[PATCH] -fftz-math: assume that denorms _must_ be flushed to zero optimizations

[Joseph Myers]

On Mon, 14 Aug 2017, Pekka Jääskeläinen wrote:

> Both the inputs and outputs must be flushed to zero in the HSAIL’s
> ‘ftz’ semantics.

Presumably this means that constant folding needs to know about those 
semantics, both for operations with a subnormal floating-point argument 
(whether or not the output is floating point, or floating point in the 
same format), and those with such a result?

Can assignments copy subnormals without converting them to zero?  Should 
comparisons flush input subnormals to zero before comparing?  Should 
conversions e.g. from float to double convert a float subnormal input to 
zero?

-- 
Joseph S. Myers
joseph@codesourcery.com