[PATCH 5/9] bitfield: FIELD_MODIFY: Only do a single read/write on the target

david.laight.linux
2025-12-09T10:03:33Z

From: David Laight <david.laight.linux@gmail.com>

Replace the:
*reg &= ~mask; *reg |= new_value;
with a single assignment.
While the compiler will usually optimise the extra access away
it isn't guaranteed.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
include/linux/bitfield.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 3e013da9ea12..3e0e8533bb66 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -200,8 +200,7 @@
__auto_type _val = 1 ? (val) : _mask; \
typecheck_pointer(_reg_p); \
__BF_FIELD_CHECK(_mask, *_reg_p, _val, "FIELD_MODIFY: "); \
- *_reg_p &= ~_mask; \
- *_reg_p |= ((_val << __bf_shf(_mask)) & _mask); \
+ *_reg_p = (*_reg_p & ~_mask) | ((_val << __bf_shf(_mask)) & _mask); \
})

extern void __compiletime_error("value doesn't fit into mask")
--
2.39.5