linux-kernel - [PATCH 2/2] infiniband: Use unsigned for bit index

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Date:	Fri, 16 Jan 2015 15:39:56 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] infiniband: Use unsigned for bit index

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@...musvillemoes.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

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