On Tue, 16 Oct 2012 10:49:34 +0530, Arun Raghavan <arun.raghavan at collabora.co.uk> wrote: > 3. How shall we go about enabling this code? Have a configure time check > for some instructions that are needed, build it in if available, and > then run-time detection should pick the right code path? GCC does not support the target function attribute on ARM, so NEON cannot be enabled selectively, on a per function basis. As a consequence, intrinsics and inline assembler cannot be used for run-time-conditional NEON code: the code will only compile if NEON is enabled in CFLAGS. Yet if NEON is enabled in CFLAGS, the compiler may emit NEON instruction for plain C code such that the code will not run at all on processors without NEON. So .S/.s assembler source files constitute the only way to write run-time-conditional NEON code for the time being. Just make sure you did _not_ enable NEON in the CFLAGS and enable it manually with the ".fpu neon" assembler directive. Personally, I much prefer .S/.s file over inline asm because I find them more readable, but it's a matter of taste. -- R?mi Denis-Courmont Sent from my collocated server
