From: Simon Horman <horms@xxxxxxxxxx> Date: Sun, 9 Feb 2025 11:07:25 +0000 > 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. I thought they might help people in future. I can remove them if you insist. BTW the original patch from Jose also added several variants. Thanks, Olek
