FFmpeg
vorbisdsp_altivec.c
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1 /*
2  * Copyright (c) 2006 Luca Barbato <lu_zero@gentoo.org>
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include "config.h"
22 
23 #include "libavutil/attributes.h"
24 #include "libavutil/cpu.h"
25 #include "libavutil/ppc/cpu.h"
27 
28 #include "libavcodec/vorbisdsp.h"
29 
30 #if HAVE_ALTIVEC
31 static void vorbis_inverse_coupling_altivec(float *mag, float *ang,
32  intptr_t blocksize)
33 {
34  int i;
35  vector float m, a;
36  vector bool int t0, t1;
37  const vector unsigned int v_31 = //XXX
38  vec_add(vec_add(vec_splat_u32(15),vec_splat_u32(15)),vec_splat_u32(1));
39  for (i = 0; i < blocksize; i += 4) {
40  m = vec_ld(0, mag+i);
41  a = vec_ld(0, ang+i);
42  t0 = vec_cmple(m, (vector float)vec_splat_u32(0));
43  t1 = vec_cmple(a, (vector float)vec_splat_u32(0));
44  a = vec_xor(a, (vector float) vec_sl((vector unsigned int)t0, v_31));
45  t0 = (vector bool int)vec_and(a, t1);
46  t1 = (vector bool int)vec_andc(a, t1);
47  a = vec_sub(m, (vector float)t1);
48  m = vec_add(m, (vector float)t0);
49  vec_stl(a, 0, ang+i);
50  vec_stl(m, 0, mag+i);
51  }
52 }
53 #endif /* HAVE_ALTIVEC */
54 
56 {
57 #if HAVE_ALTIVEC
59  return;
60 
61  c->vorbis_inverse_coupling = vorbis_inverse_coupling_altivec;
62 #endif /* HAVE_ALTIVEC */
63 }
The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a
Definition: undefined.txt:36
Macro definitions for various function/variable attributes.
#define av_cold
Definition: attributes.h:82
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
#define t0
Definition: regdef.h:28
void(* vorbis_inverse_coupling)(float *mag, float *ang, intptr_t blocksize)
Definition: vorbisdsp.h:26
av_cold void ff_vorbisdsp_init_ppc(VorbisDSPContext *c)
#define PPC_ALTIVEC(flags)
Definition: cpu.h:25
#define t1
Definition: regdef.h:29
int av_get_cpu_flags(void)
Return the flags which specify extensions supported by the CPU.
Definition: cpu.c:93
Contains misc utility macros and inline functions.
int