Fixing bug introduced in r10210 that crashes v8 raytrace benchmark.

src/arm/code-stubs-arm.cc

 // Copyright 2011 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 3497 matching lines @@
     __ JumpIfNotSmi(exponent, &exponent_not_smi);
     __ SmiUntag(exponent);
     __ jmp(&int_exponent);
 
     __ bind(&exponent_not_smi);
     __ vldr(double_exponent,
             FieldMemOperand(exponent, HeapNumber::kValueOffset));
   }
 
   if (exponent_type_ != INTEGER) {
+    Label int_exponent_convert;
     // Detect integer exponents stored as double.
     __ vcvt_u32_f64(single_scratch, double_exponent);
     // We do not check for NaN or Infinity here because comparing numbers on
     // ARM correctly distinguishes NaNs.  We end up calling the built-in.
     __ vcvt_f64_u32(double_scratch, single_scratch);
     __ VFPCompareAndSetFlags(double_scratch, double_exponent);
-    __ vmov(exponent, single_scratch, eq);

[Yang, 2011/12/09 12:04:37]

We try to detect integer values saved in the double register double_exponent by
converting it to integer and back to double, then comparing. Unlike on intel
architectures, single_scratch saving the intermediate integer is clobbered
during the second conversion.

-    __ b(eq, &int_exponent);
+    __ b(eq, &int_exponent_convert);
 
     if (exponent_type_ == ON_STACK) {
       // Detect square root case.  Crankshaft detects constant +/-0.5 at
       // compile time and uses DoMathPowHalf instead.  We then skip this check
       // for non-constant cases of +/-0.5 as these hardly occur.
       Label not_plus_half;
 
       // Test for 0.5.
       __ vmov(double_scratch, 0.5);
       __ VFPCompareAndSetFlags(double_exponent, double_scratch);
@@ skipping 36 matching lines @@
       AllowExternalCallThatCantCauseGC scope(masm);
       __ PrepareCallCFunction(0, 2, scratch);
       __ SetCallCDoubleArguments(double_base, double_exponent);
       __ CallCFunction(
           ExternalReference::power_double_double_function(masm->isolate()),
           0, 2);
     }
     __ pop(lr);
     __ GetCFunctionDoubleResult(double_result);
     __ jmp(&done);
+
+    __ bind(&int_exponent_convert);
+    __ vcvt_u32_f64(single_scratch, double_exponent);
+    __ vmov(exponent, single_scratch);
   }
 
   // Calculate power with integer exponent.
   __ bind(&int_exponent);
 
   __ mov(scratch, exponent);  // Back up exponent.
   __ vmov(double_scratch, double_base);  // Back up base.
   __ vmov(double_result, 1.0);
 
   // Get absolute value of exponent.
@@ skipping 30 matching lines @@
 
     // The stub is called from non-optimized code, which expects the result
     // as heap number in exponent.
     __ bind(&done);
     __ AllocateHeapNumber(
         heapnumber, scratch, scratch2, heapnumbermap, &call_runtime);
     __ vstr(double_result,
             FieldMemOperand(heapnumber, HeapNumber::kValueOffset));
     ASSERT(heapnumber.is(r0));
     __ IncrementCounter(counters->math_pow(), 1, scratch, scratch2);
-    __ Ret(2 * kPointerSize);
+    __ Ret(2);

[Yang, 2011/12/09 12:04:37]

On ARM we don't multiply with kPointerSize.

   } else {
     __ push(lr);
     {
       AllowExternalCallThatCantCauseGC scope(masm);
       __ PrepareCallCFunction(0, 2, scratch);
       __ SetCallCDoubleArguments(double_base, double_exponent);
       __ CallCFunction(
           ExternalReference::power_double_double_function(masm->isolate()),
           0, 2);
     }
@@ skipping 3714 matching lines @@
   __ StoreNumberToDoubleElements(r0, r3, r1, r5, r6, r7, r9, r10,
                                  &slow_elements);
   __ Ret();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM