Strtod fast-case that uses DiyFps and cached powers of ten.

src/cached-powers.h

Index: src/cached-powers.h
diff --git a/src/cached-powers.h b/src/cached-powers.h
index 0c7834317032aeee37ea71f301f119aca3a788e7..2ae56196a32a896dfaf5a9f1713c2937a8eb6d36 100644
--- a/src/cached-powers.h
+++ b/src/cached-powers.h
@@ -33,10 +33,32 @@
 namespace v8 {
 namespace internal {
 
-void GetCachedPowerForBinaryExponentRange(int min_exponent,
-                                          int max_exponent,
-                                          DiyFp* power,
-                                          int* decimal_exponent);
+class PowersOfTenCache {
+ public:
+
+  // Not all powers of ten are cached. The decimal exponent of two neighboring
+  // cached numbers will differ by kDecimalExponentDistance.
+  static const int kDecimalExponentDistance;
+
+  static const int kMinDecimalExponent;
+  static const int kMaxDecimalExponent;
+
+  // Returns a cached power-of-ten with a binary exponent in the range
+  // [min_exponent; max_exponent] (boundaries included).
+  static void GetCachedPowerForBinaryExponentRange(int min_exponent,
+                                                   int max_exponent,
+                                                   DiyFp* power,
+                                                   int* decimal_exponent);
+
+  // Returns a cached power of ten x ~= 10^k such that
+  //   k <= decimal_exponent < k + kCachedPowersDecimalDistance.
+  // The given decimal_exponent must satisfy
+  //   kMinDecimalExponent <= requested_exponent, and
+  //   requested_exponent < kMaxDecimalExponent + kDecimalExponentDistance.
+  static void GetCachedPowerForDecimalExponent(int requested_exponent,
+                                               DiyFp* power,
+                                               int* found_exponent);
+};
 
 } }  // namespace v8::internal