netdev - RE: [PATCH next 0711] minmax: minmax: Add __types_ok3() and optimise defines with 3 arguments

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Message-ID: <78f9c15ad67940fe91ac39b9c26113be@AcuMS.aculab.com>
Date: Sun, 28 Jan 2024 19:31:22 +0000
From: David Laight <David.Laight@...LAB.COM>
To: "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>, "'Linus
 Torvalds'" <torvalds@...ux-foundation.org>, 'Netdev'
	<netdev@...r.kernel.org>, "'dri-devel@...ts.freedesktop.org'"
	<dri-devel@...ts.freedesktop.org>
CC: 'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>, 'Andrew Morton'
	<akpm@...ux-foundation.org>, "'Matthew Wilcox (Oracle)'"
	<willy@...radead.org>, 'Christoph Hellwig' <hch@...radead.org>, "'Dan
 Carpenter'" <dan.carpenter@...aro.org>, 'Linus Walleij'
	<linus.walleij@...aro.org>, "'David S . Miller'" <davem@...emloft.net>,
	"'linux-btrfs@...r.kernel.org'" <linux-btrfs@...r.kernel.org>, 'Jens Axboe'
	<axboe@...nel.dk>
Subject: RE: [PATCH next 0711] minmax: minmax: Add __types_ok3() and optimise
 defines with 3 arguments

min3() and max3() were added to optimise nested min(x, min(y, z))
sequences, bit only moved where the expansion was requiested.

Add a separate implementation for 3 argument calls.
These are never required to generate constant expressiions to
remove that logic.

Signed-off-by: David Laight <david.laight@...lab.com>
---
 include/linux/minmax.h | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index 5c7fce76abe5..278a390b8a4c 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -38,6 +38,11 @@
 	((__is_ok_signed(x) && __is_ok_signed(y)) ||	\
 	 (__is_ok_unsigned(x) && __is_ok_unsigned(y)))
 
+/* Check three values for min3(), max3() and clamp() */
+#define __types_ok3(x, y, z)							\
+	((__is_ok_signed(x) && __is_ok_signed(y) && __is_ok_signed(z)) ||	\
+	 (__is_ok_unsigned(x) && __is_ok_unsigned(y) && __is_ok_unsigned(z)))
+
 #define __cmp_op_min <
 #define __cmp_op_max >
 
@@ -87,13 +92,24 @@
 #define umax(x, y)	\
 	__careful_cmp(max, __zero_extend(x), _zero_extend(y), __COUNTER__)
 
+#define __cmp_once3(op, x, y, z, uniq) ({	\
+	typeof(x) __x_##uniq = (x);		\
+	typeof(x) __y_##uniq = (y);		\
+	typeof(x) __z_##uniq = (z);		\
+	__cmp(op, __cmp(op, __x_##uniq, __y_##uniq), __z_##uniq); })
+
+#define __careful_cmp3(op, x, y, z, uniq) ({				\
+	static_assert(__types_ok3(x, y, z),				\
+		#op "3(" #x ", " #y ", " #z ") signedness error");	\
+	__cmp_once3(op, x, y, z, uniq); })
+
 /**
  * min3 - return minimum of three values
  * @x: first value
  * @y: second value
  * @z: third value
  */
-#define min3(x, y, z) min((typeof(x))min(x, y), z)
+#define min3(x, y, z) __careful_cmp3(min, x, y, z, __COUNTER__)
 
 /**
  * max3 - return maximum of three values
@@ -101,7 +117,7 @@
  * @y: second value
  * @z: third value
  */
-#define max3(x, y, z) max((typeof(x))max(x, y), z)
+#define max3(x, y, z) __careful_cmp3(max, x, y, z, __COUNTER__)
 
 /**
  * min_t - return minimum of two values, using the specified type
@@ -142,8 +158,7 @@
 	__clamp(__val_##uniq, __lo_##uniq, __hi_##uniq); })
 
 #define __careful_clamp(val, lo, hi, uniq) ({					\
-	_Static_assert(__types_ok(val, lo), "clamp() 'lo' signedness error");	\
-	_Static_assert(__types_ok(val, hi), "clamp() 'hi' signedness error");	\
+	_Static_assert(__types_ok3(val, lo, hi), "clamp() signedness error");	\
 	__clamp_once(val, lo, hi, uniq); })
 
 /**
-- 
2.17.1

-
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