[turbofan] Prevent storing signalling NaNs into holey double arrays.

src/compiler/mips/code-generator-mips.cc

 // Copyright 2014 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 "src/ast/scopes.h"
 #include "src/compiler/code-generator.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/osr.h"
@@ skipping 1240 matching lines @@
       break;
     case kMipsFloat64ExtractHighWord32:
       __ FmoveHigh(i.OutputRegister(), i.InputDoubleRegister(0));
       break;
     case kMipsFloat64InsertLowWord32:
       __ FmoveLow(i.OutputDoubleRegister(), i.InputRegister(1));
       break;
     case kMipsFloat64InsertHighWord32:
       __ FmoveHigh(i.OutputDoubleRegister(), i.InputRegister(1));
       break;
+    case kMipsFloat64SilenceNaN: {
+      FPURegister value = i.InputDoubleRegister(0);
+      FPURegister result = i.OutputDoubleRegister();
+      Register scratch0 = i.TempRegister(0);
+      Label is_nan, not_nan;
+      __ BranchF(NULL, &is_nan, eq, value, value);
+      __ Branch(&not_nan);
+      __ bind(&is_nan);
+      __ LoadRoot(scratch0, Heap::kNanValueRootIndex);
+      __ ldc1(result, FieldMemOperand(scratch0, HeapNumber::kValueOffset));
+      __ bind(&not_nan);
+      break;
+    }
+
     // ... more basic instructions ...
 
     case kMipsLbu:
       __ lbu(i.OutputRegister(), i.MemoryOperand());
       break;
     case kMipsLb:
       __ lb(i.OutputRegister(), i.MemoryOperand());
       break;
     case kMipsSb:
       __ sb(i.InputRegister(2), i.MemoryOperand());
@@ skipping 743 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8