ARM: Make use of d16-d31 when available.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 38015b4fe442dbaac45f0590ba3db1e4ef0df0dc..2e918804920247e01517224d74a097115c7904b6 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3179,8 +3179,8 @@ void LCodeGen::DoLoadKeyedExternalArray(LLoadKeyed* instr) {
     if (CpuFeatures::IsSupported(VFP2)) {
       CpuFeatures::Scope scope(VFP2);
       if (elements_kind == EXTERNAL_FLOAT_ELEMENTS) {
-        __ vldr(result.low(), scratch0(), additional_offset);
-        __ vcvt_f64_f32(result, result.low());
+        __ vldr(kScratchDoubleReg.low(), scratch0(), additional_offset);
+        __ vcvt_f64_f32(result, kScratchDoubleReg.low());
       } else  {  // i.e. elements_kind == EXTERNAL_DOUBLE_ELEMENTS
         __ vldr(result, scratch0(), additional_offset);
       }