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

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

Index: src/compiler/mips/code-generator-mips.cc
diff --git a/src/compiler/mips/code-generator-mips.cc b/src/compiler/mips/code-generator-mips.cc
index 9401e20556bc927d858705f3b77fb9beab80096e..1ed85ac06935b50eb658fe24905db5591e04f8dc 100644
--- a/src/compiler/mips/code-generator-mips.cc
+++ b/src/compiler/mips/code-generator-mips.cc
@@ -1258,6 +1258,20 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     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: