Denormal input handling

[Michael Morrell]

I see support in QEMU for architectures which have a denormal input flag bit 
and those that have a "flush inputs to zero" control bit, but the 
implementation is not specializable and seems wrong for x86 at least.

For example, in sf_canonicalize, if the input is denormal and 
"flush_inputs_to_zero" is true, the "input denormal" flag is set and then the 
value is set to a zero value, and if the input is denormal and 
"flush_inputs_to_zero" is false, then the input is simply normalized.

I think the behavior should be for denormal inputs that if 
"flush_inputs_to_zero" is true, then set the value to zero (without setting the 
"input denormal" flag); and if "flush_inputs_to_zero" is false, set the "input 
denormal" flag and normalize the input.

This matches what x86 does (I'm not sure about other architectures).

Am I missing something?  If not, I can work on a patch (there are several 
places which check "flush_inputs_to_zero" which will need to be changed).

  Michael