MIPS64: Improve and fix nan hole checks and canonicalization.

src/mips64/macro-assembler-mips64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits.h>  // For LONG_MIN, LONG_MAX.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS64
 
@@ skipping 3866 matching lines @@
            scratch1,
            Heap::kHeapNumberMapRootIndex,
            fail,
            DONT_DO_SMI_CHECK);
 
   // Double value, turn potential sNaN into qNan.
   DoubleRegister double_result = f0;
   DoubleRegister double_scratch = f2;
 
   ldc1(double_result, FieldMemOperand(value_reg, HeapNumber::kValueOffset));
+  Branch(USE_DELAY_SLOT, &done);  // Canonicalization is one instruction.
   FPUCanonicalizeNaN(double_result, double_result);
-  Branch(&done);
 
   bind(&smi_value);
   // scratch1 is now effective address of the double element.

[paul.l..., 2015/02/25 16:21:38]

nit: It looks like this comment is now stale - scratch1 is only used in
CheckMap() above, and should have map pointer. Can you correct this as
necessary.

   // Untag and transfer.
-  mthc1(value_reg, double_scratch);
+  dsrl32(at, value_reg, 0);
+  mtc1(at, double_scratch);
   cvt_d_w(double_result, double_scratch);
 
   bind(&done);
   Daddu(scratch1, elements_reg,
       Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag -
               elements_offset));
   dsra(scratch2, key_reg, 32 - kDoubleSizeLog2);
   Daddu(scratch1, scratch1, scratch2);
   sdc1(double_result, MemOperand(scratch1, 0));
 }
@@ skipping 2287 matching lines @@
   }
   if (mag.shift > 0) sra(result, result, mag.shift);
   srl(at, dividend, 31);
   Addu(result, result, Operand(at));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS64