---

yaml --- r: 277454 b: refs/heads/master c: 668b448 h: refs/heads/master v: v3
git-mirror · Dec 5, 2011 · f7f4811 · f7f4811
1 parent c88391e
commit f7f4811
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Showing 2 changed files with 15 additions and 9 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f6b2bc847641ea38e2655c8424fef5d2d19f35f9
+refs/heads/master: 668b44846606185a9bed5a5357bc2cb132e00dd7
diff --git a/trunk/arch/x86/include/asm/div64.h b/trunk/arch/x86/include/asm/div64.h
@@ -4,6 +4,7 @@
 #ifdef CONFIG_X86_32
 
 #include <linux/types.h>
+#include <linux/log2.h>
 
 /*
  * do_div() is NOT a C function. It wants to return
@@ -21,15 +22,20 @@
 ({								\
 	unsigned long __upper, __low, __high, __mod, __base;	\
 	__base = (base);					\
-	asm("":"=a" (__low), "=d" (__high) : "A" (n));		\
-	__upper = __high;					\
-	if (__high) {						\
-		__upper = __high % (__base);			\
-		__high = __high / (__base);			\
+	if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \
+		__mod = n & (__base - 1);			\
+		n >>= ilog2(__base);				\
+	} else {						\
+		asm("" : "=a" (__low), "=d" (__high) : "A" (n));\
+		__upper = __high;				\
+		if (__high) {					\
+			__upper = __high % (__base);		\
+			__high = __high / (__base);		\
+		}						\
+		asm("divl %2" : "=a" (__low), "=d" (__mod)	\
+			: "rm" (__base), "0" (__low), "1" (__upper));	\
+		asm("" : "=A" (n) : "a" (__low), "d" (__high));	\
 	}							\
-	asm("divl %2":"=a" (__low), "=d" (__mod)		\
-	    : "rm" (__base), "0" (__low), "1" (__upper));	\
-	asm("":"=A" (n) : "a" (__low), "d" (__high));		\
 	__mod;							\
 })