Skip to contentSkip to conversation

Calculate log base 2 in radeon.h based on clz for all platforms

PATCH In review Jochen Rollwagen 2 participants 2 messages Dec 2, 2016 – Dec 5, 2016 1 message not in the archive

lore
Share & tools
lore

Jochen Rollwagen

author
#0 lore raw

PATCH 1/1 Calculate log base 2 in radeon.h based on clz for all platforms

This commit replaces the inline assembler code (for x86 platforms) and loop (for non-x86 platforms) in RADEONLog2 with a one-liner version based on clz (count leading zeroes).

---
 src/radeon.h |   13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)
src/radeon.h +1 -12
index 5797bed..23ecfeb 100644
@@ -935,18 +935,7 @@ enum {
 static __inline__ int
 RADEONLog2(int val)
 {
-    int bits;
-#if (defined __i386__ || defined __x86_64__) && (defined __GNUC__)
-    __asm volatile("bsrl    %1, %0"
-        : "=r" (bits)
-        : "c" (val)
-    );
-    return bits;
-#else
-    for (bits = 0; val != 0; val >>= 1, ++bits)
-        ;
-    return bits - 1;
-#endif
+    return (31 - __builtin_clz(val));
 }
 
 #define RADEON_TILING_MASK                0xff
Signature · 1 line
1.7.9.5
Quoted 1 line

From 350d663a5ce85d51632a6fa56d28afa2447c6558 Mon Sep 17 00:00:00 2001

From: Jochen Rollwagen <[email protected]>
Date: Fri, 2 Dec 2016 10:56:39 +0100
Subject: [PATCH] Calculate log base 2 in radeon.h based on clz for all
platforms

This commit replaces the inline assembler code (for x86 platforms) and loop (for non-x86 platforms) in RADEONLog2 with a one-liner version based on clz (count leading zeroes).

---
 src/radeon.h |   13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)
src/radeon.h +1 -12
index 5797bed..23ecfeb 100644
@@ -935,18 +935,7 @@ enum {
 static __inline__ int
 RADEONLog2(int val)
 {
-	int bits;
-#if (defined __i386__ || defined __x86_64__) && (defined __GNUC__)
-	__asm volatile("bsrl	%1, %0"
-		: "=r" (bits)
-		: "c" (val)
-	);
-	return bits;
-#else
-	for (bits = 0; val != 0; val >>= 1, ++bits)
-		;
-	return bits - 1;
-#endif
+	return (31 - __builtin_clz(val));
 }
 
 #define RADEON_TILING_MASK				0xff
Signature · 1 line
1.7.9.5

_______________________________________________
amd-gfx mailing list
[email protected]
https://lists.freedesktop.org/mailman/listinfo/amd-gfx

A message that is not in the archive (sent off-list or not yet received): [email protected]

#2 lore raw
Quoted 21 lines · Jochen Rollwagen

This commit replaces the inline assembler code (for x86 platforms) and loop (for non-x86 platforms) in RADEONLog2 with a one-liner version based on clz (count leading zeroes).

---
 src/radeon.h |   13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)
src/radeon.h +0 -6
index 5797bed..23ecfeb 100644
@@ -935,18 +935,7 @@ enum {
 static __inline__ int
 RADEONLog2(int val)
 {
-    int bits;
-#if (defined __i386__ || defined __x86_64__) && (defined __GNUC__)
-    __asm volatile("bsrl    %1, %0"
-        : "=r" (bits)
-        : "c" (val)
-    );

src/radeon.h enum { · line 941

Quoted 10 lines
src/radeon.h +1 -6
-    return bits;
-#else
-    for (bits = 0; val != 0; val >>= 1, ++bits)
-        ;
-    return bits - 1;
-#endif
+    return (31 - __builtin_clz(val));
 }
 
 #define RADEON_TILING_MASK                0xff

Reviewed and pushed (with the superfluous parentheses removed and the commit log line-wrapped at ~72 columns), thanks!

One request for future patches you want to be applied: Please put your
Signed-off-by: tag in the commit log.

Signature · 6 lines
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
_______________________________________________
amd-gfx mailing list
[email protected]
https://lists.freedesktop.org/mailman/listinfo/amd-gfx