Allow the optimizing code generator to call Math.pow with untagged doubles.

src/assembler.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 48 matching lines @@
 #error "Unknown architecture."
 #endif  // Target architecture.
 #endif  // V8_INTERPRETED_REGEXP
 
 namespace v8 {
 namespace internal {
 
 
 const double DoubleConstant::min_int = kMinInt;
 const double DoubleConstant::one_half = 0.5;
+const double DoubleConstant::negative_infinity = -V8_INFINITY;
 
 
 // -----------------------------------------------------------------------------
 // Implementation of Label
 
 int Label::pos() const {
   if (pos_ < 0) return -pos_ - 1;
   if (pos_ > 0) return  pos_ - 1;
   UNREACHABLE();
   return 0;
@@ skipping 636 matching lines @@
       const_cast<double*>(&DoubleConstant::min_int)));
 }
 
 
 ExternalReference ExternalReference::address_of_one_half() {
   return ExternalReference(reinterpret_cast<void*>(
       const_cast<double*>(&DoubleConstant::one_half)));
 }
 
 
+ExternalReference ExternalReference::address_of_negative_infinity() {
+  return ExternalReference(reinterpret_cast<void*>(
+      const_cast<double*>(&DoubleConstant::negative_infinity)));
+}
+
+
 #ifndef V8_INTERPRETED_REGEXP
 
 ExternalReference ExternalReference::re_check_stack_guard_state() {
   Address function;
 #ifdef V8_TARGET_ARCH_X64
   function = FUNCTION_ADDR(RegExpMacroAssemblerX64::CheckStackGuardState);
 #elif V8_TARGET_ARCH_IA32
   function = FUNCTION_ADDR(RegExpMacroAssemblerIA32::CheckStackGuardState);
 #elif V8_TARGET_ARCH_ARM
   function = FUNCTION_ADDR(RegExpMacroAssemblerARM::CheckStackGuardState);
@@ skipping 51 matching lines @@
 static double div_two_doubles(double x, double y) {
   return x / y;
 }
 
 
 static double mod_two_doubles(double x, double y) {
   return modulo(x, y);
 }
 
 
+// Helper function to compute x^y, where y is known to be an
+// integer. Uses binary decomposition to limit the number of
+// multiplications; see the discussion in "Hacker's Delight" by Henry
+// S. Warren, Jr., figure 11-6, page 213.
+double power_double_int(double x, int y) {
+  double m = (y < 0) ? 1/x : x;

[Florian Schneider, 2010/12/08 14:09:27]

--> 1 / x

[William Hesse, 2010/12/08 14:53:16]

Done.

+  unsigned n = (y < 0) ? -y : y;
+  double p = 1;
+  while (n != 0) {
+    if ((n & 1) != 0) p *= m;
+    m *= m;
+    if ((n & 2) != 0) p *= m;
+    m *= m;
+    n >>= 2;
+  }
+  return p;
+}
+
+
+double power_double_double(double x, double y) {
+  int y_int = static_cast<int>(y);
+  if (y == y_int) {
+    return power_double_int(x, y_int);  // Returns 1.0 for exponent 0.
+  }
+  if (!isinf(x)) {
+    if (y == 0.5) return sqrt(x);
+    if (y == -0.5) return 1.0 / sqrt(x);
+  }
+  if (isnan(y) || ((x == 1 || x == -1) && isinf(y))) {
+    return OS::nan_value();
+  }
+  return pow(x, y);
+}
+
+
+ExternalReference ExternalReference::power_double_double_function() {
+  return ExternalReference(Redirect(FUNCTION_ADDR(power_double_double)));
+}
+
+
+ExternalReference ExternalReference::power_double_int_function() {
+  return ExternalReference(Redirect(FUNCTION_ADDR(power_double_int)));
+}
+
+
 static int native_compare_doubles(double y, double x) {
   if (x == y) return EQUAL;
   return x < y ? LESS : GREATER;
 }
 
 
 ExternalReference ExternalReference::double_fp_operation(
     Token::Value operation) {
   typedef double BinaryFPOperation(double x, double y);
   BinaryFPOperation* function = NULL;
@@ skipping 77 matching lines @@
     assembler_->RecordRelocInfo(RelocInfo::POSITION, state_.current_position);
     state_.written_position = state_.current_position;
     written = true;
   }
 
   // Return whether something was written.
   return written;
 }
 
 } }  // namespace v8::internal