diff options
Diffstat (limited to 'arch/cris/arch-v10/lib/memset.c')
| -rw-r--r-- | arch/cris/arch-v10/lib/memset.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/arch/cris/arch-v10/lib/memset.c b/arch/cris/arch-v10/lib/memset.c new file mode 100644 index 0000000..82bb668 --- /dev/null +++ b/arch/cris/arch-v10/lib/memset.c @@ -0,0 +1,252 @@ +/*#************************************************************************#*/ +/*#-------------------------------------------------------------------------*/ +/*# */ +/*# FUNCTION NAME: memset() */ +/*# */ +/*# PARAMETERS: void* dst; Destination address. */ +/*# int c; Value of byte to write. */ +/*# int len; Number of bytes to write. */ +/*# */ +/*# RETURNS: dst. */ +/*# */ +/*# DESCRIPTION: Sets the memory dst of length len bytes to c, as standard. */ +/*# Framework taken from memcpy. This routine is */ +/*# very sensitive to compiler changes in register allocation. */ +/*# Should really be rewritten to avoid this problem. */ +/*# */ +/*#-------------------------------------------------------------------------*/ +/*# */ +/*# HISTORY */ +/*# */ +/*# DATE NAME CHANGES */ +/*# ---- ---- ------- */ +/*# 990713 HP Tired of watching this function (or */ +/*# really, the nonoptimized generic */ +/*# implementation) take up 90% of simulator */ +/*# output. Measurements needed. */ +/*# */ +/*#-------------------------------------------------------------------------*/ + +#include <linux/types.h> + +/* No, there's no macro saying 12*4, since it is "hard" to get it into + the asm in a good way. Thus better to expose the problem everywhere. + */ + +/* Assuming 1 cycle per dword written or read (ok, not really true), and + one per instruction, then 43+3*(n/48-1) <= 24+24*(n/48-1) + so n >= 45.7; n >= 0.9; we win on the first full 48-byte block to set. */ + +#define ZERO_BLOCK_SIZE (1*12*4) + +void *memset(void *pdst, + int c, + size_t plen) +{ + /* Ok. Now we want the parameters put in special registers. + Make sure the compiler is able to make something useful of this. */ + + register char *return_dst __asm__ ("r10") = pdst; + register int n __asm__ ("r12") = plen; + register int lc __asm__ ("r11") = c; + + /* Most apps use memset sanely. Only those memsetting about 3..4 + bytes or less get penalized compared to the generic implementation + - and that's not really sane use. */ + + /* Ugh. This is fragile at best. Check with newer GCC releases, if + they compile cascaded "x |= x << 8" sanely! */ + __asm__("movu.b %0,$r13\n\t" + "lslq 8,$r13\n\t" + "move.b %0,$r13\n\t" + "move.d $r13,%0\n\t" + "lslq 16,$r13\n\t" + "or.d $r13,%0" + : "=r" (lc) : "0" (lc) : "r13"); + + { + register char *dst __asm__ ("r13") = pdst; + + /* This is NONPORTABLE, but since this whole routine is */ + /* grossly nonportable that doesn't matter. */ + + if (((unsigned long) pdst & 3) != 0 + /* Oops! n=0 must be a legal call, regardless of alignment. */ + && n >= 3) + { + if ((unsigned long)dst & 1) + { + *dst = (char) lc; + n--; + dst++; + } + + if ((unsigned long)dst & 2) + { + *(short *)dst = lc; + n -= 2; + dst += 2; + } + } + + /* Now the fun part. For the threshold value of this, check the equation + above. */ + /* Decide which copying method to use. */ + if (n >= ZERO_BLOCK_SIZE) + { + /* For large copies we use 'movem' */ + + /* It is not optimal to tell the compiler about clobbering any + registers; that will move the saving/restoring of those registers + to the function prologue/epilogue, and make non-movem sizes + suboptimal. + + This method is not foolproof; it assumes that the "asm reg" + declarations at the beginning of the function really are used + here (beware: they may be moved to temporary registers). + This way, we do not have to save/move the registers around into + temporaries; we can safely use them straight away. + + If you want to check that the allocation was right; then + check the equalities in the first comment. It should say + "r13=r13, r12=r12, r11=r11" */ + __asm__ volatile (" + ;; Check that the following is true (same register names on + ;; both sides of equal sign, as in r8=r8): + ;; %0=r13, %1=r12, %4=r11 + ;; + ;; Save the registers we'll clobber in the movem process + ;; on the stack. Don't mention them to gcc, it will only be + ;; upset. + subq 11*4,$sp + movem $r10,[$sp] + + move.d $r11,$r0 + move.d $r11,$r1 + move.d $r11,$r2 + move.d $r11,$r3 + move.d $r11,$r4 + move.d $r11,$r5 + move.d $r11,$r6 + move.d $r11,$r7 + move.d $r11,$r8 + move.d $r11,$r9 + move.d $r11,$r10 + + ;; Now we've got this: + ;; r13 - dst + ;; r12 - n + + ;; Update n for the first loop + subq 12*4,$r12 +0: + subq 12*4,$r12 + bge 0b + movem $r11,[$r13+] + + addq 12*4,$r12 ;; compensate for last loop underflowing n + + ;; Restore registers from stack + movem [$sp+],$r10" + + /* Outputs */ : "=r" (dst), "=r" (n) + /* Inputs */ : "0" (dst), "1" (n), "r" (lc)); + + } + + /* Either we directly starts copying, using dword copying + in a loop, or we copy as much as possible with 'movem' + and then the last block (<44 bytes) is copied here. + This will work since 'movem' will have updated src,dst,n. */ + + while ( n >= 16 ) + { + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + n -= 16; + } + + /* A switch() is definitely the fastest although it takes a LOT of code. + * Particularly if you inline code this. + */ + switch (n) + { + case 0: + break; + case 1: + *(char*)dst = (char) lc; + break; + case 2: + *(short*)dst = (short) lc; + break; + case 3: + *((short*)dst)++ = (short) lc; + *(char*)dst = (char) lc; + break; + case 4: + *((long*)dst)++ = lc; + break; + case 5: + *((long*)dst)++ = lc; + *(char*)dst = (char) lc; + break; + case 6: + *((long*)dst)++ = lc; + *(short*)dst = (short) lc; + break; + case 7: + *((long*)dst)++ = lc; + *((short*)dst)++ = (short) lc; + *(char*)dst = (char) lc; + break; + case 8: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + break; + case 9: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *(char*)dst = (char) lc; + break; + case 10: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *(short*)dst = (short) lc; + break; + case 11: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((short*)dst)++ = (short) lc; + *(char*)dst = (char) lc; + break; + case 12: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + break; + case 13: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *(char*)dst = (char) lc; + break; + case 14: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *(short*)dst = (short) lc; + break; + case 15: + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((long*)dst)++ = lc; + *((short*)dst)++ = (short) lc; + *(char*)dst = (char) lc; + break; + } + } + + return return_dst; /* destination pointer. */ +} /* memset() */ |
