On Wed, May 25, 2016 at 03:34:55AM -0400, George Spelvin wrote:
+static inline u32 __attribute_const__ __hash_32(u32 x)
+{
+ u32 a, b;
+
+ asm( "move.l %2,%0" /* 0x0001 */
+ "\n lsl.l #2,%0" /* 0x0004 */
+ "\n move.l %0,%1"
+ "\n lsl.l #7,%0" /* 0x0200 */
+ "\n add.l %2,%0" /* 0x0201 */
+ "\n add.l %0,%1" /* 0x0205 */
+ "\n add.l %0,%0" /* 0x0402 */
+ "\n add.l %0,%1" /* 0x0607 */
+ "\n lsl.l #5,%0" /* 0x8040 */
+ /* 0x8647 */
There is no standard way to write asm in the kernel, but I prefer
a simple semicolon after each insn
asm("move.l %2,%0;" /* 0x0001 */
"lsl.l #2,%0;" /* 0x0004 */
"move.l %0,%1;"
"lsl.l #7,%0;" /* 0x0200 */
"add.l %2,%0;" /* 0x0201 */
"add.l %0,%1;" /* 0x0205 */
"add.l %0,%0;" /* 0x0402 */
"add.l %0,%1;" /* 0x0607 */
"lsl.l #5,%0" /* 0x8040 */
/* 0x8647 */
Also, it took me some time to understand the hexadecimal constants
in the comments (and the last one predicts a future event :)).
+ : "=&d" (a), "=&r" (b)
+ : "g" (x));
+
+ return ((u16)(x*0x61c8) << 16) + a + b;
+}
Just my two cents
Philippe
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