[LLVMdev] Bug 16257 - fmul of undef ConstantExpr not folded to undef

[Owen Anderson]

> On Sep 17, 2014, at 9:45 AM, Oleg Ranevskyy <llvm.mail.list at gmail.com> wrote:
> 
> Looking through the code I found the "NoNaNs" flag accessed through an instance of the FastMathFlags class.
> (2) and (3) should probably depend on it.
> If the flag is set, (2) and (3) cannot be folded as there are no NaNs and we are not guaranteed to get an arbitrary bit pattern from fadd, right?

The fast math flags are strictly relaxations of the normal semantics.  It should always be safe to strip them, so the set of transforms possible with fast math flags should be a superset of those available without them.

—Owen
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