Messages in this thread Patch in this message | | | From | Rasmus Villemoes <> | Subject | [PATCH 1/2] infiniband: Help gcc generate better code for ocrdma_srq_toggle_bit | Date | Fri, 16 Jan 2015 15:39:55 +0100 |
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gcc emits a surprising amount of code in order to flip a bit. One would think that a single instruction is enough.
$ scripts/bloat-o-meter /tmp/ocrdma_verbs.o drivers/infiniband/hw/ocrdma/ocrdma_verbs.o add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-142 (-142) function old new delta ocrdma_post_srq_recv 498 460 -38 ocrdma_poll_cq 2010 1962 -48 ocrdma_discard_cqes 495 439 -56
All three calls of ocrdma_srq_toggle_bit happen within spinlocks, so saving a few useless instructions might be worthwhile.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- drivers/infiniband/hw/ocrdma/ocrdma_verbs.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c b/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c index fb8d8c4dfbb9..eff11e6c6183 100644 --- a/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c +++ b/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c @@ -1484,10 +1484,7 @@ static void ocrdma_srq_toggle_bit(struct ocrdma_srq *srq, int idx) int i = idx / 32; unsigned int mask = (1 << (idx % 32)); - if (srq->idx_bit_fields[i] & mask) - srq->idx_bit_fields[i] &= ~mask; - else - srq->idx_bit_fields[i] |= mask; + srq->idx_bit_fields[i] ^= mask; } static int ocrdma_hwq_free_cnt(struct ocrdma_qp_hwq_info *q) -- 2.1.3
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