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      1 
      2 #include <stdio.h>
      3 #include <stdlib.h>
      4 #include <assert.h>
      5 
      6 typedef unsigned int UInt;
      7 
      8 /* Given a word, do bt/bts/btr/btc on bits 0, 1, 2 and 3 of it, and
      9    also reconstruct the original bits 0, 1, 2, 3 by looking at the
     10    carry flag.  Returned result has mashed bits 0-3 at the bottom and
     11    the reconstructed original bits 0-3 as 4-7. */
     12 UInt mash_reg_L ( UInt orig )
     13 {
     14   UInt reconstructed, mashed;
     15   __asm__ __volatile__ (
     16      "movl %2, %%edx\n\t"
     17      ""
     18      "movl $0, %%eax\n\t"
     19      "\n\t"
     20      "btl  $0, %%edx\n\t"
     21      "setb %%cl\n\t"
     22      "movzbl %%cl, %%ecx\n\t"
     23      "orl %%ecx, %%eax\n\t"
     24      "\n\t"
     25      "btsl $1, %%edx\n\t"
     26      "setb %%cl\n\t"
     27      "movzbl %%cl, %%ecx\n\t"
     28      "shll $1, %%ecx\n\t"
     29      "orl %%ecx, %%eax\n\t"
     30      "\n\t"
     31      "btrl $2, %%edx\n\t"
     32      "setb %%cl\n\t"
     33      "movzbl %%cl, %%ecx\n\t"
     34      "shll $2, %%ecx\n\t"
     35      "orl %%ecx, %%eax\n\t"
     36      "\n\t"
     37      "btcl $3, %%edx\n\t"
     38      "setb %%cl\n\t"
     39      "movzbl %%cl, %%ecx\n\t"
     40      "shll $3, %%ecx\n\t"
     41      "orl %%ecx, %%eax\n\t"
     42      "\n\t"
     43      "movl %%eax, %0\n\t"
     44      "movl %%edx, %1"
     45 
     46      : "=r" (reconstructed), "=r" (mashed)
     47      : "r" (orig)
     48      : "eax", "ecx", "edx", "cc");
     49   return (mashed & 0xF) | ((reconstructed & 0xF) << 4);
     50 }
     51 
     52 
     53 
     54 
     55 UInt mash_mem_L ( int* origp )
     56 {
     57   UInt reconstructed, mashed;
     58   __asm__ __volatile__ (
     59      "movl %2, %%edx\n\t"
     60      ""
     61      "movl $0, %%eax\n\t"
     62      "\n\t"
     63      "btl  $0, (%%edx)\n\t"
     64      "setb %%cl\n\t"
     65      "movzbl %%cl, %%ecx\n\t"
     66      "orl %%ecx, %%eax\n\t"
     67      "\n\t"
     68      "btsl $1, (%%edx)\n\t"
     69      "setb %%cl\n\t"
     70      "movzbl %%cl, %%ecx\n\t"
     71      "shll $1, %%ecx\n\t"
     72      "orl %%ecx, %%eax\n\t"
     73      "\n\t"
     74      "btrl $2, (%%edx)\n\t"
     75      "setb %%cl\n\t"
     76      "movzbl %%cl, %%ecx\n\t"
     77      "shll $2, %%ecx\n\t"
     78      "orl %%ecx, %%eax\n\t"
     79      "\n\t"
     80      "btcl $3, (%%edx)\n\t"
     81      "setb %%cl\n\t"
     82      "movzbl %%cl, %%ecx\n\t"
     83      "shll $3, %%ecx\n\t"
     84      "orl %%ecx, %%eax\n\t"
     85      "\n\t"
     86      "movl %%eax, %0\n\t"
     87      "movl (%%edx), %1"
     88 
     89      : "=r" (reconstructed), "=r" (mashed)
     90      : "r" (origp)
     91      : "eax", "ecx", "edx", "cc");
     92   return (mashed & 0xF) | ((reconstructed & 0xF) << 4);
     93 }
     94 
     95 
     96 
     97 UInt mash_reg_W ( UInt orig )
     98 {
     99   UInt reconstructed, mashed;
    100   __asm__ __volatile__ (
    101      "movl %2, %%edx\n\t"
    102      ""
    103      "movl $0, %%eax\n\t"
    104      "\n\t"
    105      "btw  $0, %%dx\n\t"
    106      "setb %%cl\n\t"
    107      "movzbl %%cl, %%ecx\n\t"
    108      "orl %%ecx, %%eax\n\t"
    109      "\n\t"
    110      "btsw $1, %%dx\n\t"
    111      "setb %%cl\n\t"
    112      "movzbl %%cl, %%ecx\n\t"
    113      "shll $1, %%ecx\n\t"
    114      "orl %%ecx, %%eax\n\t"
    115      "\n\t"
    116      "btrw $2, %%dx\n\t"
    117      "setb %%cl\n\t"
    118      "movzbl %%cl, %%ecx\n\t"
    119      "shll $2, %%ecx\n\t"
    120      "orl %%ecx, %%eax\n\t"
    121      "\n\t"
    122      "btcw $3, %%dx\n\t"
    123      "setb %%cl\n\t"
    124      "movzbl %%cl, %%ecx\n\t"
    125      "shll $3, %%ecx\n\t"
    126      "orl %%ecx, %%eax\n\t"
    127      "\n\t"
    128      "movl %%eax, %0\n\t"
    129      "movl %%edx, %1"
    130 
    131      : "=r" (reconstructed), "=r" (mashed)
    132      : "r" (orig)
    133      : "eax", "ecx", "edx", "cc");
    134   return (mashed & 0xF) | ((reconstructed & 0xF) << 4);
    135 }
    136 
    137 
    138 
    139 
    140 int main ( void )
    141 {
    142   int i, ii;
    143   for (i = 0; i < 0x10; i++) {
    144     ii = i;
    145     printf("0x%x -> 0x%2x 0x%2x 0x%2x\n", i,
    146            mash_reg_L(i), mash_mem_L(&ii), mash_reg_W(i));
    147   }
    148   return 1;
    149 }
    150 
    151