[Isolates] Merge 7051:7083 from bleeding_edge to isolates.

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 855 matching lines @@
   // src1: higher (exponent) part of the double value.
   // src2: lower (mantissa) part of the double value.
   // scratch: unbiased exponent.
 
   // Fast cases. Check for obvious non 32-bit integer values.
   // Negative exponent cannot yield 32-bit integers.
   __ b(mi, not_int32);
   // Exponent greater than 31 cannot yield 32-bit integers.
   // Also, a positive value with an exponent equal to 31 is outside of the
   // signed 32-bit integer range.
-  __ tst(src1, Operand(HeapNumber::kSignMask));
-  __ cmp(scratch, Operand(30), eq);  // Executed for positive. If exponent is 30
-                                     // the gt condition will be "correct" and
-                                     // the next instruction will be skipped.
-  __ cmp(scratch, Operand(31), ne);  // Executed for negative and positive where
-                                     // exponent is not 30.
+  // Another way to put it is that if (exponent - signbit) > 30 then the
+  // number cannot be represented as an int32.
+  Register tmp = dst;
+  __ sub(tmp, scratch, Operand(src1, LSR, 31));
+  __ cmp(tmp, Operand(30));
   __ b(gt, not_int32);
   // - Bits [21:0] in the mantissa are not null.
   __ tst(src2, Operand(0x3fffff));
   __ b(ne, not_int32);
 
   // Otherwise the exponent needs to be big enough to shift left all the
   // non zero bits left. So we need the (30 - exponent) last bits of the
   // 31 higher bits of the mantissa to be null.
   // Because bits [21:0] are null, we can check instead that the
   // (32 - exponent) last bits of the 32 higher bits of the mantisssa are null.
@@ skipping 6002 matching lines @@
   __ strb(untagged_value, MemOperand(external_pointer, untagged_key));
   __ Ret();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM