root/arch/alpha/lib/strchr.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * arch/alpha/lib/strchr.S
   4  * Contributed by Richard Henderson (rth@tamu.edu)
   5  *
   6  * Return the address of a given character within a null-terminated
   7  * string, or null if it is not found.
   8  */
   9 #include <asm/export.h>
  10 #include <asm/regdef.h>
  11 
  12         .set noreorder
  13         .set noat
  14 
  15         .align 3
  16         .globl strchr
  17         .ent strchr
  18 strchr:
  19         .frame sp, 0, ra
  20         .prologue 0
  21 
  22         zapnot  a1, 1, a1       # e0    : zero extend the search character
  23         ldq_u   t0, 0(a0)       # .. e1 : load first quadword
  24         sll     a1, 8, t5       # e0    : replicate the search character
  25         andnot  a0, 7, v0       # .. e1 : align our loop pointer
  26         or      t5, a1, a1      # e0    :
  27         lda     t4, -1          # .. e1 : build garbage mask
  28         sll     a1, 16, t5      # e0    :
  29         cmpbge  zero, t0, t2    # .. e1 : bits set iff byte == zero
  30         mskqh   t4, a0, t4      # e0    :
  31         or      t5, a1, a1      # .. e1 :
  32         sll     a1, 32, t5      # e0    :
  33         cmpbge  zero, t4, t4    # .. e1 : bits set iff byte is garbage
  34         or      t5, a1, a1      # e0    :
  35         xor     t0, a1, t1      # .. e1 : make bytes == c zero
  36         cmpbge  zero, t1, t3    # e0    : bits set iff byte == c
  37         or      t2, t3, t0      # e1    : bits set iff char match or zero match
  38         andnot  t0, t4, t0      # e0    : clear garbage bits
  39         bne     t0, $found      # .. e1 (zdb)
  40 
  41 $loop:  ldq     t0, 8(v0)       # e0    :
  42         addq    v0, 8, v0       # .. e1 :
  43         nop                     # e0    :
  44         xor     t0, a1, t1      # .. e1 (ev5 data stall)
  45         cmpbge  zero, t0, t2    # e0    : bits set iff byte == 0
  46         cmpbge  zero, t1, t3    # .. e1 : bits set iff byte == c
  47         or      t2, t3, t0      # e0    :
  48         beq     t0, $loop       # .. e1 (zdb)
  49 
  50 $found: negq    t0, t1          # e0    : clear all but least set bit
  51         and     t0, t1, t0      # e1 (stall)
  52 
  53         and     t0, t3, t1      # e0    : bit set iff byte was the char
  54         beq     t1, $retnull    # .. e1 (zdb)
  55 
  56         and     t0, 0xf0, t2    # e0    : binary search for that set bit
  57         and     t0, 0xcc, t3    # .. e1 :
  58         and     t0, 0xaa, t4    # e0    :
  59         cmovne  t2, 4, t2       # .. e1 :
  60         cmovne  t3, 2, t3       # e0    :
  61         cmovne  t4, 1, t4       # .. e1 :
  62         addq    t2, t3, t2      # e0    :
  63         addq    v0, t4, v0      # .. e1 :
  64         addq    v0, t2, v0      # e0    :
  65         ret                     # .. e1 :
  66 
  67 $retnull:
  68         mov     zero, v0        # e0    :
  69         ret                     # .. e1 :
  70 
  71         .end strchr
  72         EXPORT_SYMBOL(strchr)