Add bignum fall-back when the fast dtoa doesn't succeed. This removes Gay's...

Add bignum fall-back when the fast dtoa doesn't succeed. This removes Gay's dtoa for the double->string direction. We still need it for the string->double direction.
Review URL: http://codereview.chromium.org/3468003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5840 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/SConscript

@@ -41,6 +41,7 @@ SOURCES = {
     assembler.cc
     ast.cc
     bignum.cc
+    bignum-dtoa.cc
     bootstrapper.cc
     builtins.cc
     cached-powers.cc

src/bignum-dtoa.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_BIGNUM_DTOA_H_
+#define V8_BIGNUM_DTOA_H_
+
+namespace v8 {
+namespace internal {
+
+enum BignumDtoaMode {
+  // Return the shortest correct representation.
+  // For example the output of 0.299999999999999988897 is (the less accurate but
+  // correct) 0.3.
+  BIGNUM_DTOA_SHORTEST,
+  // Return a fixed number of digits after the decimal point.
+  // For instance fixed(0.1, 4) becomes 0.1000
+  // If the input number is big, the output will be big.
+  BIGNUM_DTOA_FIXED,
+  // Return a fixed number of digits, no matter what the exponent is.
+  BIGNUM_DTOA_PRECISION
+};
+
+// Converts the given double 'v' to ascii.
+// The result should be interpreted as buffer * 10^(point-length).
+// The buffer will be null-terminated.
+//
+// The input v must be > 0 and different from NaN, and Infinity.
+//
+// The output depends on the given mode:
+//  - SHORTEST: produce the least amount of digits for which the internal
+//   identity requirement is still satisfied. If the digits are printed
+//   (together with the correct exponent) then reading this number will give
+//   'v' again. The buffer will choose the representation that is closest to
+//   'v'. If there are two at the same distance, than the number is round up.
+//   In this mode the 'requested_digits' parameter is ignored.
+//  - FIXED: produces digits necessary to print a given number with
+//   'requested_digits' digits after the decimal point. The produced digits
+//   might be too short in which case the caller has to fill the gaps with '0's.
+//   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
+//   Halfway cases are rounded up. The call toFixed(0.15, 2) thus returns
+//     buffer="2", point=0.
+//   Note: the length of the returned buffer has no meaning wrt the significance
+//   of its digits. That is, just because it contains '0's does not mean that
+//   any other digit would not satisfy the internal identity requirement.
+//  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
+//   Even though the length of produced digits usually equals
+//   'requested_digits', the function is allowed to return fewer digits, in
+//   which case the caller has to fill the missing digits with '0's.
+//   Halfway cases are again rounded up.
+// 'BignumDtoa' expects the given buffer to be big enough to hold all digits
+// and a terminating null-character.
+void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
+                Vector<char> buffer, int* length, int* point);
+
+} }  // namespace v8::internal
+
+#endif  // V8_BIGNUM_DTOA_H_

src/conversions.cc

@@ -654,7 +654,7 @@ static double InternalStringToDouble(Iterator current,
   buffer[buffer_pos] = '\0';
 
   double converted = Strtod(Vector<const char>(buffer, buffer_pos), exponent);
-  return sign? -converted: converted;
+  return sign ? -converted : converted;
 }
 
 
@@ -711,11 +711,6 @@ double StringToDouble(Vector<const char> str,
 }
 
 
-extern "C" char* dtoa(double d, int mode, int ndigits,
-                      int* decpt, int* sign, char** rve);
-
-extern "C" void freedtoa(char* s);
-
 const char* DoubleToCString(double v, Vector<char> buffer) {
   StringBuilder builder(buffer.start(), buffer.length());
 
@@ -739,21 +734,13 @@ const char* DoubleToCString(double v, Vector<char> buffer) {
     default: {
       int decimal_point;
       int sign;
-      char* decimal_rep;
-      bool used_gay_dtoa = false;
       const int kV8DtoaBufferCapacity = kBase10MaximalLength + 1;
-      char v8_dtoa_buffer[kV8DtoaBufferCapacity];
+      char decimal_rep[kV8DtoaBufferCapacity];
       int length;
 
-      if (DoubleToAscii(v, DTOA_SHORTEST, 0,
-                        Vector<char>(v8_dtoa_buffer, kV8DtoaBufferCapacity),
-                        &sign, &length, &decimal_point)) {
-        decimal_rep = v8_dtoa_buffer;
-      } else {
-        decimal_rep = dtoa(v, 0, 0, &decimal_point, &sign, NULL);
-        used_gay_dtoa = true;
-        length = StrLength(decimal_rep);
-      }
+      DoubleToAscii(v, DTOA_SHORTEST, 0,
+                    Vector<char>(decimal_rep, kV8DtoaBufferCapacity),
+                    &sign, &length, &decimal_point);
 
       if (sign) builder.AddCharacter('-');
 
@@ -787,8 +774,6 @@ const char* DoubleToCString(double v, Vector<char> buffer) {
         if (exponent < 0) exponent = -exponent;
         builder.AddFormatted("%d", exponent);
       }
-
-      if (used_gay_dtoa) freedtoa(decimal_rep);
     }
   }
   return builder.Finalize();
@@ -845,11 +830,9 @@ char* DoubleToFixedCString(double value, int f) {
       kMaxDigitsBeforePoint + kMaxDigitsAfterPoint + 1;
   char decimal_rep[kDecimalRepCapacity];
   int decimal_rep_length;
-  bool status = DoubleToAscii(value, DTOA_FIXED, f,
-                              Vector<char>(decimal_rep, kDecimalRepCapacity),
-                              &sign, &decimal_rep_length, &decimal_point);
-  USE(status);
-  ASSERT(status);
+  DoubleToAscii(value, DTOA_FIXED, f,
+                Vector<char>(decimal_rep, kDecimalRepCapacity),
+                &sign, &decimal_rep_length, &decimal_point);
 
   // Create a representation that is padded with zeros if needed.
   int zero_prefix_length = 0;
@@ -935,8 +918,6 @@ char* DoubleToExponentialCString(double value, int f) {
   // Find a sufficiently precise decimal representation of n.
   int decimal_point;
   int sign;
-  char* decimal_rep = NULL;
-  bool used_gay_dtoa = false;
   // f corresponds to the digits after the point. There is always one digit
   // before the point. The number of requested_digits equals hence f + 1.
   // And we have to add one character for the null-terminator.
@@ -944,31 +925,18 @@ char* DoubleToExponentialCString(double value, int f) {
   // Make sure that the buffer is big enough, even if we fall back to the
   // shortest representation (which happens when f equals -1).
   ASSERT(kBase10MaximalLength <= kMaxDigitsAfterPoint + 1);
-  char v8_dtoa_buffer[kV8DtoaBufferCapacity];
+  char decimal_rep[kV8DtoaBufferCapacity];
   int decimal_rep_length;
 
   if (f == -1) {
-    if (DoubleToAscii(value, DTOA_SHORTEST, 0,
-                      Vector<char>(v8_dtoa_buffer, kV8DtoaBufferCapacity),
-                      &sign, &decimal_rep_length, &decimal_point)) {
-      f = decimal_rep_length - 1;
-      decimal_rep = v8_dtoa_buffer;
-    } else {
-      decimal_rep = dtoa(value, 0, 0, &decimal_point, &sign, NULL);
-      decimal_rep_length = StrLength(decimal_rep);
-      f = decimal_rep_length - 1;
-      used_gay_dtoa = true;
-    }
+    DoubleToAscii(value, DTOA_SHORTEST, 0,
+                  Vector<char>(decimal_rep, kV8DtoaBufferCapacity),
+                  &sign, &decimal_rep_length, &decimal_point);
+    f = decimal_rep_length - 1;
   } else {
-    if (DoubleToAscii(value, DTOA_PRECISION, f + 1,
-                      Vector<char>(v8_dtoa_buffer, kV8DtoaBufferCapacity),
-                      &sign, &decimal_rep_length, &decimal_point)) {
-      decimal_rep = v8_dtoa_buffer;
-    } else {
-      decimal_rep = dtoa(value, 2, f + 1, &decimal_point, &sign, NULL);
-      decimal_rep_length = StrLength(decimal_rep);
-      used_gay_dtoa = true;
-    }
+    DoubleToAscii(value, DTOA_PRECISION, f + 1,
+                  Vector<char>(decimal_rep, kV8DtoaBufferCapacity),
+                  &sign, &decimal_rep_length, &decimal_point);
   }
   ASSERT(decimal_rep_length > 0);
   ASSERT(decimal_rep_length <= f + 1);
@@ -977,10 +945,6 @@ char* DoubleToExponentialCString(double value, int f) {
   char* result =
       CreateExponentialRepresentation(decimal_rep, exponent, negative, f+1);
 
-  if (used_gay_dtoa) {
-    freedtoa(decimal_rep);
-  }
-
   return result;
 }
 
@@ -1000,22 +964,14 @@ char* DoubleToPrecisionCString(double value, int p) {
   // Find a sufficiently precise decimal representation of n.
   int decimal_point;
   int sign;
-  char* decimal_rep = NULL;
-  bool used_gay_dtoa = false;
   // Add one for the terminating null character.
   const int kV8DtoaBufferCapacity = kMaximalDigits + 1;
-  char v8_dtoa_buffer[kV8DtoaBufferCapacity];
+  char decimal_rep[kV8DtoaBufferCapacity];
   int decimal_rep_length;
 
-  if (DoubleToAscii(value, DTOA_PRECISION, p,
-                    Vector<char>(v8_dtoa_buffer, kV8DtoaBufferCapacity),
-                    &sign, &decimal_rep_length, &decimal_point)) {
-    decimal_rep = v8_dtoa_buffer;
-  } else {
-    decimal_rep = dtoa(value, 2, p, &decimal_point, &sign, NULL);
-    decimal_rep_length = StrLength(decimal_rep);
-    used_gay_dtoa = true;
-  }
+  DoubleToAscii(value, DTOA_PRECISION, p,
+                Vector<char>(decimal_rep, kV8DtoaBufferCapacity),
+                &sign, &decimal_rep_length, &decimal_point);
   ASSERT(decimal_rep_length <= p);
 
   int exponent = decimal_point - 1;
@@ -1059,9 +1015,6 @@ char* DoubleToPrecisionCString(double value, int p) {
     result = builder.Finalize();
   }
 
-  if (used_gay_dtoa) {
-    freedtoa(decimal_rep);
-  }
   return result;
 }
 

src/dtoa.cc

@@ -30,6 +30,7 @@
 #include "v8.h"
 #include "dtoa.h"
 
+#include "bignum-dtoa.h"
 #include "double.h"
 #include "fast-dtoa.h"
 #include "fixed-dtoa.h"
@@ -37,7 +38,19 @@
 namespace v8 {
 namespace internal {
 
-bool DoubleToAscii(double v, DtoaMode mode, int requested_digits,
+static BignumDtoaMode DtoaToBignumDtoaMode(DtoaMode dtoa_mode) {
+  switch (dtoa_mode) {
+    case DTOA_SHORTEST:  return BIGNUM_DTOA_SHORTEST;
+    case DTOA_FIXED:     return BIGNUM_DTOA_FIXED;
+    case DTOA_PRECISION: return BIGNUM_DTOA_PRECISION;
+    default:
+      UNREACHABLE();
+      return BIGNUM_DTOA_SHORTEST;  // To silence compiler.
+  }
+}
+
+
+void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
                    Vector<char> buffer, int* sign, int* length, int* point) {
   ASSERT(!Double(v).IsSpecial());
   ASSERT(mode == DTOA_SHORTEST || requested_digits >= 0);
@@ -54,25 +67,37 @@ bool DoubleToAscii(double v, DtoaMode mode, int requested_digits,
     buffer[1] = '\0';
     *length = 1;
     *point = 1;
-    return true;
+    return;
   }
 
   if (mode == DTOA_PRECISION && requested_digits == 0) {
     buffer[0] = '\0';
     *length = 0;
-    return true;
+    return;
   }
 
+  bool fast_worked;
   switch (mode) {
     case DTOA_SHORTEST:
-      return FastDtoa(v, FAST_DTOA_SHORTEST, 0, buffer, length, point);
+      fast_worked = FastDtoa(v, FAST_DTOA_SHORTEST, 0, buffer, length, point);
+      break;
     case DTOA_FIXED:
-      return FastFixedDtoa(v, requested_digits, buffer, length, point);
+      fast_worked = FastFixedDtoa(v, requested_digits, buffer, length, point);
+      break;
     case DTOA_PRECISION:
-      return FastDtoa(v, FAST_DTOA_PRECISION, requested_digits,
-                      buffer, length, point);
+      fast_worked = FastDtoa(v, FAST_DTOA_PRECISION, requested_digits,
+                             buffer, length, point);
+      break;
+    default:
+      UNREACHABLE();
+      fast_worked = false;
   }
-  return false;
+  if (fast_worked) return;
+
+  // If the fast dtoa didn't succeed use the slower bignum version.
+  BignumDtoaMode bignum_mode = DtoaToBignumDtoaMode(mode);
+  BignumDtoa(v, bignum_mode, requested_digits, buffer, length, point);
+  buffer[*length] = '\0';
 }
 
 } }  // namespace v8::internal

src/dtoa.h

@@ -32,13 +32,15 @@ namespace v8 {
 namespace internal {
 
 enum DtoaMode {
-  // 0.9999999999999999 becomes 0.1
+  // Return the shortest correct representation.
+  // For example the output of 0.299999999999999988897 is (the less accurate but
+  // correct) 0.3.
   DTOA_SHORTEST,
-  // Fixed number of digits after the decimal point.
+  // Return a fixed number of digits after the decimal point.
   // For instance fixed(0.1, 4) becomes 0.1000
   // If the input number is big, the output will be big.
   DTOA_FIXED,
-  // Fixed number of digits (independent of the decimal point).
+  // Return a fixed number of digits, no matter what the exponent is.
   DTOA_PRECISION
 };
 
@@ -72,8 +74,10 @@ static const int kBase10MaximalLength = 17;
 //   which case the caller has to fill the missing digits with '0's.
 //   Halfway cases are again rounded away from 0.
 // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
-// and a terminating null-character.
-bool DoubleToAscii(double v, DtoaMode mode, int requested_digits,
+// and a terminating null-character. In SHORTEST-mode it expects a buffer of
+// at least kBase10MaximalLength + 1. Otherwise, the size of the output is
+// limited to requested_digits digits plus the null terminator.
+void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
                    Vector<char> buffer, int* sign, int* length, int* point);
 
 } }  // namespace v8::internal

test/cctest/SConscript

@@ -42,6 +42,7 @@ SOURCES = {
     'test-api.cc',
     'test-ast.cc',
     'test-bignum.cc',
+    'test-bignum-dtoa.cc',
     'test-circular-queue.cc',
     'test-compiler.cc',
     'test-conversions.cc',
@@ -51,6 +52,7 @@ SOURCES = {
     'test-decls.cc',
     'test-diy-fp.cc',
     'test-double.cc',
+    'test-dtoa.cc',
     'test-fast-dtoa.cc',
     'test-fixed-dtoa.cc',
     'test-flags.cc',

tools/gyp/v8.gyp

@@ -282,6 +282,8 @@
         '../../src/ast.h',
         '../../src/bignum.cc',
         '../../src/bignum.h',
+        '../../src/bignum-dtoa.cc',
+        '../../src/bignum-dtoa.h',
         '../../src/bootstrapper.cc',
         '../../src/bootstrapper.h',
         '../../src/builtins.cc',