On Sun, Feb 09, 2025 at 11:07:25AM +0000, Simon Horman wrote: > On Thu, Feb 06, 2025 at 07:26:26PM +0100, Alexander Lobakin wrote: > > There are cases when we need to explicitly unroll loops. For example, > > cache operations, filling DMA descriptors on very high speeds etc. > > Add compiler-specific attribute macros to give the compiler a hint > > that we'd like to unroll a loop. > > Example usage: > > > > #define UNROLL_BATCH 8 > > > > unrolled_count(UNROLL_BATCH) > > for (u32 i = 0; i < UNROLL_BATCH; i++) > > op(priv, i); > > > > Note that sometimes the compilers won't unroll loops if they think this > > would have worse optimization and perf than without unrolling, and that > > unroll attributes are available only starting GCC 8. For older compiler > > versions, no hints/attributes will be applied. > > For better unrolling/parallelization, don't have any variables that > > interfere between iterations except for the iterator itself. > > > > Co-developed-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> # pragmas > > Signed-off-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> > > Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx> > > Signed-off-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> > > Hi Alexander, > > This patch adds four variants of the unrolled helper. But as far as I can > tell the patch-set only makes use of one of them, unrolled_count(). > > I think it would be best if this patch only added helpers that are used. That is debatable but I think I tend to agree here. If we add say 3 unused macros then nothing stops someone from coming up with a patch that deletes them because they are unused, right? > > ...
