> Hi, > > Please forgive this post but I've tried the archives & google and amunable 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 forARM 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? > I don't know, but I guess you could try compiling a testcase with a simple loop using -mfpu=vfp -mfloat-abi=softfp -ftree-vectorize -ftree-vectorizer-verbose=# and see what it says (it will report if it wasn't able to vectorize, and why). (The bare minimum to enable vectorization for the target is to define UNITS_PER_SIMD_WORD to the size in bytes of the vector registers available under TARGET_VFP in the arm port. I'm not so familiar with this port; the closest thing I see in arm/arm.h is this: /* Use the option -mvectorize-with-neon-quad to override the use of doubleword registers when autovectorizing for Neon, at least until multiple vector widths are supported properly by the middle-end. */ #define UNITS_PER_SIMD_WORD \ (TARGET_NEON ? (TARGET_NEON_VECTORIZE_QUAD ? 16 : 8) : UNITS_PER_WORD) ) dorit > 4) Is there a better place to look for this information? :-) > > > > Cheers, > > Tom > > >
