linux-kernel - [PATCH v1 3/3] regmap: place foo / 8 and foo % 8 closer to each other

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Message-ID: <20241121105838.4073659-4-andriy.shevchenko@linux.intel.com>
Date: Thu, 21 Nov 2024 12:57:23 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Mark Brown <broonie@...nel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1 3/3] regmap: place foo / 8 and foo % 8 closer to each other

On x86 the compiler (gcc (Debian 14.2.0-8) 14.2.0) may generate
a better code if it sees division and modulo goes together.

  Function                          old     new   delta
  __regmap_init                    3740    3732      -8
  Total: Before=31159, After=31151, chg -0.03%

clang (Debian clang version 18.1.8) on x86_64 still shows better code

  Function                          old     new   delta
  __regmap_init                    3582    3579      -3
  Total: Before=39854, After=39851, chg -0.01%

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 drivers/base/regmap/regmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index d2944271022c..4f8ec8528e34 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -758,13 +758,13 @@ struct regmap *__regmap_init(struct device *dev,
 		map->alloc_flags = GFP_KERNEL;
 
 	map->reg_base = config->reg_base;
+	map->reg_shift = config->pad_bits % 8;
 
-	map->format.reg_bytes = BITS_TO_BYTES(config->reg_bits);
 	map->format.pad_bytes = config->pad_bits / 8;
 	map->format.reg_shift = config->reg_shift;
+	map->format.reg_bytes = BITS_TO_BYTES(config->reg_bits);
 	map->format.val_bytes = BITS_TO_BYTES(config->val_bits);
 	map->format.buf_size = BITS_TO_BYTES(config->reg_bits + config->val_bits + config->pad_bits);
-	map->reg_shift = config->pad_bits % 8;
 	if (config->reg_stride)
 		map->reg_stride = config->reg_stride;
 	else
-- 
2.43.0.rc1.1336.g36b5255a03ac