How to use VFP instructions on ARM

Tom Cooksey
Tue Jan 8 07:09:00 GMT 2008


Please forgive this post but I've tried the archives & google and am unable to 
find much info on gcc & ARM's VFP instruction set. I have a few questions:

1) How is the VFP coprocessor utilised by GCC when compiling 
with -mfpu=vfp -mfloat-abi=softfp? Will GCC emit vfp instructions for doing 
regular (scalor) floating point operations? I.e. will "float a =3.14; a *= 
20.0;" be done by the coprocessor?

2) How should I use the VFP instructions in my own code? I beleive there are 
GCC macros for using SSE instructions, is there anything similar for ARM VFP? 
(A quick traul through my GCC sources say no, but I may have missed 
something.) If not, can I use inline assembly instead and are the mnemonics 
and syntax the same as described in the ARM Architecture Reference Manual?

3) Does the GCC -ftree-vectorize work with VFP?

4) Is there a better place to look for this information? :-)



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