LXR linux/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
  18strchr:
  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)
  73