-mfpmath=387 flag does not prevent gcc from using SSE/SSE2 instructions

[Jan Hubicka]

> > I thought the behaviour would be not to generate any SSE/SSE2 instruction with 
> > this flag. Am I wrong, or could this be a (small) bug?
> 
> The x86-64 ABI requires passing floating pointer arguments
> in SSE registers. Disabling it is not possible, you would
> be incompatible to all libraries.

Additionally -mfpmath=i387 will still use SSE for scalar floating point
operations where the results are known to be equivalent to the 387
counterparts (ie the extra precisity of 80/bit 387 registers does not
matter, such as for negation, moves, some conversions and comparsions).

Honza
> 
> -Andi