Fast double-to-ascii conversion.

Review URL: http://codereview.chromium.org/866002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4106 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/SConscript

@@ -63,6 +63,7 @@ SOURCES = {
     full-codegen.cc
     func-name-inferrer.cc
     global-handles.cc
+    grisu3.cc
     handles.cc
     hashmap.cc
     heap-profiler.cc

src/cached_powers.h

+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
+// OWNER 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 V8_CACHED_POWERS_H_
+#define V8_CACHED_POWERS_H_
+
+#include "diy_fp.h"
+
+namespace v8 {
+namespace internal {
+
+struct CachedPower {
+  uint64_t significand;
+  int16_t binary_exponent;
+  int16_t decimal_exponent;
+};
+
+// The following defines implement the interface between this file and the
+// generated 'powers_ten.h'.
+// GRISU_CACHE_NAME(1) contains all possible cached powers.
+// GRISU_CACHE_NAME(i) contains GRISU_CACHE_NAME(1) where only every 'i'th
+// element is kept. More formally GRISU_CACHE_NAME(i) contains the elements j*i
+// with 0 <= j < k with k such that j*k < the size of GRISU_CACHE_NAME(1).
+// The higher 'i' is the fewer elements we use.
+// Given that there are less elements, the exponent-distance between two
+// elements in the cache grows. The variable GRISU_CACHE_MAX_DISTANCE(i) stores
+// the maximum distance between two elements.
+#define GRISU_CACHE_STRUCT CachedPower
+#define GRISU_CACHE_NAME(i) kCachedPowers##i
+#define GRISU_CACHE_MAX_DISTANCE(i) kCachedPowersMaxDistance##i
+#define GRISU_CACHE_OFFSET kCachedPowerOffset
+#define GRISU_UINT64_C V8_2PART_UINT64_C
+// The following include imports the precompiled cached powers.
+#include "powers_ten.h"  // NOLINT
+
+static const double kD_1_LOG2_10 = 0.30102999566398114;  //  1 / lg(10)
+
+// We can't use a function since we reference variables depending on the 'i'.
+// This way the compiler is able to see at compile time that only one
+// cache-array variable is used and thus can remove all the others.
+#define COMPUTE_FOR_CACHE(i) \
+  if (!found && (gamma - alpha + 1 >= GRISU_CACHE_MAX_DISTANCE(i))) {   \
+    int kQ = DiyFp::kSignificandSize;                                   \
+    double k = ceiling((alpha - e + kQ - 1) * kD_1_LOG2_10);            \
+    int index = (GRISU_CACHE_OFFSET + static_cast<int>(k) - 1) / i + 1; \
+    cached_power = GRISU_CACHE_NAME(i)[index];                          \
+    found = true;                                                       \
+  }                                                                     \
+
+static void GetCachedPower(int e, int alpha, int gamma, int* mk, DiyFp* c_mk) {
+  // The following if statement should be optimized by the compiler so that only
+  // one array is referenced and the others are not included in the object file.
+  bool found = false;
+  CachedPower cached_power;
+  COMPUTE_FOR_CACHE(20);
+  COMPUTE_FOR_CACHE(19);
+  COMPUTE_FOR_CACHE(18);
+  COMPUTE_FOR_CACHE(17);
+  COMPUTE_FOR_CACHE(16);
+  COMPUTE_FOR_CACHE(15);
+  COMPUTE_FOR_CACHE(14);
+  COMPUTE_FOR_CACHE(13);
+  COMPUTE_FOR_CACHE(12);
+  COMPUTE_FOR_CACHE(11);
+  COMPUTE_FOR_CACHE(10);
+  COMPUTE_FOR_CACHE(9);
+  COMPUTE_FOR_CACHE(8);
+  COMPUTE_FOR_CACHE(7);
+  COMPUTE_FOR_CACHE(6);
+  COMPUTE_FOR_CACHE(5);
+  COMPUTE_FOR_CACHE(4);
+  COMPUTE_FOR_CACHE(3);
+  COMPUTE_FOR_CACHE(2);
+  COMPUTE_FOR_CACHE(1);
+  if (!found) {
+    UNIMPLEMENTED();
+    // Silence compiler warnings.
+    cached_power.significand = 0;
+    cached_power.binary_exponent = 0;
+    cached_power.decimal_exponent = 0;
+  }
+  *c_mk = DiyFp(cached_power.significand, cached_power.binary_exponent);
+  *mk = cached_power.decimal_exponent;
+  ASSERT((alpha <= c_mk->e() + e) && (c_mk->e() + e <= gamma));
+}
+#undef GRISU_REDUCTION
+#undef GRISU_CACHE_STRUCT
+#undef GRISU_CACHE_NAME
+#undef GRISU_CACHE_MAX_DISTANCE
+#undef GRISU_CACHE_OFFSET
+#undef GRISU_UINT64_C
+
+} }  // namespace v8::internal
+
+#endif  // V8_CACHED_POWERS_H_

src/checks.h

@@ -80,6 +80,7 @@ static inline void CheckEqualsHelper(const char* file, int line,
   }
 }
 
+
 // Helper function used by the CHECK_EQ function when given int64_t
 // arguments.  Should not be called directly.
 static inline void CheckEqualsHelper(const char* file, int line,
@@ -202,6 +203,27 @@ static inline void CheckEqualsHelper(const char* file,
 }
 
 
+static inline void CheckNonEqualsHelper(const char* file,
+                                     int line,
+                                     const char* expected_source,
+                                     double expected,
+                                     const char* value_source,
+                                     double value) {
+  // Force values to 64 bit memory to truncate 80 bit precision on IA32.
+  volatile double* exp = new double[1];
+  *exp = expected;
+  volatile double* val = new double[1];
+  *val = value;
+  if (*exp == *val) {
+    V8_Fatal(file, line,
+             "CHECK_NE(%s, %s) failed\n#   Value: %f",
+             expected_source, value_source, *val);
+  }
+  delete[] exp;
+  delete[] val;
+}
+
+
 namespace v8 {
   class Value;
   template <class T> class Handle;

src/conversions.cc

@@ -31,6 +31,7 @@
 
 #include "conversions-inl.h"
 #include "factory.h"
+#include "grisu3.h"
 #include "scanner.h"
 
 namespace v8 {
@@ -382,8 +383,17 @@ const char* DoubleToCString(double v, Vector<char> buffer) {
       int decimal_point;
       int sign;
 
-      char* decimal_rep = dtoa(v, 0, 0, &decimal_point, &sign, NULL);
-      int length = StrLength(decimal_rep);
+      char* decimal_rep;
+      bool used_dtoa = false;
+      char grisu_buffer[kGrisu3MaximalLength + 1];
+      int length;
+      if (grisu3(v, grisu_buffer, &sign, &length, &decimal_point)) {
+        decimal_rep = grisu_buffer;
+      } else {
+        decimal_rep = dtoa(v, 0, 0, &decimal_point, &sign, NULL);
+        used_dtoa = true;
+        length = StrLength(decimal_rep);
+      }
 
       if (sign) builder.AddCharacter('-');
 
@@ -418,7 +428,7 @@ const char* DoubleToCString(double v, Vector<char> buffer) {
         builder.AddFormatted("%d", exponent);
       }
 
-      freedtoa(decimal_rep);
+      if (used_dtoa) freedtoa(decimal_rep);
     }
   }
   return builder.Finalize();

src/diy_fp.h

+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
+// OWNER 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 V8_DIY_FP_H_
+#define V8_DIY_FP_H_
+
+namespace v8 {
+namespace internal {
+
+// This "Do It Yourself Floating Point" class implements a floating-point number
+// with a uint64 significand and an int exponent. Normalized DiyFp numbers will
+// have the most significant bit of the significand set.
+// Multiplication and Subtraction do not normalize their results.
+// DiyFp are not designed to contain special doubles (NaN and Infinity).
+class DiyFp {
+ public:
+  static const int kSignificandSize = 64;
+
+  DiyFp() : f_(0), e_(0) {}
+  DiyFp(uint64_t f, int e) : f_(f), e_(e) {}
+
+  // this = this - other.
+  // The exponents of both numbers must be the same and the significand of this
+  // must be bigger than the significand of other.
+  // The result will not be normalized.
+  void Subtract(const DiyFp& other) {
+    ASSERT(e_ == other.e_);
+    ASSERT(f_ >= other.f_);
+    f_ -= other.f_;
+  }
+
+  // Returns a - b.
+  // The exponents of both numbers must be the same and this must be bigger
+  // than other. The result will not be normalized.
+  static DiyFp Minus(const DiyFp& a, const DiyFp& b) {
+    DiyFp result = a;
+    result.Subtract(b);
+    return result;
+  }
+
+
+  // this = this * other.
+  void Multiply(const DiyFp& other) {
+    // Simply "emulates" a 128 bit multiplication.
+    // However: the resulting number only contains 64 bits. The least
+    // significant 64 bits are only used for rounding the most significant 64
+    // bits.
+    const uint64_t kM32 = 0xFFFFFFFFu;
+    uint64_t a = f_ >> 32;
+    uint64_t b = f_ & kM32;
+    uint64_t c = other.f_ >> 32;
+    uint64_t d = other.f_ & kM32;
+    uint64_t ac = a * c;
+    uint64_t bc = b * c;
+    uint64_t ad = a * d;
+    uint64_t bd = b * d;
+    uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);
+    tmp += 1U << 31;  // round
+    uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
+    e_ += other.e_ + 64;
+    f_ = result_f;
+  }
+
+  // returns a * b;
+  static DiyFp Times(const DiyFp& a, const DiyFp& b) {
+    DiyFp result = a;
+    result.Multiply(b);
+    return result;
+  }
+
+  void Normalize() {
+    ASSERT(f_ != 0);
+    uint64_t f = f_;
+    int e = e_;
+
+    // This method is mainly called for normalizing boundaries. In general
+    // boundaries need to be shifted by 10 bits. We thus optimize for this case.
+    const uint64_t k10MSBits = V8_2PART_UINT64_C(0xFFC00000, 00000000);
+    while ((f & k10MSBits) == 0) {
+      f <<= 10;
+      e -= 10;
+    }
+    while ((f & kUint64MSB) == 0) {
+      f <<= 1;
+      e--;
+    }
+    f_ = f;
+    e_ = e;
+  }
+
+  static DiyFp Normalize(const DiyFp& a) {
+    DiyFp result = a;
+    result.Normalize();
+    return result;
+  }
+
+  uint64_t f() const { return f_; }
+  int e() const { return e_; }
+
+  void set_f(uint64_t new_value) { f_ = new_value; }
+  void set_e(int new_value) { e_ = new_value; }
+
+ private:
+  static const uint64_t kUint64MSB = V8_2PART_UINT64_C(0x80000000, 00000000);
+
+  uint64_t f_;
+  int e_;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_DIY_FP_H_

src/double.h

+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
+// OWNER 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 V8_DOUBLE_H_
+#define V8_DOUBLE_H_
+
+#include "diy_fp.h"
+
+namespace v8 {
+namespace internal {
+
+// We assume that doubles and uint64_t have the same endianness.
+static uint64_t double_to_uint64(double d) { return bit_cast<uint64_t>(d); }
+static double uint64_to_double(uint64_t d64) { return bit_cast<double>(d64); }
+
+// Helper functions for doubles.
+class Double {
+ public:
+  static const uint64_t kSignMask = V8_2PART_UINT64_C(0x80000000, 00000000);
+  static const uint64_t kExponentMask = V8_2PART_UINT64_C(0x7FF00000, 00000000);
+  static const uint64_t kSignificandMask =
+      V8_2PART_UINT64_C(0x000FFFFF, FFFFFFFF);
+  static const uint64_t kHiddenBit = V8_2PART_UINT64_C(0x00100000, 00000000);
+
+  Double() : d64_(0) {}
+  explicit Double(double d) : d64_(double_to_uint64(d)) {}
+  explicit Double(uint64_t d64) : d64_(d64) {}
+
+  DiyFp AsDiyFp() const {
+    ASSERT(!IsSpecial());
+    return DiyFp(Significand(), Exponent());
+  }
+
+  // this->Significand() must not be 0.
+  DiyFp AsNormalizedDiyFp() const {
+    uint64_t f = Significand();
+    int e = Exponent();
+
+    ASSERT(f != 0);
+
+    // The current double could be a denormal.
+    while ((f & kHiddenBit) == 0) {
+      f <<= 1;
+      e--;
+    }
+    // Do the final shifts in one go. Don't forget the hidden bit (the '-1').
+    f <<= DiyFp::kSignificandSize - kSignificandSize - 1;
+    e -= DiyFp::kSignificandSize - kSignificandSize - 1;
+    return DiyFp(f, e);
+  }
+
+  // Returns the double's bit as uint64.
+  uint64_t AsUint64() const {
+    return d64_;
+  }
+
+  int Exponent() const {
+    if (IsDenormal()) return kDenormalExponent;
+
+    uint64_t d64 = AsUint64();
+    int biased_e = static_cast<int>((d64 & kExponentMask) >> kSignificandSize);
+    return biased_e - kExponentBias;
+  }
+
+  uint64_t Significand() const {
+    uint64_t d64 = AsUint64();
+    uint64_t significand = d64 & kSignificandMask;
+    if (!IsDenormal()) {
+      return significand + kHiddenBit;
+    } else {
+      return significand;
+    }
+  }
+
+  // Returns true if the double is a denormal.
+  bool IsDenormal() const {
+    uint64_t d64 = AsUint64();
+    return (d64 & kExponentMask) == 0;
+  }
+
+  // We consider denormals not to be special.
+  // Hence only Infinity and NaN are special.
+  bool IsSpecial() const {
+    uint64_t d64 = AsUint64();
+    return (d64 & kExponentMask) == kExponentMask;
+  }
+
+  bool IsNan() const {
+    uint64_t d64 = AsUint64();
+    return ((d64 & kExponentMask) == kExponentMask) &&
+        ((d64 & kSignificandMask) != 0);
+  }
+
+
+  bool IsInfinite() const {
+    uint64_t d64 = AsUint64();
+    return ((d64 & kExponentMask) == kExponentMask) &&
+        ((d64 & kSignificandMask) == 0);
+  }
+
+
+  int Sign() const {
+    uint64_t d64 = AsUint64();
+    return (d64 & kSignMask) == 0? 1: -1;
+  }
+
+
+  // Returns the two boundaries of this.
+  // The bigger boundary (m_plus) is normalized. The lower boundary has the same
+  // exponent as m_plus.
+  void NormalizedBoundaries(DiyFp* out_m_minus, DiyFp* out_m_plus) const {
+    DiyFp v = this->AsDiyFp();
+    bool significand_is_zero = (v.f() == kHiddenBit);
+    DiyFp m_plus = DiyFp::Normalize(DiyFp((v.f() << 1) + 1, v.e() - 1));
+    DiyFp m_minus;
+    if (significand_is_zero && v.e() != kDenormalExponent) {
+      // The boundary is closer. Think of v = 1000e10 and v- = 9999e9.
+      // Then the boundary (== (v - v-)/2) is not just at a distance of 1e9 but
+      // at a distance of 1e8.
+      // The only exception is for the smallest normal: the largest denormal is
+      // at the same distance as its successor.
+      // Note: denormals have the same exponent as the smallest normals.
+      m_minus = DiyFp((v.f() << 2) - 1, v.e() - 2);
+    } else {
+      m_minus = DiyFp((v.f() << 1) - 1, v.e() - 1);
+    }
+    m_minus.set_f(m_minus.f() << (m_minus.e() - m_plus.e()));
+    m_minus.set_e(m_plus.e());
+    *out_m_plus = m_plus;
+    *out_m_minus = m_minus;
+  }
+
+  double value() const { return uint64_to_double(d64_); }
+
+ private:
+  static const int kSignificandSize = 52;  // Excludes the hidden bit.
+  static const int kExponentBias = 0x3FF + kSignificandSize;
+  static const int kDenormalExponent = -kExponentBias + 1;
+
+  uint64_t d64_;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_DOUBLE_H_

src/globals.h

@@ -98,6 +98,11 @@ typedef byte* Address;
 #define V8_PTR_PREFIX ""
 #endif  // V8_HOST_ARCH_64_BIT
 
+// The following macro works on both 32 and 64-bit platforms.
+// Usage: instead of writing 0x1234567890123456
+//      write V8_2PART_UINT64_C(0x12345678,90123456);
+#define V8_2PART_UINT64_C(a, b) (((static_cast<uint64_t>(a) << 32) + 0x##b##u))
+
 #define V8PRIxPTR V8_PTR_PREFIX "x"
 #define V8PRIdPTR V8_PTR_PREFIX "d"
 

src/grisu3.h

+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
+// OWNER 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 V8_GRISU3_H_
+#define V8_GRISU3_H_
+
+namespace v8 {
+namespace internal {
+
+// Grisu3 will produce at most kGrisu3MaximalLength digits. This does not
+// include the terminating '\0' character.
+static const int kGrisu3MaximalLength = 17;
+
+// Provides a decimal representation of v.
+//   v must satisfy v != 0 and it must not be Infinity or NaN.
+// Returns true if it succeeds, otherwise the result can not be trusted.
+// There will be *length digits inside the buffer followed by a null terminator.
+// If the function returns true then
+//   v == (double) (buffer * 10^(decimal-point - length)).
+// The digits in the buffer are the shortest representation possible: no
+// 0.099999999999 instead of 0.1.
+// The last digit will be closest to the actual v. That is, even if several
+// digits might correctly yield 'v' when read again, the buffer will contain the
+// one closest to v.
+// The variable 'sign' will be '0' if the given number is positive, and '1'
+//   otherwise.
+bool grisu3(double d, char* buffer, int* sign, int* length, int* decimal_point);
+
+} }  // namespace v8::internal
+
+#endif  // V8_GRISU3_H_

test/cctest/SConscript

@@ -34,6 +34,7 @@ Import('context object_files')
 
 SOURCES = {
   'all': [
+    'gay_shortest.cc',
     'test-accessors.cc',
     'test-alloc.cc',
     'test-api.cc',
@@ -43,8 +44,11 @@ SOURCES = {
     'test-dataflow.cc',
     'test-debug.cc',
     'test-decls.cc',
+    'test-diy_fp.cc',
+    'test-double.cc',
     'test-flags.cc',
     'test-func-name-inference.cc',
+    'test-grisu3.cc',
     'test-hashmap.cc',
     'test-heap.cc',
     'test-heap-profiler.cc',

test/cctest/gay_shortest.h

+// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
+// OWNER 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 GAY_SHORTEST_H_
+#define GAY_SHORTEST_H_
+
+namespace v8 {
+namespace internal {
+
+struct GayShortest {
+  double v;
+  const char* representation;
+  int decimal_point;
+};
+
+Vector<const GayShortest> PrecomputedShortestRepresentations();
+
+} }  // namespace v8::internal
+
+#endif  // GAY_SHORTEST_H_

test/cctest/test-diy_fp.cc

+// Copyright 2006-2008 the V8 project authors. All rights reserved.
+
+#include <stdlib.h>
+
+#include "v8.h"
+
+#include "platform.h"
+#include "cctest.h"
+#include "diy_fp.h"
+
+
+using namespace v8::internal;
+
+
+TEST(Subtract) {
+  DiyFp diy_fp1 = DiyFp(3, 0);
+  DiyFp diy_fp2 = DiyFp(1, 0);
+  DiyFp diff = DiyFp::Minus(diy_fp1, diy_fp2);
+
+  CHECK(2 == diff.f());  // NOLINT
+  CHECK_EQ(0, diff.e());
+  diy_fp1.Subtract(diy_fp2);
+  CHECK(2 == diy_fp1.f());  // NOLINT
+  CHECK_EQ(0, diy_fp1.e());
+}
+
+
+TEST(Multiply) {
+  DiyFp diy_fp1 = DiyFp(3, 0);
+  DiyFp diy_fp2 = DiyFp(2, 0);
+  DiyFp product = DiyFp::Times(diy_fp1, diy_fp2);
+
+  CHECK(0 == product.f());  // NOLINT
+  CHECK_EQ(64, product.e());
+  diy_fp1.Multiply(diy_fp2);
+  CHECK(0 == diy_fp1.f());  // NOLINT
+  CHECK_EQ(64, diy_fp1.e());
+
+  diy_fp1 = DiyFp(V8_2PART_UINT64_C(0x80000000, 00000000), 11);
+  diy_fp2 = DiyFp(2, 13);
+  product = DiyFp::Times(diy_fp1, diy_fp2);
+  CHECK(1 == product.f());  // NOLINT
+  CHECK_EQ(11 + 13 + 64, product.e());
+
+  // Test rounding.
+  diy_fp1 = DiyFp(V8_2PART_UINT64_C(0x80000000, 00000001), 11);
+  diy_fp2 = DiyFp(1, 13);
+  product = DiyFp::Times(diy_fp1, diy_fp2);
+  CHECK(1 == product.f());  // NOLINT
+  CHECK_EQ(11 + 13 + 64, product.e());
+
+  diy_fp1 = DiyFp(V8_2PART_UINT64_C(0x7fffffff, ffffffff), 11);
+  diy_fp2 = DiyFp(1, 13);
+  product = DiyFp::Times(diy_fp1, diy_fp2);
+  CHECK(0 == product.f());  // NOLINT
+  CHECK_EQ(11 + 13 + 64, product.e());
+
+  // Halfway cases are allowed to round either way. So don't check for it.
+
+  // Big numbers.
+  diy_fp1 = DiyFp(V8_2PART_UINT64_C(0xFFFFFFFF, FFFFFFFF), 11);
+  diy_fp2 = DiyFp(V8_2PART_UINT64_C(0xFFFFFFFF, FFFFFFFF), 13);
+  // 128bit result: 0xfffffffffffffffe0000000000000001
+  product = DiyFp::Times(diy_fp1, diy_fp2);
+  CHECK(V8_2PART_UINT64_C(0xFFFFFFFF, FFFFFFFe) == product.f());
+  CHECK_EQ(11 + 13 + 64, product.e());
+}

test/cctest/test-double.cc

+// Copyright 2006-2008 the V8 project authors. All rights reserved.
+
+#include <stdlib.h>
+
+#include "v8.h"
+
+#include "platform.h"
+#include "cctest.h"
+#include "diy_fp.h"
+#include "double.h"
+
+
+using namespace v8::internal;
+
+
+TEST(Uint64Conversions) {
+  // Start by checking the byte-order.
+  uint64_t ordered = V8_2PART_UINT64_C(0x01234567, 89ABCDEF);
+  CHECK_EQ(3512700564088504e-318, Double(ordered).value());
+
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  CHECK_EQ(5e-324, Double(min_double64).value());
+
+  uint64_t max_double64 = V8_2PART_UINT64_C(0x7fefffff, ffffffff);
+  CHECK_EQ(1.7976931348623157e308, Double(max_double64).value());
+}
+
+TEST(AsDiyFp) {
+  uint64_t ordered = V8_2PART_UINT64_C(0x01234567, 89ABCDEF);
+  DiyFp diy_fp = Double(ordered).AsDiyFp();
+  CHECK_EQ(0x12 - 0x3FF - 52, diy_fp.e());
+  // The 52 mantissa bits, plus the implicit 1 in bit 52 as a UINT64.
+  CHECK(V8_2PART_UINT64_C(0x00134567, 89ABCDEF) == diy_fp.f());  // NOLINT
+
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  diy_fp = Double(min_double64).AsDiyFp();
+  CHECK_EQ(-0x3FF - 52 + 1, diy_fp.e());
+  // This is a denormal; so no hidden bit.
+  CHECK(1 == diy_fp.f());  // NOLINT
+
+  uint64_t max_double64 = V8_2PART_UINT64_C(0x7fefffff, ffffffff);
+  diy_fp = Double(max_double64).AsDiyFp();
+  CHECK_EQ(0x7FE - 0x3FF - 52, diy_fp.e());
+  CHECK(V8_2PART_UINT64_C(0x001fffff, ffffffff) == diy_fp.f());  // NOLINT
+}
+
+
+TEST(AsNormalizedDiyFp) {
+  uint64_t ordered = V8_2PART_UINT64_C(0x01234567, 89ABCDEF);
+  DiyFp diy_fp = Double(ordered).AsNormalizedDiyFp();
+  CHECK_EQ(0x12 - 0x3FF - 52 - 11, diy_fp.e());
+  CHECK((V8_2PART_UINT64_C(0x00134567, 89ABCDEF) << 11) ==
+        diy_fp.f());  // NOLINT
+
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  diy_fp = Double(min_double64).AsNormalizedDiyFp();
+  CHECK_EQ(-0x3FF - 52 + 1 - 63, diy_fp.e());
+  // This is a denormal; so no hidden bit.
+  CHECK(V8_2PART_UINT64_C(0x80000000, 00000000) == diy_fp.f());  // NOLINT
+
+  uint64_t max_double64 = V8_2PART_UINT64_C(0x7fefffff, ffffffff);
+  diy_fp = Double(max_double64).AsNormalizedDiyFp();
+  CHECK_EQ(0x7FE - 0x3FF - 52 - 11, diy_fp.e());
+  CHECK((V8_2PART_UINT64_C(0x001fffff, ffffffff) << 11) ==
+        diy_fp.f());  // NOLINT
+}
+
+
+TEST(IsDenormal) {
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  CHECK(Double(min_double64).IsDenormal());
+  uint64_t bits = V8_2PART_UINT64_C(0x000FFFFF, FFFFFFFF);
+  CHECK(Double(bits).IsDenormal());
+  bits = V8_2PART_UINT64_C(0x00100000, 00000000);
+  CHECK(!Double(bits).IsDenormal());
+}
+
+
+TEST(IsSpecial) {
+  CHECK(Double(V8_INFINITY).IsSpecial());
+  CHECK(Double(-V8_INFINITY).IsSpecial());
+  CHECK(Double(OS::nan_value()).IsSpecial());
+  uint64_t bits = V8_2PART_UINT64_C(0xFFF12345, 00000000);
+  CHECK(Double(bits).IsSpecial());
+  // Denormals are not special:
+  CHECK(!Double(5e-324).IsSpecial());
+  CHECK(!Double(-5e-324).IsSpecial());
+  // And some random numbers:
+  CHECK(!Double(0.0).IsSpecial());
+  CHECK(!Double(-0.0).IsSpecial());
+  CHECK(!Double(1.0).IsSpecial());
+  CHECK(!Double(-1.0).IsSpecial());
+  CHECK(!Double(1000000.0).IsSpecial());
+  CHECK(!Double(-1000000.0).IsSpecial());
+  CHECK(!Double(1e23).IsSpecial());
+  CHECK(!Double(-1e23).IsSpecial());
+  CHECK(!Double(1.7976931348623157e308).IsSpecial());
+  CHECK(!Double(-1.7976931348623157e308).IsSpecial());
+}
+
+
+TEST(IsInfinite) {
+  CHECK(Double(V8_INFINITY).IsInfinite());
+  CHECK(Double(-V8_INFINITY).IsInfinite());
+  CHECK(!Double(OS::nan_value()).IsInfinite());
+  CHECK(!Double(0.0).IsInfinite());
+  CHECK(!Double(-0.0).IsInfinite());
+  CHECK(!Double(1.0).IsInfinite());
+  CHECK(!Double(-1.0).IsInfinite());
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  CHECK(!Double(min_double64).IsInfinite());
+}
+
+
+TEST(IsNan) {
+  CHECK(Double(OS::nan_value()).IsNan());
+  uint64_t other_nan = V8_2PART_UINT64_C(0xFFFFFFFF, 00000001);
+  CHECK(Double(other_nan).IsNan());
+  CHECK(!Double(V8_INFINITY).IsNan());
+  CHECK(!Double(-V8_INFINITY).IsNan());
+  CHECK(!Double(0.0).IsNan());
+  CHECK(!Double(-0.0).IsNan());
+  CHECK(!Double(1.0).IsNan());
+  CHECK(!Double(-1.0).IsNan());
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  CHECK(!Double(min_double64).IsNan());
+}
+
+
+TEST(Sign) {
+  CHECK_EQ(1, Double(1.0).Sign());
+  CHECK_EQ(1, Double(V8_INFINITY).Sign());
+  CHECK_EQ(-1, Double(-V8_INFINITY).Sign());
+  CHECK_EQ(1, Double(0.0).Sign());
+  CHECK_EQ(-1, Double(-0.0).Sign());
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  CHECK_EQ(1, Double(min_double64).Sign());
+}
+
+
+TEST(NormalizedBoundaries) {
+  DiyFp boundary_plus;
+  DiyFp boundary_minus;
+  DiyFp diy_fp = Double(1.5).AsNormalizedDiyFp();
+  Double(1.5).NormalizedBoundaries(&boundary_minus, &boundary_plus);
+  CHECK_EQ(diy_fp.e(), boundary_minus.e());
+  CHECK_EQ(diy_fp.e(), boundary_plus.e());
+  // 1.5 does not have a significand of the form 2^p (for some p).
+  // Therefore its boundaries are at the same distance.
+  CHECK(diy_fp.f() - boundary_minus.f() == boundary_plus.f() - diy_fp.f());
+  CHECK((1 << 10) == diy_fp.f() - boundary_minus.f());  // NOLINT
+
+  diy_fp = Double(1.0).AsNormalizedDiyFp();
+  Double(1.0).NormalizedBoundaries(&boundary_minus, &boundary_plus);
+  CHECK_EQ(diy_fp.e(), boundary_minus.e());
+  CHECK_EQ(diy_fp.e(), boundary_plus.e());
+  // 1.0 does have a significand of the form 2^p (for some p).
+  // Therefore its lower boundary is twice as close as the upper boundary.
+  CHECK_GT(boundary_plus.f() - diy_fp.f(), diy_fp.f() - boundary_minus.f());
+  CHECK((1 << 9) == diy_fp.f() - boundary_minus.f());  // NOLINT
+  CHECK((1 << 10) == boundary_plus.f() - diy_fp.f());  // NOLINT
+
+  uint64_t min_double64 = V8_2PART_UINT64_C(0x00000000, 00000001);
+  diy_fp = Double(min_double64).AsNormalizedDiyFp();
+  Double(min_double64).NormalizedBoundaries(&boundary_minus, &boundary_plus);
+  CHECK_EQ(diy_fp.e(), boundary_minus.e());
+  CHECK_EQ(diy_fp.e(), boundary_plus.e());
+  // min-value does not have a significand of the form 2^p (for some p).
+  // Therefore its boundaries are at the same distance.
+  CHECK(diy_fp.f() - boundary_minus.f() == boundary_plus.f() - diy_fp.f());
+  // Denormals have their boundaries much closer.
+  CHECK((static_cast<uint64_t>(1) << 62) ==
+        diy_fp.f() - boundary_minus.f());  // NOLINT
+
+  uint64_t smallest_normal64 = V8_2PART_UINT64_C(0x00100000, 00000000);
+  diy_fp = Double(smallest_normal64).AsNormalizedDiyFp();
+  Double(smallest_normal64).NormalizedBoundaries(&boundary_minus,
+                                                 &boundary_plus);
+  CHECK_EQ(diy_fp.e(), boundary_minus.e());
+  CHECK_EQ(diy_fp.e(), boundary_plus.e());
+  // Even though the significand is of the form 2^p (for some p), its boundaries
+  // are at the same distance. (This is the only exception).
+  CHECK(diy_fp.f() - boundary_minus.f() == boundary_plus.f() - diy_fp.f());
+  CHECK((1 << 10) == diy_fp.f() - boundary_minus.f());  // NOLINT
+
+  uint64_t largest_denormal64 = V8_2PART_UINT64_C(0x000FFFFF, FFFFFFFF);
+  diy_fp = Double(largest_denormal64).AsNormalizedDiyFp();
+  Double(largest_denormal64).NormalizedBoundaries(&boundary_minus,
+                                                  &boundary_plus);
+  CHECK_EQ(diy_fp.e(), boundary_minus.e());
+  CHECK_EQ(diy_fp.e(), boundary_plus.e());
+  CHECK(diy_fp.f() - boundary_minus.f() == boundary_plus.f() - diy_fp.f());
+  CHECK((1 << 11) == diy_fp.f() - boundary_minus.f());  // NOLINT
+
+  uint64_t max_double64 = V8_2PART_UINT64_C(0x7fefffff, ffffffff);
+  diy_fp = Double(max_double64).AsNormalizedDiyFp();
+  Double(max_double64).NormalizedBoundaries(&boundary_minus, &boundary_plus);
+  CHECK_EQ(diy_fp.e(), boundary_minus.e());
+  CHECK_EQ(diy_fp.e(), boundary_plus.e());
+  // max-value does not have a significand of the form 2^p (for some p).
+  // Therefore its boundaries are at the same distance.
+  CHECK(diy_fp.f() - boundary_minus.f() == boundary_plus.f() - diy_fp.f());
+  CHECK((1 << 10) == diy_fp.f() - boundary_minus.f());  // NOLINT
+}

test/cctest/test-grisu3.cc

+// Copyright 2006-2008 the V8 project authors. All rights reserved.
+
+#include <stdlib.h>
+
+#include "v8.h"
+
+#include "platform.h"
+#include "cctest.h"
+#include "diy_fp.h"
+#include "double.h"
+#include "gay_shortest.h"
+#include "grisu3.h"
+
+using namespace v8::internal;
+
+static const int kBufferSize = 100;
+
+TEST(GrisuVariousDoubles) {
+  char buffer[kBufferSize];
+  int sign;
+  int length;
+  int point;
+  int status;
+
+  double min_double = 5e-324;
+  status = grisu3(min_double, buffer, &sign, &length, &point);
+  CHECK(status);
+  CHECK_EQ(0, sign);
+  CHECK_EQ("5", buffer);
+  CHECK_EQ(-323, point);
+
+  double max_double = 1.7976931348623157e308;
+  status = grisu3(max_double, buffer, &sign, &length, &point);
+  CHECK(status);
+  CHECK_EQ(0, sign);
+  CHECK_EQ("17976931348623157", buffer);
+  CHECK_EQ(309, point);
+
+  status = grisu3(4294967272.0, buffer, &sign, &length, &point);
+  CHECK(status);
+  CHECK_EQ(0, sign);
+  CHECK_EQ("4294967272", buffer);
+  CHECK_EQ(10, point);
+
+  status = grisu3(4.1855804968213567e298, buffer, &sign, &length, &point);
+  CHECK(status);
+  CHECK_EQ(0, sign);
+  CHECK_EQ("4185580496821357", buffer);
+  CHECK_EQ(299, point);
+
+  status = grisu3(5.5626846462680035e-309, buffer, &sign, &length, &point);
+  CHECK(status);
+  CHECK_EQ(0, sign);
+  CHECK_EQ("5562684646268003", buffer);
+  CHECK_EQ(-308, point);
+
+  status = grisu3(2147483648.0, buffer, &sign, &length, &point);
+  CHECK(status);
+  CHECK_EQ(0, sign);
+  CHECK_EQ("2147483648", buffer);
+  CHECK_EQ(10, point);
+
+  status = grisu3(3.5844466002796428e+298, buffer, &sign, &length, &point);
+  if (status) {  // Not all grisu3 variants manage to compute this number.
+    CHECK_EQ("35844466002796428", buffer);
+    CHECK_EQ(0, sign);
+    CHECK_EQ(299, point);
+  }
+
+  uint64_t smallest_normal64 = V8_2PART_UINT64_C(0x00100000, 00000000);
+  double v = Double(smallest_normal64).value();
+  status = grisu3(v, buffer, &sign, &length, &point);
+  if (status) {
+    CHECK_EQ(0, sign);
+    CHECK_EQ("22250738585072014", buffer);
+    CHECK_EQ(-307, point);
+  }
+
+  uint64_t largest_denormal64 = V8_2PART_UINT64_C(0x000FFFFF, FFFFFFFF);
+  v = Double(largest_denormal64).value();
+  status = grisu3(v, buffer, &sign, &length, &point);
+  if (status) {
+    CHECK_EQ(0, sign);
+    CHECK_EQ("2225073858507201", buffer);
+    CHECK_EQ(-307, point);
+  }
+}
+
+
+TEST(GrisuGayShortest) {
+  char buffer[kBufferSize];
+  bool status;
+  int sign;
+  int length;
+  int point;
+  int succeeded = 0;
+  int total = 0;
+  bool needed_max_length = false;
+
+  Vector<const GayShortest> precomputed = PrecomputedShortestRepresentations();
+  for (int i = 0; i < precomputed.length(); ++i) {
+    const GayShortest current_test = precomputed[i];
+    total++;
+    double v = current_test.v;
+    status = grisu3(v, buffer, &sign, &length, &point);
+    CHECK_GE(kGrisu3MaximalLength, length);
+    if (!status) continue;
+    if (length == kGrisu3MaximalLength) needed_max_length = true;
+    succeeded++;
+    CHECK_EQ(0, sign);  // All precomputed numbers are positive.
+    CHECK_EQ(current_test.decimal_point, point);
+    CHECK_EQ(current_test.representation, buffer);
+  }
+  CHECK_GT(succeeded*1.0/total, 0.99);
+  CHECK(needed_max_length);
+}

tools/gyp/v8.gyp

@@ -229,6 +229,7 @@
         '../../src/builtins.cc',
         '../../src/builtins.h',
         '../../src/bytecodes-irregexp.h',
+        '../../src/cached_powers.h',
         '../../src/char-predicates-inl.h',
         '../../src/char-predicates.h',
         '../../src/checks.cc',
@@ -264,6 +265,8 @@
         '../../src/disassembler.cc',
         '../../src/disassembler.h',
         '../../src/dtoa-config.c',
+        '../../src/diy_fp.h',
+        '../../src/double.h',
         '../../src/execution.cc',
         '../../src/execution.h',
         '../../src/factory.cc',
@@ -284,6 +287,8 @@
         '../../src/global-handles.cc',
         '../../src/global-handles.h',
         '../../src/globals.h',
+        '../../src/grisu3.h',
+        '../../src/grisu3.cc',
         '../../src/handles-inl.h',
         '../../src/handles.cc',
         '../../src/handles.h',
@@ -330,6 +335,7 @@
         '../../src/parser.cc',
         '../../src/parser.h',
         '../../src/platform.h',
+        '../../src/powers_ten.h',
         '../../src/prettyprinter.cc',
         '../../src/prettyprinter.h',
         '../../src/property.cc',