xref: /reactos/sdk/lib/crt/math/amd64/sqrt.S (revision d8c6ef5e) 
1/*
2 * COPYRIGHT:         See COPYING in the top level directory
3 * PROJECT:           ReactOS system libraries
4 * PURPOSE:           Implementation of sqrt
5 * FILE:              lib/sdk/crt/math/amd64/sqrt.S
6 * PROGRAMMER:        Timo Kreuzer (timo.kreuzer@reactos.org)
7 */
8
9/* INCLUDES ******************************************************************/
10
11#include <asm.inc>
12
13/* CODE **********************************************************************/
14.code64
15
16PUBLIC sqrt
17sqrt:
18
19    /* Load the sign bit into rdx */
20    mov rdx, HEX(8000000000000000)
21
22    /* Move the lower 64 bits of xmm0 into rax */
23    movd rax, xmm0
24
25    /* Test the sign bit */
26    test rax, rdx
27
28    /* If it is set, go to the failure path */
29    jnz x_is_negative
30
31    /* x is positive, now check if it is NaN by checking if the unsigned
32       integer value is larger than the highest valid positive value. */
33    mov rcx, HEX(7FF0000000000000)
34    cmp rax, rcx
35    ja short x_is_nan
36
37    /* All is well, calculate the sqrt */
38    sqrtpd xmm0, xmm0
39    ret
40
41x_is_negative:
42    /* Load failure return value (-1.#IND00) into rcx */
43    mov rcx, HEX(0FFF8000000000000)
44
45    /* Check if the parameter was -0.0 */
46    cmp rax, rdx
47
48    /* If it was not, load the failure value, otherwise keep -0.0  */
49    cmovne  rax, rcx
50
51    /* Move the value back into the return register */
52    movd xmm0, rax
53    ret
54
55x_is_nan:
56    /* Create a 1.#QNAN0 by setting this bit */
57    mov rcx, HEX(8000000000000)
58    or rax, rcx
59
60    /* Move the value back into the return register */
61    movd xmm0, rax
62    ret
63
64
65END
66