| /* |
| * 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 "wtf/CPU.h" |
| #include "wtf/MathExtras.h" |
| #include <float.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(WIN) && COMPILER(MSVC) |
| #define HAVE_DENORMAL 1 |
| #endif |
| |
| #if COMPILER(GCC) && (CPU(X86) || CPU(X86_64)) |
| #define HAVE_DENORMAL 1 |
| #endif |
| |
| #if HAVE(DENORMAL) |
| class DenormalDisabler { |
| public: |
| DenormalDisabler() |
| : m_savedCSR(0) |
| { |
| #if OS(WIN) && 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 | 0x8040); |
| #endif |
| } |
| |
| ~DenormalDisabler() |
| { |
| #if OS(WIN) && 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(WIN) && 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 (fabs(f) < FLT_MIN) ? 0.0f : f; |
| #else |
| return f; |
| #endif |
| } |
| private: |
| #if COMPILER(GCC) && (CPU(X86) || CPU(X86_64)) |
| 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 { |
| 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 (fabs(f) < FLT_MIN) ? 0.0f : f; |
| } |
| }; |
| |
| #endif |
| |
| } // WebCore |
| |
| #undef HAVE_DENORMAL |
| #endif // DenormalDisabler_h |