Optimize isFinite and isNaN.

Arithmetic on infinities and NaN is much slower than doing several exact comparisons.

Review URL: http://codereview.chromium.org/7830036

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9134 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/macros.py

@@ -122,7 +122,7 @@ macro IS_SPEC_OBJECT(arg) = (%_IsSpecObject(arg));
 
 # Inline macros. Use %IS_VAR to make sure arg is evaluated only once.
 macro NUMBER_IS_NAN(arg) = (!%_IsSmi(%IS_VAR(arg)) && !(arg == arg));
-macro NUMBER_IS_FINITE(arg) = (%_IsSmi(%IS_VAR(arg)) || arg - arg == 0);
+macro NUMBER_IS_FINITE(arg) = (%_IsSmi(%IS_VAR(arg)) || ((arg == arg) && (arg != 1/0) && (arg != -1/0)));
 macro TO_INTEGER(arg) = (%_IsSmi(%IS_VAR(arg)) ? arg : %NumberToInteger(ToNumber(arg)));
 macro TO_INTEGER_MAP_MINUS_ZERO(arg) = (%_IsSmi(%IS_VAR(arg)) ? arg : %NumberToIntegerMapMinusZero(ToNumber(arg)));
 macro TO_INT32(arg) = (%_IsSmi(%IS_VAR(arg)) ? arg : (arg >> 0));

src/v8natives.js

@@ -41,7 +41,6 @@
 const $isNaN = GlobalIsNaN;
 const $isFinite = GlobalIsFinite;
 
-
 // ----------------------------------------------------------------------------
 
 
@@ -122,17 +121,15 @@ function SetUpLockedPrototype(constructor, fields, methods) {
 
 // ECMA 262 - 15.1.4
 function GlobalIsNaN(number) {
-  var n = ToNumber(number);
-  return NUMBER_IS_NAN(n);
+  if (!IS_NUMBER(number)) number = NonNumberToNumber(number);
+  return NUMBER_IS_NAN(number);
 }
 
 
 // ECMA 262 - 15.1.5
 function GlobalIsFinite(number) {
   if (!IS_NUMBER(number)) number = NonNumberToNumber(number);
-
-  // NaN - NaN == NaN, Infinity - Infinity == NaN, -Infinity - -Infinity == NaN.
-  return %_IsSmi(number) || number - number == 0;
+  return NUMBER_IS_FINITE(number);
 }