ARM: Make use of d16-d31 when available.

src/arm/code-stubs-arm.h

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
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@@ skipping 454 matching lines @@
 
     // If we have to call into C then we need to save and restore all caller-
     // saved registers that were not already preserved.  The scratch registers
     // will be restored by other means so we don't bother pushing them here.
     void SaveCallerSaveRegisters(MacroAssembler* masm, SaveFPRegsMode mode) {
       masm->stm(db_w, sp, (kCallerSaved | lr.bit()) & ~scratch1_.bit());
       if (mode == kSaveFPRegs) {
         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--) {
+        // XXX: Why is d0 special? It's not the scratch register..

[Rodolph Perfetta, 2012/12/05 00:42:10]

A long time ago, d0 was the scratch register, so this may be a remain from this
time. This method is currently saving callee saved register too.

[hans, 2012/12/05 14:12:58]

So I guess what we want here is to save d0--d7, and d16--d31 when available?
(Same below)

+        for (int i = DwVfpRegister::NumAvailableRegisters() - 1; i > 0; i--) {
           DwVfpRegister reg = DwVfpRegister::from_code(i);
           masm->vstr(reg, MemOperand(sp, (i - 1) * kDoubleSize));
         }
       }
     }
 
     inline void RestoreCallerSaveRegisters(MacroAssembler*masm,
                                            SaveFPRegsMode mode) {
       if (mode == kSaveFPRegs) {
         CpuFeatures::Scope scope(VFP2);
         // Restore all VFP registers except d0.
-        for (int i = DwVfpRegister::kNumRegisters - 1; i > 0; i--) {
+        // XXX: Why is d0 special? It's not the scratch register..

[Rodolph Perfetta, 2012/12/05 00:42:10]

Ditto.

+        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());
     }
 
     inline Register object() { return object_; }
     inline Register address() { return address_; }
     inline Register scratch0() { return scratch0_; }
     inline Register scratch1() { return scratch1_; }
 
    private:
@@ skipping 279 matching lines @@
 
   class LookupModeBits: public BitField<LookupMode, 0, 1> {};
 
   LookupMode mode_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_CODE_STUBS_ARM_H_