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Re: [PATCH] ARM half-precision floating point, 3/8 (target hooks)


On Thu, 2009-04-16 at 14:13 +0000, Joseph S. Myers wrote:
> Note that in AAPCS the conversion from half-precision to 
> single-precision is part of the language-independent argument-passing 
> rules, not part of how C language types are mapped to language-independent 
> types.
> 

True, but language-dependent rules would be applied first, so if, for
example, they changed an HFmode object into a DFmode object, then the
language independent rules would never see an HFmode object.

There's an interesting issue as to whether a HFmode value passed to a
variadic routine should be converted directly to DFmode or converted
first to SFmode and then to DFmode (not much of a problem at the moment
since passing HFmode objects by value isn't allowed at the moment, and
in any case there's no rounding in this direction); but there are
potential issues with the reverse conversion because of double rounding.

R.



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