LXR linux/arch/ia64/lib/memcpy

   1/*
   2 * Itanium 2-optimized version of memcpy and copy_user function
   3 *
   4 * Inputs:
   5 *      in0:    destination address
   6 *      in1:    source address
   7 *      in2:    number of bytes to copy
   8 * Output:
   9 *      for memcpy:    return dest
  10 *      for copy_user: return 0 if success,
  11 *                     or number of byte NOT copied if error occurred.
  12 *
  13 * Copyright (C) 2002 Intel Corp.
  14 * Copyright (C) 2002 Ken Chen <kenneth.w.chen@intel.com>
  15 */
  16#include <asm/asmmacro.h>
  17#include <asm/page.h>
  18
  19#define EK(y...) EX(y)
  20
  21/* McKinley specific optimization */
  22
  23#define retval          r8
  24#define saved_pfs       r31
  25#define saved_lc        r10
  26#define saved_pr        r11
  27#define saved_in0       r14
  28#define saved_in1       r15
  29#define saved_in2       r16
  30
  31#define src0            r2
  32#define src1            r3
  33#define dst0            r17
  34#define dst1            r18
  35#define cnt             r9
  36
  37/* r19-r30 are temp for each code section */
  38#define PREFETCH_DIST   8
  39#define src_pre_mem     r19
  40#define dst_pre_mem     r20
  41#define src_pre_l2      r21
  42#define dst_pre_l2      r22
  43#define t1              r23
  44#define t2              r24
  45#define t3              r25
  46#define t4              r26
  47#define t5              t1      // alias!
  48#define t6              t2      // alias!
  49#define t7              t3      // alias!
  50#define n8              r27
  51#define t9              t5      // alias!
  52#define t10             t4      // alias!
  53#define t11             t7      // alias!
  54#define t12             t6      // alias!
  55#define t14             t10     // alias!
  56#define t13             r28
  57#define t15             r29
  58#define tmp             r30
  59
  60/* defines for long_copy block */
  61#define A       0
  62#define B       (PREFETCH_DIST)
  63#define C       (B + PREFETCH_DIST)
  64#define D       (C + 1)
  65#define N       (D + 1)
  66#define Nrot    ((N + 7) & ~7)
  67
  68/* alias */
  69#define in0             r32
  70#define in1             r33
  71#define in2             r34
  72
  73GLOBAL_ENTRY(memcpy)
  74        and     r28=0x7,in0
  75        and     r29=0x7,in1
  76        mov     f6=f0
  77        mov     retval=in0
  78        br.cond.sptk .common_code
  79        ;;
  80END(memcpy)
  81GLOBAL_ENTRY(__copy_user)
  82        .prologue
  83// check dest alignment
  84        and     r28=0x7,in0
  85        and     r29=0x7,in1
  86        mov     f6=f1
  87        mov     saved_in0=in0   // save dest pointer
  88        mov     saved_in1=in1   // save src pointer
  89        mov     retval=r0       // initialize return value
  90        ;;
  91.common_code:
  92        cmp.gt  p15,p0=8,in2    // check for small size
  93        cmp.ne  p13,p0=0,r28    // check dest alignment
  94        cmp.ne  p14,p0=0,r29    // check src alignment
  95        add     src0=0,in1
  96        sub     r30=8,r28       // for .align_dest
  97        mov     saved_in2=in2   // save len
  98        ;;
  99        add     dst0=0,in0
 100        add     dst1=1,in0      // dest odd index
 101        cmp.le  p6,p0 = 1,r30   // for .align_dest
 102(p15)   br.cond.dpnt .memcpy_short
 103(p13)   br.cond.dpnt .align_dest
 104(p14)   br.cond.dpnt .unaligned_src
 105        ;;
 106
 107// both dest and src are aligned on 8-byte boundary
 108.aligned_src:
 109        .save ar.pfs, saved_pfs
 110        alloc   saved_pfs=ar.pfs,3,Nrot-3,0,Nrot
 111        .save pr, saved_pr
 112        mov     saved_pr=pr
 113
 114        shr.u   cnt=in2,7       // this much cache line
 115        ;;
 116        cmp.lt  p6,p0=2*PREFETCH_DIST,cnt
 117        cmp.lt  p7,p8=1,cnt
 118        .save ar.lc, saved_lc
 119        mov     saved_lc=ar.lc
 120        .body
 121        add     cnt=-1,cnt
 122        add     src_pre_mem=0,in1       // prefetch src pointer
 123        add     dst_pre_mem=0,in0       // prefetch dest pointer
 124        ;;
 125(p7)    mov     ar.lc=cnt       // prefetch count
 126(p8)    mov     ar.lc=r0
 127(p6)    br.cond.dpnt .long_copy
 128        ;;
 129
 130.prefetch:
 131        lfetch.fault      [src_pre_mem], 128
 132        lfetch.fault.excl [dst_pre_mem], 128
 133        br.cloop.dptk.few .prefetch
 134        ;;
 135
 136.medium_copy:
 137        and     tmp=31,in2      // copy length after iteration
 138        shr.u   r29=in2,5       // number of 32-byte iteration
 139        add     dst1=8,dst0     // 2nd dest pointer
 140        ;;
 141        add     cnt=-1,r29      // ctop iteration adjustment
 142        cmp.eq  p10,p0=r29,r0   // do we really need to loop?
 143        add     src1=8,src0     // 2nd src pointer
 144        cmp.le  p6,p0=8,tmp
 145        ;;
 146        cmp.le  p7,p0=16,tmp
 147        mov     ar.lc=cnt       // loop setup
 148        cmp.eq  p16,p17 = r0,r0
 149        mov     ar.ec=2
 150(p10)   br.dpnt.few .aligned_src_tail
 151        ;;
 152        TEXT_ALIGN(32)
 1531:
 154EX(.ex_handler, (p16)   ld8     r34=[src0],16)
 155EK(.ex_handler, (p16)   ld8     r38=[src1],16)
 156EX(.ex_handler, (p17)   st8     [dst0]=r33,16)
 157EK(.ex_handler, (p17)   st8     [dst1]=r37,16)
 158        ;;
 159EX(.ex_handler, (p16)   ld8     r32=[src0],16)
 160EK(.ex_handler, (p16)   ld8     r36=[src1],16)
 161EX(.ex_handler, (p16)   st8     [dst0]=r34,16)
 162EK(.ex_handler, (p16)   st8     [dst1]=r38,16)
 163        br.ctop.dptk.few 1b
 164        ;;
 165
 166.aligned_src_tail:
 167EX(.ex_handler, (p6)    ld8     t1=[src0])
 168        mov     ar.lc=saved_lc
 169        mov     ar.pfs=saved_pfs
 170EX(.ex_hndlr_s, (p7)    ld8     t2=[src1],8)
 171        cmp.le  p8,p0=24,tmp
 172        and     r21=-8,tmp
 173        ;;
 174EX(.ex_hndlr_s, (p8)    ld8     t3=[src1])
 175EX(.ex_handler, (p6)    st8     [dst0]=t1)      // store byte 1
 176        and     in2=7,tmp       // remaining length
 177EX(.ex_hndlr_d, (p7)    st8     [dst1]=t2,8)    // store byte 2
 178        add     src0=src0,r21   // setting up src pointer
 179        add     dst0=dst0,r21   // setting up dest pointer
 180        ;;
 181EX(.ex_handler, (p8)    st8     [dst1]=t3)      // store byte 3
 182        mov     pr=saved_pr,-1
 183        br.dptk.many .memcpy_short
 184        ;;
 185
 186/* code taken from copy_page_mck */
 187.long_copy:
 188        .rotr v[2*PREFETCH_DIST]
 189        .rotp p[N]
 190
 191        mov src_pre_mem = src0
 192        mov pr.rot = 0x10000
 193        mov ar.ec = 1                           // special unrolled loop
 194
 195        mov dst_pre_mem = dst0
 196
 197        add src_pre_l2 = 8*8, src0
 198        add dst_pre_l2 = 8*8, dst0
 199        ;;
 200        add src0 = 8, src_pre_mem               // first t1 src
 201        mov ar.lc = 2*PREFETCH_DIST - 1
 202        shr.u cnt=in2,7                         // number of lines
 203        add src1 = 3*8, src_pre_mem             // first t3 src
 204        add dst0 = 8, dst_pre_mem               // first t1 dst
 205        add dst1 = 3*8, dst_pre_mem             // first t3 dst
 206        ;;
 207        and tmp=127,in2                         // remaining bytes after this block
 208        add cnt = -(2*PREFETCH_DIST) - 1, cnt
 209        // same as .line_copy loop, but with all predicated-off instructions removed:
 210.prefetch_loop:
 211EX(.ex_hndlr_lcpy_1, (p[A])     ld8 v[A] = [src_pre_mem], 128)          // M0
 212EK(.ex_hndlr_lcpy_1, (p[B])     st8 [dst_pre_mem] = v[B], 128)          // M2
 213        br.ctop.sptk .prefetch_loop
 214        ;;
 215        cmp.eq p16, p0 = r0, r0                 // reset p16 to 1
 216        mov ar.lc = cnt
 217        mov ar.ec = N                           // # of stages in pipeline
 218        ;;
 219.line_copy:
 220EX(.ex_handler, (p[D])  ld8 t2 = [src0], 3*8)                   // M0
 221EK(.ex_handler, (p[D])  ld8 t4 = [src1], 3*8)                   // M1
 222EX(.ex_handler_lcpy,    (p[B])  st8 [dst_pre_mem] = v[B], 128)          // M2 prefetch dst from memory
 223EK(.ex_handler_lcpy,    (p[D])  st8 [dst_pre_l2] = n8, 128)             // M3 prefetch dst from L2
 224        ;;
 225EX(.ex_handler_lcpy,    (p[A])  ld8 v[A] = [src_pre_mem], 128)          // M0 prefetch src from memory
 226EK(.ex_handler_lcpy,    (p[C])  ld8 n8 = [src_pre_l2], 128)             // M1 prefetch src from L2
 227EX(.ex_handler, (p[D])  st8 [dst0] =  t1, 8)                    // M2
 228EK(.ex_handler, (p[D])  st8 [dst1] =  t3, 8)                    // M3
 229        ;;
 230EX(.ex_handler, (p[D])  ld8  t5 = [src0], 8)
 231EK(.ex_handler, (p[D])  ld8  t7 = [src1], 3*8)
 232EX(.ex_handler, (p[D])  st8 [dst0] =  t2, 3*8)
 233EK(.ex_handler, (p[D])  st8 [dst1] =  t4, 3*8)
 234        ;;
 235EX(.ex_handler, (p[D])  ld8  t6 = [src0], 3*8)
 236EK(.ex_handler, (p[D])  ld8 t10 = [src1], 8)
 237EX(.ex_handler, (p[D])  st8 [dst0] =  t5, 8)
 238EK(.ex_handler, (p[D])  st8 [dst1] =  t7, 3*8)
 239        ;;
 240EX(.ex_handler, (p[D])  ld8  t9 = [src0], 3*8)
 241EK(.ex_handler, (p[D])  ld8 t11 = [src1], 3*8)
 242EX(.ex_handler, (p[D])  st8 [dst0] =  t6, 3*8)
 243EK(.ex_handler, (p[D])  st8 [dst1] = t10, 8)
 244        ;;
 245EX(.ex_handler, (p[D])  ld8 t12 = [src0], 8)
 246EK(.ex_handler, (p[D])  ld8 t14 = [src1], 8)
 247EX(.ex_handler, (p[D])  st8 [dst0] =  t9, 3*8)
 248EK(.ex_handler, (p[D])  st8 [dst1] = t11, 3*8)
 249        ;;
 250EX(.ex_handler, (p[D])  ld8 t13 = [src0], 4*8)
 251EK(.ex_handler, (p[D])  ld8 t15 = [src1], 4*8)
 252EX(.ex_handler, (p[D])  st8 [dst0] = t12, 8)
 253EK(.ex_handler, (p[D])  st8 [dst1] = t14, 8)
 254        ;;
 255EX(.ex_handler, (p[C])  ld8  t1 = [src0], 8)
 256EK(.ex_handler, (p[C])  ld8  t3 = [src1], 8)
 257EX(.ex_handler, (p[D])  st8 [dst0] = t13, 4*8)
 258EK(.ex_handler, (p[D])  st8 [dst1] = t15, 4*8)
 259        br.ctop.sptk .line_copy
 260        ;;
 261
 262        add dst0=-8,dst0
 263        add src0=-8,src0
 264        mov in2=tmp
 265        .restore sp
 266        br.sptk.many .medium_copy
 267        ;;
 268
 269#define BLOCK_SIZE      128*32
 270#define blocksize       r23
 271#define curlen          r24
 272
 273// dest is on 8-byte boundary, src is not. We need to do
 274// ld8-ld8, shrp, then st8.  Max 8 byte copy per cycle.
 275.unaligned_src:
 276        .prologue
 277        .save ar.pfs, saved_pfs
 278        alloc   saved_pfs=ar.pfs,3,5,0,8
 279        .save ar.lc, saved_lc
 280        mov     saved_lc=ar.lc
 281        .save pr, saved_pr
 282        mov     saved_pr=pr
 283        .body
 284.4k_block:
 285        mov     saved_in0=dst0  // need to save all input arguments
 286        mov     saved_in2=in2
 287        mov     blocksize=BLOCK_SIZE
 288        ;;
 289        cmp.lt  p6,p7=blocksize,in2
 290        mov     saved_in1=src0
 291        ;;
 292(p6)    mov     in2=blocksize
 293        ;;
 294        shr.u   r21=in2,7       // this much cache line
 295        shr.u   r22=in2,4       // number of 16-byte iteration
 296        and     curlen=15,in2   // copy length after iteration
 297        and     r30=7,src0      // source alignment
 298        ;;
 299        cmp.lt  p7,p8=1,r21
 300        add     cnt=-1,r21
 301        ;;
 302
 303        add     src_pre_mem=0,src0      // prefetch src pointer
 304        add     dst_pre_mem=0,dst0      // prefetch dest pointer
 305        and     src0=-8,src0            // 1st src pointer
 306(p7)    mov     ar.lc = cnt
 307(p8)    mov     ar.lc = r0
 308        ;;
 309        TEXT_ALIGN(32)
 3101:      lfetch.fault      [src_pre_mem], 128
 311        lfetch.fault.excl [dst_pre_mem], 128
 312        br.cloop.dptk.few 1b
 313        ;;
 314
 315        shladd  dst1=r22,3,dst0 // 2nd dest pointer
 316        shladd  src1=r22,3,src0 // 2nd src pointer
 317        cmp.eq  p8,p9=r22,r0    // do we really need to loop?
 318        cmp.le  p6,p7=8,curlen; // have at least 8 byte remaining?
 319        add     cnt=-1,r22      // ctop iteration adjustment
 320        ;;
 321EX(.ex_handler, (p9)    ld8     r33=[src0],8)   // loop primer
 322EK(.ex_handler, (p9)    ld8     r37=[src1],8)
 323(p8)    br.dpnt.few .noloop
 324        ;;
 325
 326// The jump address is calculated based on src alignment. The COPYU
 327// macro below need to confine its size to power of two, so an entry
 328// can be caulated using shl instead of an expensive multiply. The
 329// size is then hard coded by the following #define to match the
 330// actual size.  This make it somewhat tedious when COPYU macro gets
 331// changed and this need to be adjusted to match.
 332#define LOOP_SIZE 6
 3331:
 334        mov     r29=ip          // jmp_table thread
 335        mov     ar.lc=cnt
 336        ;;
 337        add     r29=.jump_table - 1b - (.jmp1-.jump_table), r29
 338        shl     r28=r30, LOOP_SIZE      // jmp_table thread
 339        mov     ar.ec=2         // loop setup
 340        ;;
 341        add     r29=r29,r28             // jmp_table thread
 342        cmp.eq  p16,p17=r0,r0
 343        ;;
 344        mov     b6=r29                  // jmp_table thread
 345        ;;
 346        br.cond.sptk.few b6
 347
 348// for 8-15 byte case
 349// We will skip the loop, but need to replicate the side effect
 350// that the loop produces.
 351.noloop:
 352EX(.ex_handler, (p6)    ld8     r37=[src1],8)
 353        add     src0=8,src0
 354(p6)    shl     r25=r30,3
 355        ;;
 356EX(.ex_handler, (p6)    ld8     r27=[src1])
 357(p6)    shr.u   r28=r37,r25
 358(p6)    sub     r26=64,r25
 359        ;;
 360(p6)    shl     r27=r27,r26
 361        ;;
 362(p6)    or      r21=r28,r27
 363
 364.unaligned_src_tail:
 365/* check if we have more than blocksize to copy, if so go back */
 366        cmp.gt  p8,p0=saved_in2,blocksize
 367        ;;
 368(p8)    add     dst0=saved_in0,blocksize
 369(p8)    add     src0=saved_in1,blocksize
 370(p8)    sub     in2=saved_in2,blocksize
 371(p8)    br.dpnt .4k_block
 372        ;;
 373
 374/* we have up to 15 byte to copy in the tail.
 375 * part of work is already done in the jump table code
 376 * we are at the following state.
 377 * src side:
 378 * 
 379 *   xxxxxx xx                   <----- r21 has xxxxxxxx already
 380 * -------- -------- --------
 381 * 0        8        16
 382 *          ^
 383 *          |
 384 *          src1
 385 * 
 386 * dst
 387 * -------- -------- --------
 388 * ^
 389 * |
 390 * dst1
 391 */
 392EX(.ex_handler, (p6)    st8     [dst1]=r21,8)   // more than 8 byte to copy
 393(p6)    add     curlen=-8,curlen        // update length
 394        mov     ar.pfs=saved_pfs
 395        ;;
 396        mov     ar.lc=saved_lc
 397        mov     pr=saved_pr,-1
 398        mov     in2=curlen      // remaining length
 399        mov     dst0=dst1       // dest pointer
 400        add     src0=src1,r30   // forward by src alignment
 401        ;;
 402
 403// 7 byte or smaller.
 404.memcpy_short:
 405        cmp.le  p8,p9   = 1,in2
 406        cmp.le  p10,p11 = 2,in2
 407        cmp.le  p12,p13 = 3,in2
 408        cmp.le  p14,p15 = 4,in2
 409        add     src1=1,src0     // second src pointer
 410        add     dst1=1,dst0     // second dest pointer
 411        ;;
 412
 413EX(.ex_handler_short, (p8)      ld1     t1=[src0],2)
 414EK(.ex_handler_short, (p10)     ld1     t2=[src1],2)
 415(p9)    br.ret.dpnt rp          // 0 byte copy
 416        ;;
 417
 418EX(.ex_handler_short, (p8)      st1     [dst0]=t1,2)
 419EK(.ex_handler_short, (p10)     st1     [dst1]=t2,2)
 420(p11)   br.ret.dpnt rp          // 1 byte copy
 421
 422EX(.ex_handler_short, (p12)     ld1     t3=[src0],2)
 423EK(.ex_handler_short, (p14)     ld1     t4=[src1],2)
 424(p13)   br.ret.dpnt rp          // 2 byte copy
 425        ;;
 426
 427        cmp.le  p6,p7   = 5,in2
 428        cmp.le  p8,p9   = 6,in2
 429        cmp.le  p10,p11 = 7,in2
 430
 431EX(.ex_handler_short, (p12)     st1     [dst0]=t3,2)
 432EK(.ex_handler_short, (p14)     st1     [dst1]=t4,2)
 433(p15)   br.ret.dpnt rp          // 3 byte copy
 434        ;;
 435
 436EX(.ex_handler_short, (p6)      ld1     t5=[src0],2)
 437EK(.ex_handler_short, (p8)      ld1     t6=[src1],2)
 438(p7)    br.ret.dpnt rp          // 4 byte copy
 439        ;;
 440
 441EX(.ex_handler_short, (p6)      st1     [dst0]=t5,2)
 442EK(.ex_handler_short, (p8)      st1     [dst1]=t6,2)
 443(p9)    br.ret.dptk rp          // 5 byte copy
 444
 445EX(.ex_handler_short, (p10)     ld1     t7=[src0],2)
 446(p11)   br.ret.dptk rp          // 6 byte copy
 447        ;;
 448
 449EX(.ex_handler_short, (p10)     st1     [dst0]=t7,2)
 450        br.ret.dptk rp          // done all cases
 451
 452
 453/* Align dest to nearest 8-byte boundary. We know we have at
 454 * least 7 bytes to copy, enough to crawl to 8-byte boundary.
 455 * Actual number of byte to crawl depend on the dest alignment.
 456 * 7 byte or less is taken care at .memcpy_short
 457
 458 * src0 - source even index
 459 * src1 - source  odd index
 460 * dst0 - dest even index
 461 * dst1 - dest  odd index
 462 * r30  - distance to 8-byte boundary
 463 */
 464
 465.align_dest:
 466        add     src1=1,in1      // source odd index
 467        cmp.le  p7,p0 = 2,r30   // for .align_dest
 468        cmp.le  p8,p0 = 3,r30   // for .align_dest
 469EX(.ex_handler_short, (p6)      ld1     t1=[src0],2)
 470        cmp.le  p9,p0 = 4,r30   // for .align_dest
 471        cmp.le  p10,p0 = 5,r30
 472        ;;
 473EX(.ex_handler_short, (p7)      ld1     t2=[src1],2)
 474EK(.ex_handler_short, (p8)      ld1     t3=[src0],2)
 475        cmp.le  p11,p0 = 6,r30
 476EX(.ex_handler_short, (p6)      st1     [dst0] = t1,2)
 477        cmp.le  p12,p0 = 7,r30
 478        ;;
 479EX(.ex_handler_short, (p9)      ld1     t4=[src1],2)
 480EK(.ex_handler_short, (p10)     ld1     t5=[src0],2)
 481EX(.ex_handler_short, (p7)      st1     [dst1] = t2,2)
 482EK(.ex_handler_short, (p8)      st1     [dst0] = t3,2)
 483        ;;
 484EX(.ex_handler_short, (p11)     ld1     t6=[src1],2)
 485EK(.ex_handler_short, (p12)     ld1     t7=[src0],2)
 486        cmp.eq  p6,p7=r28,r29
 487EX(.ex_handler_short, (p9)      st1     [dst1] = t4,2)
 488EK(.ex_handler_short, (p10)     st1     [dst0] = t5,2)
 489        sub     in2=in2,r30
 490        ;;
 491EX(.ex_handler_short, (p11)     st1     [dst1] = t6,2)
 492EK(.ex_handler_short, (p12)     st1     [dst0] = t7)
 493        add     dst0=in0,r30    // setup arguments
 494        add     src0=in1,r30
 495(p6)    br.cond.dptk .aligned_src
 496(p7)    br.cond.dpnt .unaligned_src
 497        ;;
 498
 499/* main loop body in jump table format */
 500#define COPYU(shift)                                                                    \
 5011:                                                                                      \
 502EX(.ex_handler,  (p16)  ld8     r32=[src0],8);          /* 1 */                         \
 503EK(.ex_handler,  (p16)  ld8     r36=[src1],8);                                          \
 504                 (p17)  shrp    r35=r33,r34,shift;;     /* 1 */                         \
 505EX(.ex_handler,  (p6)   ld8     r22=[src1]);    /* common, prime for tail section */    \
 506                 nop.m  0;                                                              \
 507                 (p16)  shrp    r38=r36,r37,shift;                                      \
 508EX(.ex_handler,  (p17)  st8     [dst0]=r35,8);          /* 1 */                         \
 509EK(.ex_handler,  (p17)  st8     [dst1]=r39,8);                                          \
 510                 br.ctop.dptk.few 1b;;                                                  \
 511                 (p7)   add     src1=-8,src1;   /* back out for <8 byte case */         \
 512                 shrp   r21=r22,r38,shift;      /* speculative work */                  \
 513                 br.sptk.few .unaligned_src_tail /* branch out of jump table */         \
 514                 ;;
 515        TEXT_ALIGN(32)
 516.jump_table:
 517        COPYU(8)        // unaligned cases
 518.jmp1:
 519        COPYU(16)
 520        COPYU(24)
 521        COPYU(32)
 522        COPYU(40)
 523        COPYU(48)
 524        COPYU(56)
 525
 526#undef A
 527#undef B
 528#undef C
 529#undef D
 530
 531/*
 532 * Due to lack of local tag support in gcc 2.x assembler, it is not clear which
 533 * instruction failed in the bundle.  The exception algorithm is that we
 534 * first figure out the faulting address, then detect if there is any
 535 * progress made on the copy, if so, redo the copy from last known copied
 536 * location up to the faulting address (exclusive). In the copy_from_user
 537 * case, remaining byte in kernel buffer will be zeroed.
 538 *
 539 * Take copy_from_user as an example, in the code there are multiple loads
 540 * in a bundle and those multiple loads could span over two pages, the
 541 * faulting address is calculated as page_round_down(max(src0, src1)).
 542 * This is based on knowledge that if we can access one byte in a page, we
 543 * can access any byte in that page.
 544 *
 545 * predicate used in the exception handler:
 546 * p6-p7: direction
 547 * p10-p11: src faulting addr calculation
 548 * p12-p13: dst faulting addr calculation
 549 */
 550
 551#define A       r19
 552#define B       r20
 553#define C       r21
 554#define D       r22
 555#define F       r28
 556
 557#define memset_arg0     r32
 558#define memset_arg2     r33
 559
 560#define saved_retval    loc0
 561#define saved_rtlink    loc1
 562#define saved_pfs_stack loc2
 563
 564.ex_hndlr_s:
 565        add     src0=8,src0
 566        br.sptk .ex_handler
 567        ;;
 568.ex_hndlr_d:
 569        add     dst0=8,dst0
 570        br.sptk .ex_handler
 571        ;;
 572.ex_hndlr_lcpy_1:
 573        mov     src1=src_pre_mem
 574        mov     dst1=dst_pre_mem
 575        cmp.gtu p10,p11=src_pre_mem,saved_in1
 576        cmp.gtu p12,p13=dst_pre_mem,saved_in0
 577        ;;
 578(p10)   add     src0=8,saved_in1
 579(p11)   mov     src0=saved_in1
 580(p12)   add     dst0=8,saved_in0
 581(p13)   mov     dst0=saved_in0
 582        br.sptk .ex_handler
 583.ex_handler_lcpy:
 584        // in line_copy block, the preload addresses should always ahead
 585        // of the other two src/dst pointers.  Furthermore, src1/dst1 should
 586        // always ahead of src0/dst0.
 587        mov     src1=src_pre_mem
 588        mov     dst1=dst_pre_mem
 589.ex_handler:
 590        mov     pr=saved_pr,-1          // first restore pr, lc, and pfs
 591        mov     ar.lc=saved_lc
 592        mov     ar.pfs=saved_pfs
 593        ;;
 594.ex_handler_short: // fault occurred in these sections didn't change pr, lc, pfs
 595        cmp.ltu p6,p7=saved_in0, saved_in1      // get the copy direction
 596        cmp.ltu p10,p11=src0,src1
 597        cmp.ltu p12,p13=dst0,dst1
 598        fcmp.eq p8,p0=f6,f0             // is it memcpy?
 599        mov     tmp = dst0
 600        ;;
 601(p11)   mov     src1 = src0             // pick the larger of the two
 602(p13)   mov     dst0 = dst1             // make dst0 the smaller one
 603(p13)   mov     dst1 = tmp              // and dst1 the larger one
 604        ;;
 605(p6)    dep     F = r0,dst1,0,PAGE_SHIFT // usr dst round down to page boundary
 606(p7)    dep     F = r0,src1,0,PAGE_SHIFT // usr src round down to page boundary
 607        ;;
 608(p6)    cmp.le  p14,p0=dst0,saved_in0   // no progress has been made on store
 609(p7)    cmp.le  p14,p0=src0,saved_in1   // no progress has been made on load
 610        mov     retval=saved_in2
 611(p8)    ld1     tmp=[src1]              // force an oops for memcpy call
 612(p8)    st1     [dst1]=r0               // force an oops for memcpy call
 613(p14)   br.ret.sptk.many rp
 614
 615/*
 616 * The remaining byte to copy is calculated as:
 617 *
 618 * A =  (faulting_addr - orig_src)      -> len to faulting ld address
 619 *      or 
 620 *      (faulting_addr - orig_dst)      -> len to faulting st address
 621 * B =  (cur_dst - orig_dst)            -> len copied so far
 622 * C =  A - B                           -> len need to be copied
 623 * D =  orig_len - A                    -> len need to be zeroed
 624 */
 625(p6)    sub     A = F, saved_in0
 626(p7)    sub     A = F, saved_in1
 627        clrrrb
 628        ;;
 629        alloc   saved_pfs_stack=ar.pfs,3,3,3,0
 630        cmp.lt  p8,p0=A,r0
 631        sub     B = dst0, saved_in0     // how many byte copied so far
 632        ;;
 633(p8)    mov     A = 0;                  // A shouldn't be negative, cap it
 634        ;;
 635        sub     C = A, B
 636        sub     D = saved_in2, A
 637        ;;
 638        cmp.gt  p8,p0=C,r0              // more than 1 byte?
 639        add     memset_arg0=saved_in0, A
 640(p6)    mov     memset_arg2=0           // copy_to_user should not call memset
 641(p7)    mov     memset_arg2=D           // copy_from_user need to have kbuf zeroed
 642        mov     r8=0
 643        mov     saved_retval = D
 644        mov     saved_rtlink = b0
 645
 646        add     out0=saved_in0, B
 647        add     out1=saved_in1, B
 648        mov     out2=C
 649(p8)    br.call.sptk.few b0=__copy_user // recursive call
 650        ;;
 651
 652        add     saved_retval=saved_retval,r8    // above might return non-zero value
 653        cmp.gt  p8,p0=memset_arg2,r0    // more than 1 byte?
 654        mov     out0=memset_arg0        // *s
 655        mov     out1=r0                 // c
 656        mov     out2=memset_arg2        // n
 657(p8)    br.call.sptk.few b0=memset
 658        ;;
 659
 660        mov     retval=saved_retval
 661        mov     ar.pfs=saved_pfs_stack
 662        mov     b0=saved_rtlink
 663        br.ret.sptk.many rp
 664
 665/* end of McKinley specific optimization */
 666END(__copy_user)
 667