ARM: use vstm/vldm when possible.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index bcc985ac5a074e9ae14892d159e5c7cd1afd52b4..90601952299e31a4210e2b9dccbbb489991a45c8 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -620,22 +620,26 @@ void MacroAssembler::PushSafepointRegistersAndDoubles() {
   // Number of d-regs not known at snapshot time.
   ASSERT(!Serializer::enabled());
   PushSafepointRegisters();
-  sub(sp, sp, Operand(DwVfpRegister::NumAllocatableRegisters() *
-                      kDoubleSize));
-  for (int i = 0; i < DwVfpRegister::NumAllocatableRegisters(); i++) {
-    vstr(DwVfpRegister::FromAllocationIndex(i), sp, i * kDoubleSize);
+  // Only save allocatable registers.
+  ASSERT(kScratchDoubleReg.is(d15) && kDoubleRegZero.is(d14));
+  ASSERT(DwVfpRegister::NumReservedRegisters() == 2);
+  if (CpuFeatures::IsSupported(VFP32DREGS)) {
+    vstm(db_w, sp, d16, d31);
   }
+  vstm(db_w, sp, d0, d13);
 }
 
 
 void MacroAssembler::PopSafepointRegistersAndDoubles() {
   // Number of d-regs not known at snapshot time.
   ASSERT(!Serializer::enabled());
-  for (int i = 0; i < DwVfpRegister::NumAllocatableRegisters(); i++) {
-    vldr(DwVfpRegister::FromAllocationIndex(i), sp, i * kDoubleSize);
+  // Only save allocatable registers.
+  ASSERT(kScratchDoubleReg.is(d15) && kDoubleRegZero.is(d14));
+  ASSERT(DwVfpRegister::NumReservedRegisters() == 2);
+  vldm(ia_w, sp, d0, d13);
+  if (CpuFeatures::IsSupported(VFP32DREGS)) {
+    vldm(ia_w, sp, d16, d31);
   }
-  add(sp, sp, Operand(DwVfpRegister::NumAllocatableRegisters() *
-                      kDoubleSize));
   PopSafepointRegisters();
 }