1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/*
* Copyright (C) 2011, Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef DenormalDisabler_h
#define DenormalDisabler_h
#include <cinttypes>
#include <wtf/MathExtras.h>
#include <wtf/StdLibExtras.h>
#include <wtf/TZoneMallocInlines.h>
namespace WebCore {
// Deal with denormals. They can very seriously impact performance on x86.
// Define HAVE_DENORMAL if we support flushing denormals to zero.
#if OS(WINDOWS) && COMPILER(MSVC)
#define HAVE_DENORMAL
#endif
#if COMPILER(GCC_COMPATIBLE) && defined(__SSE__)
#define HAVE_DENORMAL
#endif
#ifdef HAVE_DENORMAL
class DenormalDisabler final {
WTF_MAKE_TZONE_ALLOCATED_INLINE(DenormalDisabler);
public:
DenormalDisabler()
: m_savedCSR(0)
{
#if OS(WINDOWS) && COMPILER(MSVC)
// Save the current state, and set mode to flush denormals.
//
// http://stackoverflow.com/questions/637175/possible-bug-in-controlfp-s-may-not-restore-control-word-correctly
_controlfp_s(&m_savedCSR, 0, 0);
unsigned int unused;
_controlfp_s(&unused, _DN_FLUSH, _MCW_DN);
#else
m_savedCSR = getCSR();
setCSR(m_savedCSR | (isDAZSupported() ? 0x8040 : 0x8000));
#endif
}
~DenormalDisabler()
{
#if OS(WINDOWS) && COMPILER(MSVC)
unsigned int unused;
_controlfp_s(&unused, m_savedCSR, _MCW_DN);
#else
setCSR(m_savedCSR);
#endif
}
// This is a nop if we can flush denormals to zero in hardware.
static inline float flushDenormalFloatToZero(float f)
{
#if OS(WINDOWS) && COMPILER(MSVC) && (!_M_IX86_FP)
// For systems using x87 instead of sse, there's no hardware support
// to flush denormals automatically. Hence, we need to flush
// denormals to zero manually.
return (std::abs(f) < FLT_MIN) ? 0.0f : f;
#else
return f;
#endif
}
private:
#if COMPILER(GCC_COMPATIBLE) && defined(__SSE__)
static inline bool isDAZSupported()
{
#if CPU(X86_64)
return true;
#else
static bool s_isInited = false;
static bool s_isSupported = false;
if (s_isInited)
return s_isSupported;
struct fxsaveResult {
uint8_t before[28];
uint32_t CSRMask;
uint8_t after[480];
} __attribute__ ((aligned (16)));
fxsaveResult registerData;
zeroBytes(registerData);
asm volatile("fxsave %0" : "=m" (registerData));
s_isSupported = registerData.CSRMask & 0x0040;
s_isInited = true;
return s_isSupported;
#endif
}
inline int getCSR()
{
int result;
asm volatile("stmxcsr %0" : "=m" (result));
return result;
}
inline void setCSR(int a)
{
int temp = a;
asm volatile("ldmxcsr %0" : : "m" (temp));
}
#endif
unsigned int m_savedCSR;
};
#else
// FIXME: add implementations for other architectures and compilers
class DenormalDisabler final {
WTF_MAKE_TZONE_ALLOCATED_INLINE(DenormalDisabler);
public:
DenormalDisabler() { }
// Assume the worst case that other architectures and compilers
// need to flush denormals to zero manually.
static inline float flushDenormalFloatToZero(float f)
{
return (std::abs(f) < FLT_MIN) ? 0.0f : f;
}
};
#endif
} // WebCore
#undef HAVE_DENORMAL
#endif // DenormalDisabler_h
|
