[LLVMdev] Question about ARM/vfp/NEON code generation

[Jan-Simon Möller]

Am Samstag, 28. Mai 2011, 11:38:38 schrieb Renato Golin:
> On 27 May 2011 19:47, Jim Grosbach <grosbach at apple.com> wrote:
> > Not exactly. The distinction is clear, it's just not expressed as an
> > either/or question. Specifically, the code generator considers NEON to be
> > a proper superset of VFP3. So if it has only VFP3, that's all it will
> > use. If it has NEON, it assumes it also has VFP3 and can use either.
> 
> Indeed.
> 
> > There's not,
> > currently, a way to say "use only NEON instructions; don't generate any
> > VFP3."
> 
> Which would be advantageous on some cases, where NEON instructions are
> faster than VFP3.
> 
> But the way it's done today in LLVM is correct. The output doesn't
> have to be different between NEON and VFP3 for VFP3 operations, but it
> can be. GCC has some of that knowledge and it's just a matter of time
> for LLVM to catch up. ;)
> 

Just out of curiosity: do we output vfpv3-d16 or -d32 (e.g. d16= tegra2, dove) 
?  Or doesn't it apply for LLVM (currently) ?

Best,
Jan-Simon