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| 1 // Copyright 2014 the V8 project authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include "src/v8.h" |
| 6 |
| 7 #include "src/arguments.h" |
| 8 #include "src/codegen.h" |
| 9 #include "src/misc-intrinsics.h" |
| 10 #include "src/runtime/runtime.h" |
| 11 #include "src/runtime/runtime-utils.h" |
| 12 |
| 13 |
| 14 #ifndef _STLP_VENDOR_CSTD |
| 15 // STLPort doesn't import fpclassify and isless into the std namespace. |
| 16 using std::fpclassify; |
| 17 using std::isless; |
| 18 #endif |
| 19 |
| 20 namespace v8 { |
| 21 namespace internal { |
| 22 |
| 23 RUNTIME_FUNCTION(Runtime_NumberToRadixString) { |
| 24 HandleScope scope(isolate); |
| 25 DCHECK(args.length() == 2); |
| 26 CONVERT_SMI_ARG_CHECKED(radix, 1); |
| 27 RUNTIME_ASSERT(2 <= radix && radix <= 36); |
| 28 |
| 29 // Fast case where the result is a one character string. |
| 30 if (args[0]->IsSmi()) { |
| 31 int value = args.smi_at(0); |
| 32 if (value >= 0 && value < radix) { |
| 33 // Character array used for conversion. |
| 34 static const char kCharTable[] = "0123456789abcdefghijklmnopqrstuvwxyz"; |
| 35 return *isolate->factory()->LookupSingleCharacterStringFromCode( |
| 36 kCharTable[value]); |
| 37 } |
| 38 } |
| 39 |
| 40 // Slow case. |
| 41 CONVERT_DOUBLE_ARG_CHECKED(value, 0); |
| 42 if (std::isnan(value)) { |
| 43 return isolate->heap()->nan_string(); |
| 44 } |
| 45 if (std::isinf(value)) { |
| 46 if (value < 0) { |
| 47 return isolate->heap()->minus_infinity_string(); |
| 48 } |
| 49 return isolate->heap()->infinity_string(); |
| 50 } |
| 51 char* str = DoubleToRadixCString(value, radix); |
| 52 Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str); |
| 53 DeleteArray(str); |
| 54 return *result; |
| 55 } |
| 56 |
| 57 |
| 58 RUNTIME_FUNCTION(Runtime_NumberToFixed) { |
| 59 HandleScope scope(isolate); |
| 60 DCHECK(args.length() == 2); |
| 61 |
| 62 CONVERT_DOUBLE_ARG_CHECKED(value, 0); |
| 63 CONVERT_DOUBLE_ARG_CHECKED(f_number, 1); |
| 64 int f = FastD2IChecked(f_number); |
| 65 // See DoubleToFixedCString for these constants: |
| 66 RUNTIME_ASSERT(f >= 0 && f <= 20); |
| 67 RUNTIME_ASSERT(!Double(value).IsSpecial()); |
| 68 char* str = DoubleToFixedCString(value, f); |
| 69 Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str); |
| 70 DeleteArray(str); |
| 71 return *result; |
| 72 } |
| 73 |
| 74 |
| 75 RUNTIME_FUNCTION(Runtime_NumberToExponential) { |
| 76 HandleScope scope(isolate); |
| 77 DCHECK(args.length() == 2); |
| 78 |
| 79 CONVERT_DOUBLE_ARG_CHECKED(value, 0); |
| 80 CONVERT_DOUBLE_ARG_CHECKED(f_number, 1); |
| 81 int f = FastD2IChecked(f_number); |
| 82 RUNTIME_ASSERT(f >= -1 && f <= 20); |
| 83 RUNTIME_ASSERT(!Double(value).IsSpecial()); |
| 84 char* str = DoubleToExponentialCString(value, f); |
| 85 Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str); |
| 86 DeleteArray(str); |
| 87 return *result; |
| 88 } |
| 89 |
| 90 |
| 91 RUNTIME_FUNCTION(Runtime_NumberToPrecision) { |
| 92 HandleScope scope(isolate); |
| 93 DCHECK(args.length() == 2); |
| 94 |
| 95 CONVERT_DOUBLE_ARG_CHECKED(value, 0); |
| 96 CONVERT_DOUBLE_ARG_CHECKED(f_number, 1); |
| 97 int f = FastD2IChecked(f_number); |
| 98 RUNTIME_ASSERT(f >= 1 && f <= 21); |
| 99 RUNTIME_ASSERT(!Double(value).IsSpecial()); |
| 100 char* str = DoubleToPrecisionCString(value, f); |
| 101 Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str); |
| 102 DeleteArray(str); |
| 103 return *result; |
| 104 } |
| 105 |
| 106 |
| 107 RUNTIME_FUNCTION(Runtime_IsValidSmi) { |
| 108 SealHandleScope shs(isolate); |
| 109 DCHECK(args.length() == 1); |
| 110 |
| 111 CONVERT_NUMBER_CHECKED(int32_t, number, Int32, args[0]); |
| 112 return isolate->heap()->ToBoolean(Smi::IsValid(number)); |
| 113 } |
| 114 |
| 115 |
| 116 static bool AreDigits(const uint8_t* s, int from, int to) { |
| 117 for (int i = from; i < to; i++) { |
| 118 if (s[i] < '0' || s[i] > '9') return false; |
| 119 } |
| 120 |
| 121 return true; |
| 122 } |
| 123 |
| 124 |
| 125 static int ParseDecimalInteger(const uint8_t* s, int from, int to) { |
| 126 DCHECK(to - from < 10); // Overflow is not possible. |
| 127 DCHECK(from < to); |
| 128 int d = s[from] - '0'; |
| 129 |
| 130 for (int i = from + 1; i < to; i++) { |
| 131 d = 10 * d + (s[i] - '0'); |
| 132 } |
| 133 |
| 134 return d; |
| 135 } |
| 136 |
| 137 |
| 138 RUNTIME_FUNCTION(Runtime_StringToNumber) { |
| 139 HandleScope handle_scope(isolate); |
| 140 DCHECK(args.length() == 1); |
| 141 CONVERT_ARG_HANDLE_CHECKED(String, subject, 0); |
| 142 subject = String::Flatten(subject); |
| 143 |
| 144 // Fast case: short integer or some sorts of junk values. |
| 145 if (subject->IsSeqOneByteString()) { |
| 146 int len = subject->length(); |
| 147 if (len == 0) return Smi::FromInt(0); |
| 148 |
| 149 DisallowHeapAllocation no_gc; |
| 150 uint8_t const* data = Handle<SeqOneByteString>::cast(subject)->GetChars(); |
| 151 bool minus = (data[0] == '-'); |
| 152 int start_pos = (minus ? 1 : 0); |
| 153 |
| 154 if (start_pos == len) { |
| 155 return isolate->heap()->nan_value(); |
| 156 } else if (data[start_pos] > '9') { |
| 157 // Fast check for a junk value. A valid string may start from a |
| 158 // whitespace, a sign ('+' or '-'), the decimal point, a decimal digit |
| 159 // or the 'I' character ('Infinity'). All of that have codes not greater |
| 160 // than '9' except 'I' and . |
| 161 if (data[start_pos] != 'I' && data[start_pos] != 0xa0) { |
| 162 return isolate->heap()->nan_value(); |
| 163 } |
| 164 } else if (len - start_pos < 10 && AreDigits(data, start_pos, len)) { |
| 165 // The maximal/minimal smi has 10 digits. If the string has less digits |
| 166 // we know it will fit into the smi-data type. |
| 167 int d = ParseDecimalInteger(data, start_pos, len); |
| 168 if (minus) { |
| 169 if (d == 0) return isolate->heap()->minus_zero_value(); |
| 170 d = -d; |
| 171 } else if (!subject->HasHashCode() && len <= String::kMaxArrayIndexSize && |
| 172 (len == 1 || data[0] != '0')) { |
| 173 // String hash is not calculated yet but all the data are present. |
| 174 // Update the hash field to speed up sequential convertions. |
| 175 uint32_t hash = StringHasher::MakeArrayIndexHash(d, len); |
| 176 #ifdef DEBUG |
| 177 subject->Hash(); // Force hash calculation. |
| 178 DCHECK_EQ(static_cast<int>(subject->hash_field()), |
| 179 static_cast<int>(hash)); |
| 180 #endif |
| 181 subject->set_hash_field(hash); |
| 182 } |
| 183 return Smi::FromInt(d); |
| 184 } |
| 185 } |
| 186 |
| 187 // Slower case. |
| 188 int flags = ALLOW_HEX; |
| 189 if (FLAG_harmony_numeric_literals) { |
| 190 // The current spec draft has not updated "ToNumber Applied to the String |
| 191 // Type", https://bugs.ecmascript.org/show_bug.cgi?id=1584 |
| 192 flags |= ALLOW_OCTAL | ALLOW_BINARY; |
| 193 } |
| 194 |
| 195 return *isolate->factory()->NewNumber( |
| 196 StringToDouble(isolate->unicode_cache(), *subject, flags)); |
| 197 } |
| 198 |
| 199 |
| 200 RUNTIME_FUNCTION(Runtime_StringParseInt) { |
| 201 HandleScope handle_scope(isolate); |
| 202 DCHECK(args.length() == 2); |
| 203 CONVERT_ARG_HANDLE_CHECKED(String, subject, 0); |
| 204 CONVERT_NUMBER_CHECKED(int, radix, Int32, args[1]); |
| 205 RUNTIME_ASSERT(radix == 0 || (2 <= radix && radix <= 36)); |
| 206 |
| 207 subject = String::Flatten(subject); |
| 208 double value; |
| 209 |
| 210 { |
| 211 DisallowHeapAllocation no_gc; |
| 212 String::FlatContent flat = subject->GetFlatContent(); |
| 213 |
| 214 // ECMA-262 section 15.1.2.3, empty string is NaN |
| 215 if (flat.IsOneByte()) { |
| 216 value = |
| 217 StringToInt(isolate->unicode_cache(), flat.ToOneByteVector(), radix); |
| 218 } else { |
| 219 value = StringToInt(isolate->unicode_cache(), flat.ToUC16Vector(), radix); |
| 220 } |
| 221 } |
| 222 |
| 223 return *isolate->factory()->NewNumber(value); |
| 224 } |
| 225 |
| 226 |
| 227 RUNTIME_FUNCTION(Runtime_StringParseFloat) { |
| 228 HandleScope shs(isolate); |
| 229 DCHECK(args.length() == 1); |
| 230 CONVERT_ARG_HANDLE_CHECKED(String, subject, 0); |
| 231 |
| 232 subject = String::Flatten(subject); |
| 233 double value = StringToDouble(isolate->unicode_cache(), *subject, |
| 234 ALLOW_TRAILING_JUNK, base::OS::nan_value()); |
| 235 |
| 236 return *isolate->factory()->NewNumber(value); |
| 237 } |
| 238 |
| 239 |
| 240 RUNTIME_FUNCTION(Runtime_NumberToStringRT) { |
| 241 HandleScope scope(isolate); |
| 242 DCHECK(args.length() == 1); |
| 243 CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0); |
| 244 |
| 245 return *isolate->factory()->NumberToString(number); |
| 246 } |
| 247 |
| 248 |
| 249 RUNTIME_FUNCTION(Runtime_NumberToStringSkipCache) { |
| 250 HandleScope scope(isolate); |
| 251 DCHECK(args.length() == 1); |
| 252 CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0); |
| 253 |
| 254 return *isolate->factory()->NumberToString(number, false); |
| 255 } |
| 256 |
| 257 |
| 258 RUNTIME_FUNCTION(Runtime_NumberToInteger) { |
| 259 HandleScope scope(isolate); |
| 260 DCHECK(args.length() == 1); |
| 261 |
| 262 CONVERT_DOUBLE_ARG_CHECKED(number, 0); |
| 263 return *isolate->factory()->NewNumber(DoubleToInteger(number)); |
| 264 } |
| 265 |
| 266 |
| 267 RUNTIME_FUNCTION(Runtime_NumberToIntegerMapMinusZero) { |
| 268 HandleScope scope(isolate); |
| 269 DCHECK(args.length() == 1); |
| 270 |
| 271 CONVERT_DOUBLE_ARG_CHECKED(number, 0); |
| 272 double double_value = DoubleToInteger(number); |
| 273 // Map both -0 and +0 to +0. |
| 274 if (double_value == 0) double_value = 0; |
| 275 |
| 276 return *isolate->factory()->NewNumber(double_value); |
| 277 } |
| 278 |
| 279 |
| 280 RUNTIME_FUNCTION(Runtime_NumberToJSUint32) { |
| 281 HandleScope scope(isolate); |
| 282 DCHECK(args.length() == 1); |
| 283 |
| 284 CONVERT_NUMBER_CHECKED(int32_t, number, Uint32, args[0]); |
| 285 return *isolate->factory()->NewNumberFromUint(number); |
| 286 } |
| 287 |
| 288 |
| 289 RUNTIME_FUNCTION(Runtime_NumberToJSInt32) { |
| 290 HandleScope scope(isolate); |
| 291 DCHECK(args.length() == 1); |
| 292 |
| 293 CONVERT_DOUBLE_ARG_CHECKED(number, 0); |
| 294 return *isolate->factory()->NewNumberFromInt(DoubleToInt32(number)); |
| 295 } |
| 296 |
| 297 |
| 298 // Converts a Number to a Smi, if possible. Returns NaN if the number is not |
| 299 // a small integer. |
| 300 RUNTIME_FUNCTION(Runtime_NumberToSmi) { |
| 301 SealHandleScope shs(isolate); |
| 302 DCHECK(args.length() == 1); |
| 303 CONVERT_ARG_CHECKED(Object, obj, 0); |
| 304 if (obj->IsSmi()) { |
| 305 return obj; |
| 306 } |
| 307 if (obj->IsHeapNumber()) { |
| 308 double value = HeapNumber::cast(obj)->value(); |
| 309 int int_value = FastD2I(value); |
| 310 if (value == FastI2D(int_value) && Smi::IsValid(int_value)) { |
| 311 return Smi::FromInt(int_value); |
| 312 } |
| 313 } |
| 314 return isolate->heap()->nan_value(); |
| 315 } |
| 316 |
| 317 |
| 318 RUNTIME_FUNCTION(Runtime_NumberAdd) { |
| 319 HandleScope scope(isolate); |
| 320 DCHECK(args.length() == 2); |
| 321 |
| 322 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 323 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 324 return *isolate->factory()->NewNumber(x + y); |
| 325 } |
| 326 |
| 327 |
| 328 RUNTIME_FUNCTION(Runtime_NumberSub) { |
| 329 HandleScope scope(isolate); |
| 330 DCHECK(args.length() == 2); |
| 331 |
| 332 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 333 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 334 return *isolate->factory()->NewNumber(x - y); |
| 335 } |
| 336 |
| 337 |
| 338 RUNTIME_FUNCTION(Runtime_NumberMul) { |
| 339 HandleScope scope(isolate); |
| 340 DCHECK(args.length() == 2); |
| 341 |
| 342 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 343 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 344 return *isolate->factory()->NewNumber(x * y); |
| 345 } |
| 346 |
| 347 |
| 348 RUNTIME_FUNCTION(Runtime_NumberUnaryMinus) { |
| 349 HandleScope scope(isolate); |
| 350 DCHECK(args.length() == 1); |
| 351 |
| 352 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 353 return *isolate->factory()->NewNumber(-x); |
| 354 } |
| 355 |
| 356 |
| 357 RUNTIME_FUNCTION(Runtime_NumberDiv) { |
| 358 HandleScope scope(isolate); |
| 359 DCHECK(args.length() == 2); |
| 360 |
| 361 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 362 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 363 return *isolate->factory()->NewNumber(x / y); |
| 364 } |
| 365 |
| 366 |
| 367 RUNTIME_FUNCTION(Runtime_NumberMod) { |
| 368 HandleScope scope(isolate); |
| 369 DCHECK(args.length() == 2); |
| 370 |
| 371 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 372 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 373 return *isolate->factory()->NewNumber(modulo(x, y)); |
| 374 } |
| 375 |
| 376 |
| 377 RUNTIME_FUNCTION(Runtime_NumberImul) { |
| 378 HandleScope scope(isolate); |
| 379 DCHECK(args.length() == 2); |
| 380 |
| 381 // We rely on implementation-defined behavior below, but at least not on |
| 382 // undefined behavior. |
| 383 CONVERT_NUMBER_CHECKED(uint32_t, x, Int32, args[0]); |
| 384 CONVERT_NUMBER_CHECKED(uint32_t, y, Int32, args[1]); |
| 385 int32_t product = static_cast<int32_t>(x * y); |
| 386 return *isolate->factory()->NewNumberFromInt(product); |
| 387 } |
| 388 |
| 389 |
| 390 RUNTIME_FUNCTION(Runtime_NumberOr) { |
| 391 HandleScope scope(isolate); |
| 392 DCHECK(args.length() == 2); |
| 393 |
| 394 CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]); |
| 395 CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]); |
| 396 return *isolate->factory()->NewNumberFromInt(x | y); |
| 397 } |
| 398 |
| 399 |
| 400 RUNTIME_FUNCTION(Runtime_NumberAnd) { |
| 401 HandleScope scope(isolate); |
| 402 DCHECK(args.length() == 2); |
| 403 |
| 404 CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]); |
| 405 CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]); |
| 406 return *isolate->factory()->NewNumberFromInt(x & y); |
| 407 } |
| 408 |
| 409 |
| 410 RUNTIME_FUNCTION(Runtime_NumberXor) { |
| 411 HandleScope scope(isolate); |
| 412 DCHECK(args.length() == 2); |
| 413 |
| 414 CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]); |
| 415 CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]); |
| 416 return *isolate->factory()->NewNumberFromInt(x ^ y); |
| 417 } |
| 418 |
| 419 |
| 420 RUNTIME_FUNCTION(Runtime_NumberShl) { |
| 421 HandleScope scope(isolate); |
| 422 DCHECK(args.length() == 2); |
| 423 |
| 424 CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]); |
| 425 CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]); |
| 426 return *isolate->factory()->NewNumberFromInt(x << (y & 0x1f)); |
| 427 } |
| 428 |
| 429 |
| 430 RUNTIME_FUNCTION(Runtime_NumberShr) { |
| 431 HandleScope scope(isolate); |
| 432 DCHECK(args.length() == 2); |
| 433 |
| 434 CONVERT_NUMBER_CHECKED(uint32_t, x, Uint32, args[0]); |
| 435 CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]); |
| 436 return *isolate->factory()->NewNumberFromUint(x >> (y & 0x1f)); |
| 437 } |
| 438 |
| 439 |
| 440 RUNTIME_FUNCTION(Runtime_NumberSar) { |
| 441 HandleScope scope(isolate); |
| 442 DCHECK(args.length() == 2); |
| 443 |
| 444 CONVERT_NUMBER_CHECKED(int32_t, x, Int32, args[0]); |
| 445 CONVERT_NUMBER_CHECKED(int32_t, y, Int32, args[1]); |
| 446 return *isolate->factory()->NewNumberFromInt( |
| 447 ArithmeticShiftRight(x, y & 0x1f)); |
| 448 } |
| 449 |
| 450 |
| 451 RUNTIME_FUNCTION(Runtime_NumberEquals) { |
| 452 SealHandleScope shs(isolate); |
| 453 DCHECK(args.length() == 2); |
| 454 |
| 455 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 456 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 457 if (std::isnan(x)) return Smi::FromInt(NOT_EQUAL); |
| 458 if (std::isnan(y)) return Smi::FromInt(NOT_EQUAL); |
| 459 if (x == y) return Smi::FromInt(EQUAL); |
| 460 Object* result; |
| 461 if ((fpclassify(x) == FP_ZERO) && (fpclassify(y) == FP_ZERO)) { |
| 462 result = Smi::FromInt(EQUAL); |
| 463 } else { |
| 464 result = Smi::FromInt(NOT_EQUAL); |
| 465 } |
| 466 return result; |
| 467 } |
| 468 |
| 469 |
| 470 RUNTIME_FUNCTION(Runtime_NumberCompare) { |
| 471 SealHandleScope shs(isolate); |
| 472 DCHECK(args.length() == 3); |
| 473 |
| 474 CONVERT_DOUBLE_ARG_CHECKED(x, 0); |
| 475 CONVERT_DOUBLE_ARG_CHECKED(y, 1); |
| 476 CONVERT_ARG_HANDLE_CHECKED(Object, uncomparable_result, 2) |
| 477 if (std::isnan(x) || std::isnan(y)) return *uncomparable_result; |
| 478 if (x == y) return Smi::FromInt(EQUAL); |
| 479 if (isless(x, y)) return Smi::FromInt(LESS); |
| 480 return Smi::FromInt(GREATER); |
| 481 } |
| 482 |
| 483 |
| 484 // Compare two Smis as if they were converted to strings and then |
| 485 // compared lexicographically. |
| 486 RUNTIME_FUNCTION(Runtime_SmiLexicographicCompare) { |
| 487 SealHandleScope shs(isolate); |
| 488 DCHECK(args.length() == 2); |
| 489 CONVERT_SMI_ARG_CHECKED(x_value, 0); |
| 490 CONVERT_SMI_ARG_CHECKED(y_value, 1); |
| 491 |
| 492 // If the integers are equal so are the string representations. |
| 493 if (x_value == y_value) return Smi::FromInt(EQUAL); |
| 494 |
| 495 // If one of the integers is zero the normal integer order is the |
| 496 // same as the lexicographic order of the string representations. |
| 497 if (x_value == 0 || y_value == 0) |
| 498 return Smi::FromInt(x_value < y_value ? LESS : GREATER); |
| 499 |
| 500 // If only one of the integers is negative the negative number is |
| 501 // smallest because the char code of '-' is less than the char code |
| 502 // of any digit. Otherwise, we make both values positive. |
| 503 |
| 504 // Use unsigned values otherwise the logic is incorrect for -MIN_INT on |
| 505 // architectures using 32-bit Smis. |
| 506 uint32_t x_scaled = x_value; |
| 507 uint32_t y_scaled = y_value; |
| 508 if (x_value < 0 || y_value < 0) { |
| 509 if (y_value >= 0) return Smi::FromInt(LESS); |
| 510 if (x_value >= 0) return Smi::FromInt(GREATER); |
| 511 x_scaled = -x_value; |
| 512 y_scaled = -y_value; |
| 513 } |
| 514 |
| 515 static const uint32_t kPowersOf10[] = { |
| 516 1, 10, 100, 1000, |
| 517 10 * 1000, 100 * 1000, 1000 * 1000, 10 * 1000 * 1000, |
| 518 100 * 1000 * 1000, 1000 * 1000 * 1000}; |
| 519 |
| 520 // If the integers have the same number of decimal digits they can be |
| 521 // compared directly as the numeric order is the same as the |
| 522 // lexicographic order. If one integer has fewer digits, it is scaled |
| 523 // by some power of 10 to have the same number of digits as the longer |
| 524 // integer. If the scaled integers are equal it means the shorter |
| 525 // integer comes first in the lexicographic order. |
| 526 |
| 527 // From http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10 |
| 528 int x_log2 = IntegerLog2(x_scaled); |
| 529 int x_log10 = ((x_log2 + 1) * 1233) >> 12; |
| 530 x_log10 -= x_scaled < kPowersOf10[x_log10]; |
| 531 |
| 532 int y_log2 = IntegerLog2(y_scaled); |
| 533 int y_log10 = ((y_log2 + 1) * 1233) >> 12; |
| 534 y_log10 -= y_scaled < kPowersOf10[y_log10]; |
| 535 |
| 536 int tie = EQUAL; |
| 537 |
| 538 if (x_log10 < y_log10) { |
| 539 // X has fewer digits. We would like to simply scale up X but that |
| 540 // might overflow, e.g when comparing 9 with 1_000_000_000, 9 would |
| 541 // be scaled up to 9_000_000_000. So we scale up by the next |
| 542 // smallest power and scale down Y to drop one digit. It is OK to |
| 543 // drop one digit from the longer integer since the final digit is |
| 544 // past the length of the shorter integer. |
| 545 x_scaled *= kPowersOf10[y_log10 - x_log10 - 1]; |
| 546 y_scaled /= 10; |
| 547 tie = LESS; |
| 548 } else if (y_log10 < x_log10) { |
| 549 y_scaled *= kPowersOf10[x_log10 - y_log10 - 1]; |
| 550 x_scaled /= 10; |
| 551 tie = GREATER; |
| 552 } |
| 553 |
| 554 if (x_scaled < y_scaled) return Smi::FromInt(LESS); |
| 555 if (x_scaled > y_scaled) return Smi::FromInt(GREATER); |
| 556 return Smi::FromInt(tie); |
| 557 } |
| 558 |
| 559 |
| 560 RUNTIME_FUNCTION(RuntimeReference_NumberToString) { |
| 561 SealHandleScope shs(isolate); |
| 562 return __RT_impl_Runtime_NumberToStringRT(args, isolate); |
| 563 } |
| 564 } |
| 565 } // namespace v8::internal |
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