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Annotation of researchv10no/libc/gen/strchr.s, revision 1.1.1.1

1.1       root        1:        .file   "strchr.s"
                      2: #      @(#)strchr.s    1.5
                      3: #      3.0 SID #       1.2
                      4: # Fast assembler language version of the following C-program
                      5: #                      strchr
                      6: # which represents the `standard' for the C-library.
                      7: 
                      8: # Return the ptr in sp at which the character c appears;
                      9: #   NULL if not found
                     10: #      
                     11: #      char *
                     12: #      strchr(sp, c)
                     13: #      register char *sp, c;
                     14: #      {
                     15: #              do {
                     16: #                      if (*sp == c)
                     17: #                              return(sp);
                     18: #              } while (*sp++);
                     19: #              return(0);
                     20: #      }
                     21:        .globl  _strchr
                     22:        .text
                     23:        .align  2
                     24: _strchr:
                     25:        .word   0x0000          # pgm uses regs 0,1,2,3,4
                     26:        movq    4(ap),r2        # s1 in r2; `c' in r3
                     27: L0:
                     28:        locc    $0,$65535,(r2)  # search for a terminating null
                     29:        bneq    L1              # hop onward if we found one
                     30:        locc    r3,$65535,(r2)  # else look for `c' in this BLOCK
                     31:        bneq    L2              # hop if found (r1 points to it)
                     32:        movl    r1,r2           # no luck at all in this BLOCK
                     33:        jmp     L0              # go back to try next BLOCK
                     34: L1:
                     35:        subl3   r2,r1,r4        # length of (this segment of) s1 in r4
                     36:        incl    r4              # gotta include terminal null
                     37:        locc    r3,r4,(r2)      # scan for `c' in this (tail) segment
                     38:        beql    L3              # skip if not found! (r0 is already 0)
                     39: L2:
                     40:        movl    r1,r0           # else found one, return pointer to user
                     41: L3:
                     42:        ret

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