ARM: Enable VFP default NaN mode

src/arm/macro-assembler-arm.h

Index: src/arm/macro-assembler-arm.h
diff --git a/src/arm/macro-assembler-arm.h b/src/arm/macro-assembler-arm.h
index 75ff64fc055570e8031254376c656d74cfd28f62..97551e896c6a8fe85717f0f7f45b47120925f23d 100644
--- a/src/arm/macro-assembler-arm.h
+++ b/src/arm/macro-assembler-arm.h
@@ -460,6 +460,15 @@ class MacroAssembler: public Assembler {
             const MemOperand& dst,
             Condition cond = al);
 
+  // Ensure that FPSCR contains values needed by JavaScript.
+  // We need the NaNModeControlBit to be sure that operations like
+  // vadd and vsub generate the Canonical NaN (if a NaN must be generated).
+  // In VFP3 it will be always the Canonical NaN.
+  // In VFP2 it will be either the Canonical NaN or the negative version
+  // of the Canonical NaN. It doesn't matter if we have two values. The aim
+  // is to be sure to never generate the hole NaN.
+  void VFPEnsureFPSCRState(Register scratch);
+
   // Compare double values and move the result to the normal condition flags.
   void VFPCompareAndSetFlags(const DwVfpRegister src1,
                              const DwVfpRegister src2,