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From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Roland Dreier <roland@kernel.org>,
	Sean Hefty <sean.hefty@intel.com>,
	Hal Rosenstock <hal.rosenstock@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] infiniband: Use unsigned for bit index
Date: Fri, 16 Jan 2015 15:39:56 +0100	[thread overview]
Message-ID: <1421419196-4659-2-git-send-email-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <1421419196-4659-1-git-send-email-linux@rasmusvillemoes.dk>

In the expressions idx/32 and idx%32, both idx and 32 have signed
type, and unfortunately the C standard prescribes rounding to 0, so
unless gcc can prove that idx is non-negative, these cannot be
implemented as simple shift respectively mask operations. Help gcc by
changing the type of idx to unsigned - this cuts another few
instructions from the generated code.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/infiniband/hw/ocrdma/ocrdma_verbs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c b/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c
index eff11e6c6183..61c3047f5170 100644
--- a/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c
+++ b/drivers/infiniband/hw/ocrdma/ocrdma_verbs.c
@@ -1479,10 +1479,10 @@ mbx_err:
 	return status;
 }
 
-static void ocrdma_srq_toggle_bit(struct ocrdma_srq *srq, int idx)
+static void ocrdma_srq_toggle_bit(struct ocrdma_srq *srq, unsigned int idx)
 {
-	int i = idx / 32;
-	unsigned int mask = (1 << (idx % 32));
+	unsigned int i = idx / 32;
+	u32 mask = (1U << (idx % 32));
 
 	srq->idx_bit_fields[i] ^= mask;
 }
-- 
2.1.3

  reply	other threads:[~2015-01-16 14:39 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-16 14:39 [PATCH 1/2] infiniband: Help gcc generate better code for ocrdma_srq_toggle_bit Rasmus Villemoes
2015-01-16 14:39 ` Rasmus Villemoes [this message]
     [not found]   ` <1421419196-4659-2-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-02 12:03     ` [PATCH 2/2] infiniband: Use unsigned for bit index Selvin Xavier
     [not found] ` <1421419196-4659-1-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-01-30 23:00   ` [PATCH 1/2] infiniband: Help gcc generate better code for ocrdma_srq_toggle_bit Rasmus Villemoes
     [not found]     ` <87twz7ho25.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-01-31 11:07       ` Yann Droneaud
     [not found]         ` <1422702466.3030.4.camel-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org>
2015-02-02 12:58           ` Selvin Xavier
2015-02-02 12:04   ` Selvin Xavier

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