| /* |
| * 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/Allocator.h" |
| #include "wtf/CPU.h" |
| #include "wtf/MathExtras.h" |
| #include <float.h> |
| |
| namespace blink { |
| |
| // 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) |
| // Windows compiled using MSVC with SSE2 |
| #define HAVE_DENORMAL 1 |
| #endif |
| |
| #if COMPILER(GCC) && (CPU(X86) || CPU(X86_64)) |
| // X86 chips can flush denormals |
| #define HAVE_DENORMAL 1 |
| #endif |
| |
| #if CPU(ARM) || CPU(ARM64) |
| #define HAVE_DENORMAL 1 |
| #endif |
| |
| #if HAVE(DENORMAL) |
| class DenormalDisabler { |
| DISALLOW_NEW(); |
| |
| public: |
| DenormalDisabler() : m_savedCSR(0) { disableDenormals(); } |
| |
| ~DenormalDisabler() { restoreState(); } |
| |
| // This is a nop if we can flush denormals to zero in hardware. |
| static inline float flushDenormalFloatToZero(float f) { return f; } |
| |
| private: |
| unsigned m_savedCSR; |
| |
| #if COMPILER(GCC) && (CPU(X86) || CPU(X86_64)) |
| inline void disableDenormals() { |
| m_savedCSR = getCSR(); |
| setCSR(m_savedCSR | 0x8040); |
| } |
| |
| inline void restoreState() { setCSR(m_savedCSR); } |
| |
| 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)); |
| } |
| |
| #elif OS(WIN) && COMPILER(MSVC) |
| inline void disableDenormals() { |
| // 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 unused; |
| _controlfp_s(&unused, _DN_FLUSH, _MCW_DN); |
| } |
| |
| inline void restoreState() { |
| unsigned unused; |
| _controlfp_s(&unused, m_savedCSR, _MCW_DN); |
| } |
| #elif CPU(ARM) || CPU(ARM64) |
| inline void disableDenormals() { |
| m_savedCSR = getStatusWord(); |
| // Bit 24 is the flush-to-zero mode control bit. Setting it to 1 flushes |
| // denormals to 0. |
| setStatusWord(m_savedCSR | (1 << 24)); |
| } |
| |
| inline void restoreState() { setStatusWord(m_savedCSR); } |
| |
| inline int getStatusWord() { |
| int result; |
| #if CPU(ARM64) |
| asm volatile("mrs %x[result], FPCR" : [result] "=r"(result)); |
| #else |
| asm volatile("vmrs %[result], FPSCR" : [result] "=r"(result)); |
| #endif |
| return result; |
| } |
| |
| inline void setStatusWord(int a) { |
| #if CPU(ARM64) |
| asm volatile("msr FPCR, %x[src]" : : [src] "r"(a)); |
| #else |
| asm volatile("vmsr FPSCR, %[src]" : : [src] "r"(a)); |
| #endif |
| } |
| |
| #endif |
| }; |
| |
| #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 |
| |
| } // namespace blink |
| |
| #undef HAVE_DENORMAL |
| #endif // DenormalDisabler_h |