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5ce98c3f | 1 | /* llround function. PowerPC64 version. |
688903eb | 2 | Copyright (C) 2004-2018 Free Software Foundation, Inc. |
5ce98c3f UD |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 PE |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
5ce98c3f UD |
18 | |
19 | #include <sysdep.h> | |
f964490f | 20 | #include <math_ldbl_opt.h> |
d17542d2 | 21 | #include <libm-alias-double.h> |
5ce98c3f UD |
22 | |
23 | .section ".toc","aw" | |
c1e6b459 UD |
24 | .LC0: /* 2^52 */ |
25 | .tc FD_43300000_0[TC],0x4330000000000000 | |
5ce98c3f UD |
26 | .LC1: /* 0.5 */ |
27 | .tc FD_3fe00000_0[TC],0x3fe0000000000000 | |
28 | .section ".text" | |
9c84384c | 29 | |
c1e6b459 | 30 | /* long long [r3] llround (double x [fp1]) |
9c84384c | 31 | IEEE 1003.1 llround function. IEEE specifies "round to the nearest |
5ce98c3f UD |
32 | integer value, rounding halfway cases away from zero, regardless of |
33 | the current rounding mode." However PowerPC Architecture defines | |
9c84384c JM |
34 | "round to Nearest" as "Choose the best approximation. In case of a |
35 | tie, choose the one that is even (least significant bit o).". | |
5ce98c3f UD |
36 | So we can't use the PowerPC "round to Nearest" mode. Instead we set |
37 | "round toward Zero" mode and round by adding +-0.5 before rounding | |
c1e6b459 UD |
38 | to the integer value. |
39 | ||
40 | It is necessary to detect when x is (+-)0x1.fffffffffffffp-2 | |
41 | because adding +-0.5 in this case will cause an erroneous shift, | |
42 | carry and round. We simply return 0 if 0.5 > x > -0.5. Likewise | |
43 | if x is and odd number between +-(2^52 and 2^53-1) a shift and | |
44 | carry will erroneously round if biased with +-0.5. Therefore if x | |
45 | is greater/less than +-2^52 we don't need to bias the number with | |
46 | +-0.5. */ | |
5ce98c3f UD |
47 | |
48 | ENTRY (__llround) | |
d7d06f79 | 49 | CALL_MCOUNT 0 |
c1e6b459 UD |
50 | lfd fp9,.LC0@toc(2) /* Load 2^52 into fpr9. */ |
51 | lfd fp10,.LC1@toc(2)/* Load 0.5 into fpr10. */ | |
52 | fabs fp2,fp1 /* Get the absolute value of x. */ | |
53 | fsub fp12,fp10,fp10 /* Compute 0.0 into fp12. */ | |
54 | fcmpu cr6,fp2,fp10 /* if |x| < 0.5 */ | |
9ea8bfec UD |
55 | fcmpu cr7,fp2,fp9 /* if |x| >= 2^52 */ |
56 | fcmpu cr1,fp1,fp12 /* x is negative? x < 0.0 */ | |
c1e6b459 | 57 | blt- cr6,.Lretzero /* 0.5 > x < -0.5 so just return 0. */ |
9ea8bfec | 58 | bge- cr7,.Lnobias /* 2^52 > x < -2^52 just convert with no bias. */ |
32b71ad3 JM |
59 | /* Test whether an integer to avoid spurious "inexact". */ |
60 | fadd fp3,fp2,fp9 | |
61 | fsub fp3,fp3,fp9 | |
62 | fcmpu cr5,fp2,fp3 | |
63 | beq cr5,.Lnobias | |
c1e6b459 | 64 | fadd fp3,fp2,fp10 /* |x|+=0.5 bias to prepare to round. */ |
9ea8bfec | 65 | bge cr1,.Lconvert /* x is positive so don't negate x. */ |
c1e6b459 UD |
66 | fnabs fp3,fp3 /* -(|x|+=0.5) */ |
67 | .Lconvert: | |
68 | fctidz fp4,fp3 /* Convert to Integer double word round toward 0. */ | |
69 | stfd fp4,-16(r1) | |
70 | nop | |
71 | nop | |
5ce98c3f | 72 | nop |
c1e6b459 UD |
73 | ld r3,-16(r1) /* Load return as integer. */ |
74 | .Lout: | |
5ce98c3f | 75 | blr |
c1e6b459 UD |
76 | .Lretzero: /* 0.5 > x > -0.5 */ |
77 | li r3,0 /* return 0. */ | |
78 | b .Lout | |
79 | .Lnobias: | |
80 | fmr fp3,fp1 | |
81 | b .Lconvert | |
5ce98c3f UD |
82 | END (__llround) |
83 | ||
84 | strong_alias (__llround, __lround) | |
d17542d2 JM |
85 | libm_alias_double (__llround, llround) |
86 | libm_alias_double (__lround, lround) |