Ensure consistency of Math.sqrt on Intel platforms.

src/runtime.cc

 // Copyright 2012 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
@@ skipping 7423 matching lines @@
     int y = args.smi_at(1);
     return isolate->heap()->NumberFromDouble(power_double_int(x, y));
   }
 
   CONVERT_DOUBLE_ARG_CHECKED(y, 1);
   int y_int = static_cast<int>(y);
   double result;
   if (y == y_int) {
     result = power_double_int(x, y_int);  // Returns 1 if exponent is 0.
   } else  if (y == 0.5) {
-    result = (isinf(x)) ? V8_INFINITY : sqrt(x + 0.0);  // Convert -0 to +0.
+    // Convert -0 to +0.

[Sven Panne, 2012/03/12 13:23:46]

This comment refers to the last part of the ternary ? operator, not the whole
statement.

+    result = (isinf(x)) ? V8_INFINITY : fast_sqrt(x + 0.0);
   } else if (y == -0.5) {
-    result = (isinf(x)) ? 0 : 1.0 / sqrt(x + 0.0);  // Convert -0 to +0.
+    // Convert -0 to +0.

[Sven Panne, 2012/03/12 13:23:46]

See above.

+    result = (isinf(x)) ? 0 : 1.0 / fast_sqrt(x + 0.0);
   } else {
     result = power_double_double(x, y);
   }
   if (isnan(result)) return isolate->heap()->nan_value();
   return isolate->heap()->AllocateHeapNumber(result);
 }
 
 // Fast version of Math.pow if we know that y is not an integer and y is not
 // -0.5 or 0.5.  Used as slow case from full codegen.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_pow_cfunction) {
@@ skipping 65 matching lines @@
   return isolate->transcendental_cache()->Get(TranscendentalCache::SIN, x);
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_sqrt) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
   isolate->counters()->math_sqrt()->Increment();
 
   CONVERT_DOUBLE_ARG_CHECKED(x, 0);
-  return isolate->heap()->AllocateHeapNumber(sqrt(x));
+  return isolate->heap()->AllocateHeapNumber(fast_sqrt(x));
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_tan) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
   isolate->counters()->math_tan()->Increment();
 
   CONVERT_DOUBLE_ARG_CHECKED(x, 0);
   return isolate->transcendental_cache()->Get(TranscendentalCache::TAN, x);
@@ skipping 5778 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal