CL for perf tryjob

Source/wtf/MathExtras.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple 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 COMPUTER, INC. ``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 COMPUTER, INC. OR
  * 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 WTF_MathExtras_h
 #define WTF_MathExtras_h
 
+#include "wtf/Assertions.h"
 #include "wtf/CPU.h"
+#include <algorithm>
 #include <cmath>
 #include <limits>
 
 #if COMPILER(MSVC)
-#include "wtf/Assertions.h"
 #include <stdint.h>
 #endif
 
 #if OS(OPENBSD)
 #include <sys/types.h>
 #include <machine/ieee.h>
 #endif
 
 const double piDouble = M_PI;
 const float piFloat = static_cast<float>(M_PI);
@@ skipping 170 matching lines @@
 inline float rad2deg(float r)  { return r * 180.0f / piFloat; }
 inline float deg2grad(float d) { return d * 400.0f / 360.0f; }
 inline float grad2deg(float g) { return g * 360.0f / 400.0f; }
 inline float turn2deg(float t) { return t * 360.0f; }
 inline float deg2turn(float d) { return d / 360.0f; }
 inline float rad2grad(float r) { return r * 200.0f / piFloat; }
 inline float grad2rad(float g) { return g * piFloat / 200.0f; }
 inline float turn2grad(float t) { return t * 400; }
 inline float grad2turn(float g) { return g / 400; }
 
-// std::numeric_limits<T>::min() returns the smallest positive value for floating point types
-template<typename T> inline T defaultMinimumForClamp() { return std::numeric_limits<T>::min(); }
-template<> inline float defaultMinimumForClamp() { return -std::numeric_limits<float>::max(); }
-template<> inline double defaultMinimumForClamp() { return -std::numeric_limits<double>::max(); }
-template<typename T> inline T defaultMaximumForClamp() { return std::numeric_limits<T>::max(); }
+// clampTo() is implemented by templated helper classes (to allow for partial
+// template specialization) as well as several helper functions.
 
-template<typename T> inline T clampTo(double value, T min = defaultMinimumForClamp<T>(), T max = defaultMaximumForClamp<T>())
+// This helper function can be called when we know that:
+// (1) The type signednesses match so the compiler will not produce signed vs.
+//     unsigned warnings
+// (2) The default type promotions/conversions are sufficient to handle things
+//     correctly
+template<typename LimitType, typename ValueType> inline LimitType clampToDirectComparison(ValueType value, LimitType min, LimitType max)
 {
-    if (value >= static_cast<double>(max))
+    if (value >= max)
         return max;
-    if (value <= static_cast<double>(min))
-        return min;
-    return static_cast<T>(value);
-}
-template<> inline long long int clampTo(double, long long int, long long int); // clampTo does not support long long ints.
-
-inline int clampToInteger(double value)
-{
-    return clampTo<int>(value);
+    return (value <= min) ? min : static_cast<LimitType>(value);
 }
 
-inline unsigned clampToUnsigned(double value)
+// For any floating-point limits, or integral limits smaller than long long, we
+// can cast the limits to double without losing precision; then the only cases
+// where |value| can't be represented accurately as a double are the ones where
+// it's outside the limit range anyway.  So doing all comparisons as doubles
+// will give correct results.
+//
+// In some cases, we can get better performance by using
+// clampToDirectComparison().  We use a templated class to switch between these
+// two cases (instead of simply using a conditional within one function) in
+// order to only compile the clampToDirectComparison() code for cases where it
+// will actually be used; this prevents the compiler from emitting warnings
+// about unsafe code (even though we wouldn't actually be executing that code).
+template<bool canUseDirectComparison, typename LimitType, typename ValueType> class ClampToNonLongLongHelper;
+template<typename LimitType, typename ValueType> class ClampToNonLongLongHelper<true, LimitType, ValueType> {
+public:
+    static inline LimitType clampTo(ValueType value, LimitType min, LimitType max)
+    {
+        return clampToDirectComparison(value, min, max);
+    }
+};
+
+template<typename LimitType, typename ValueType> class ClampToNonLongLongHelper<false, LimitType, ValueType> {
+public:
+    static inline LimitType clampTo(ValueType value, LimitType min, LimitType max)
+    {
+        const double doubleValue = static_cast<double>(value);
+        if (doubleValue >= static_cast<double>(max))
+            return max;
+        if (doubleValue <= static_cast<double>(min))
+            return min;
+        // If the limit type is integer, we might get better performance by
+        // casting |value| (as opposed to |doubleValue|) to the limit type.
+        return std::numeric_limits<LimitType>::is_integer ? static_cast<LimitType>(value) : static_cast<LimitType>(doubleValue);
+    }
+};
+
+// The unspecialized version of this templated class handles clamping to
+// anything other than [unsigned] long long int limits.  It simply uses the
+// class above to toggle between the "fast" and "safe" clamp implementations.
+template<typename LimitType, typename ValueType> class ClampToHelper {
+public:
+    static inline LimitType clampTo(ValueType value, LimitType min, LimitType max)
+    {
+        // We only use clampToDirectComparison() when the integerness and
+        // signedness of the two types matches.
+        //
+        // If the integerness of the types doesn't match, then at best
+        // clampToDirectComparison() won't be much more efficient than the
+        // cast-everything-to-double method, since we'll need to convert to
+        // floating point anyway; at worst, we risk incorrect results when
+        // clamping a float to a 32-bit integral type due to potential precision
+        // loss.
+        //
+        // If the signedness doesn't match, clampToDirectComparison() will
+        // produce warnings about comparing signed vs. unsigned, which are apt
+        // since negative signed values will be converted to large unsigned ones
+        // and we'll get incorrect results.
+        return ClampToNonLongLongHelper<std::numeric_limits<LimitType>::is_integer == std::numeric_limits<ValueType>::is_integer && std::numeric_limits<LimitType>::is_signed == std::numeric_limits<ValueType>::is_signed, LimitType, ValueType>::clampTo(value, min, max);
+    }
+};
+
+// Clamping to [unsigned] long long int limits requires more care.  These may
+// not be accurately representable as doubles, so instead we cast |value| to the
+// limit type.  But that cast is undefined if |value| is floating point and
+// outside the representable range of the limit type, so we also have to check
+// for that case explicitly.
+template<typename ValueType> class ClampToHelper<long long int, ValueType> {
+public:
+    static inline long long int clampTo(ValueType value, long long int min, long long int max)
+    {
+        if (!std::numeric_limits<ValueType>::is_integer) {
+            if (value > 0) {
+                if (static_cast<double>(value) >= static_cast<double>(std::numeric_limits<long long int>::max()))
+                    return max;
+            } else if (static_cast<double>(value) <= static_cast<double>(std::numeric_limits<long long int>::min())) {
+                return min;
+            }
+        }
+        // Note: If |value| were unsigned long long int, it could be larger than
+        // the largest long long int, and this code would be wrong; we handle
+        // this case with a separate full specialization below.
+        return clampToDirectComparison(static_cast<long long int>(value), min, max);
+    }
+};
+
+// This specialization handles the case where the above partial specialization
+// would be potentially incorrect.
+template<> class ClampToHelper<long long int, unsigned long long int> {
+public:
+    static inline long long int clampTo(unsigned long long int value, long long int min, long long int max)
+    {
+        if (max <= 0 || value >= static_cast<unsigned long long int>(max))
+            return max;
+        const long long int longLongValue = static_cast<long long int>(value);
+        return (longLongValue <= min) ? min : longLongValue;
+    }
+};
+
+// This is similar to the partial specialization that clamps to long long int,
+// but because the lower-bound check is done for integer value types as well, we
+// don't need a <unsigned long long int, long long int> full specialization.
+template<typename ValueType> class ClampToHelper<unsigned long long int, ValueType> {
+public:
+    static inline unsigned long long int clampTo(ValueType value, unsigned long long int min, unsigned long long int max)
+    {
+        if (value <= 0)
+            return min;
+        if (!std::numeric_limits<ValueType>::is_integer) {
+            if (static_cast<double>(value) >= static_cast<double>(std::numeric_limits<unsigned long long int>::max()))
+                return max;
+        }
+        return clampToDirectComparison(static_cast<unsigned long long int>(value), min, max);
+    }
+};
+
+// This basically reimplements C++11's std::numeric_limits<T>::lowest().
+template<typename T> inline T defaultMinimumForClamp() { return std::numeric_limits<T>::min(); }
+template<> inline float defaultMinimumForClamp<float>() { return -std::numeric_limits<float>::max(); }
+template<> inline double defaultMinimumForClamp<double>() { return -std::numeric_limits<double>::max(); }
+
+// And, finally, the actual function for people to call.
+template<typename LimitType, typename ValueType> inline LimitType clampTo(ValueType value, LimitType min = defaultMinimumForClamp<LimitType>(), LimitType max = std::numeric_limits<LimitType>::max())
 {
-    return clampTo<unsigned>(value);
-}
-
-inline float clampToFloat(double value)
-{
-    return clampTo<float>(value);
-}
-
-inline int clampToPositiveInteger(double value)
-{
-    return clampTo<int>(value, 0);
-}
-
-inline int clampToInteger(float value)
-{
-    return clampTo<int>(value);
-}
-
-inline int clampToInteger(unsigned x)
-{
-    const unsigned intMax = static_cast<unsigned>(std::numeric_limits<int>::max());
-
-    if (x >= intMax)
-        return std::numeric_limits<int>::max();
-    return static_cast<int>(x);
+    ASSERT(!std::isnan(static_cast<double>(value)));
+    ASSERT(min <= max); // This also ensures |min| and |max| aren't NaN.
+    return ClampToHelper<LimitType, ValueType>::clampTo(value, min, max);
 }
 
 inline bool isWithinIntRange(float x)
 {
     return x > static_cast<float>(std::numeric_limits<int>::min()) && x < static_cast<float>(std::numeric_limits<int>::max());
 }
 
 static size_t greatestCommonDivisor(size_t a, size_t b)
 {
     return b ? greatestCommonDivisor(b, a % b) : a;
@@ skipping 51 matching lines @@
     if (i >> 2)
         log2 += 2, i >>= 2;
     if (i >> 1)
         log2 += 1;
     return log2;
 }
 
 } // namespace WTF
 
 #endif // #ifndef WTF_MathExtras_h