[PATCH] D14071: [FPEnv Core 06/14] Do not fold constants on reading in IR asm/bitcode

[Sergey Dmitrouk via llvm-commits]

sdmitrouk added a comment.

In http://reviews.llvm.org/D14071#275275, @majnemer wrote:

> That sounds like an oversight.  We have overflow flags (`nsw`/`nuw`) for integer math.


Actually I asked about this last year, but it appeared that there is not much use of fast-math flags for constant expressions.
See it on the list <http://lists.llvm.org/pipermail/llvm-dev/2014-December/079242.html>.

> I am not, I am thinking about the general case.  It sounds reasonable to transform floating-point divide by zero into SNaN when fp-exceptions are enabled.


As it can yield infinity, I'm not sure whether SNaN is a good replacement for it. It would nice to do not fold anything in some case, maybe when both flags are given, not sure if "exceptions" or "rounding" is good choice on their own.


Repository:
  rL LLVM

http://reviews.llvm.org/D14071