ARM: Make use of d16-d31 when available.

src/arm/code-stubs-arm.h

Index: src/arm/code-stubs-arm.h
diff --git a/src/arm/code-stubs-arm.h b/src/arm/code-stubs-arm.h
index 0443cf799cc08e5d83e8ebe88f6de929dc8b5d12..a5aebee946fac1525f39dae88de7c88c53173f06 100644
--- a/src/arm/code-stubs-arm.h
+++ b/src/arm/code-stubs-arm.h
@@ -472,9 +472,11 @@ class RecordWriteStub: public CodeStub {
         CpuFeatures::Scope scope(VFP2);
         masm->sub(sp,
                   sp,
-                  Operand(kDoubleSize * (DwVfpRegister::kNumRegisters - 1)));
+                  Operand(kDoubleSize *
+                          (DwVfpRegister::NumAvailableRegisters() - 1)));
         // Save all VFP registers except d0.
-        for (int i = DwVfpRegister::kNumRegisters - 1; i > 0; i--) {
+        // TODO(hans): We should probably save d0 too. And maybe use vstm.
+        for (int i = DwVfpRegister::NumAvailableRegisters() - 1; i > 0; i--) {
           DwVfpRegister reg = DwVfpRegister::from_code(i);
           masm->vstr(reg, MemOperand(sp, (i - 1) * kDoubleSize));
         }
@@ -486,13 +488,15 @@ class RecordWriteStub: public CodeStub {
       if (mode == kSaveFPRegs) {
         CpuFeatures::Scope scope(VFP2);
         // Restore all VFP registers except d0.
-        for (int i = DwVfpRegister::kNumRegisters - 1; i > 0; i--) {
+        // TODO(hans): We should probably restore d0 too. And maybe use vldm.
+        for (int i = DwVfpRegister::NumAvailableRegisters() - 1; i > 0; i--) {
           DwVfpRegister reg = DwVfpRegister::from_code(i);
           masm->vldr(reg, MemOperand(sp, (i - 1) * kDoubleSize));
         }
         masm->add(sp,
                   sp,
-                  Operand(kDoubleSize * (DwVfpRegister::kNumRegisters - 1)));
+                  Operand(kDoubleSize *
+                          (DwVfpRegister::NumAvailableRegisters() - 1)));
       }
       masm->ldm(ia_w, sp, (kCallerSaved | lr.bit()) & ~scratch1_.bit());
     }