe-math-optimizations' Allow optimizations for floating-point arithmetic that (a) assume that arguments and results are valid and (b) may violate IEEE or ANSI standards. What does (b) mean? What if anything are its limitations? Is returning 1.2e27 as the result for a sin() call authorized by (b)? I would not have expected that, but I can't defend that expectation based on a literal reading of the text... paul