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
I did it the way I did above because it makes the gcc -S output very legible. Just like I put a space before the perands on m68k but a tab on h8300: that's what GCC does on those platforms. I started with the "\n\t" suffixes on each line like so much other kernel code, but then figured out the format above which is legible both in C source and compiler output.
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 :)).
Can you recmmend a better way to comment this? My nose is so deep in the code it's hard for me to judge.
Just my two cents
And thank you very much for them! -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
