ARM: Add comments to clarify conditionally executed code dealing with d16-d31

src/arm/deoptimizer-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 993 matching lines @@
   if (CpuFeatures::IsSupported(VFP2)) {
     CpuFeatures::Scope scope(VFP2);
     // Save all allocatable VFP registers before messing with them.
     ASSERT(kDoubleRegZero.code() == 14);
     ASSERT(kScratchDoubleReg.code() == 15);
 
     // Check CPU flags for number of registers, setting the Z condition flag.
     __ CheckFor32DRegs(ip);
 
     // Push registers d0-d13, and possibly d16-d31, on the stack.
+    // If d16-d31 are not pushed, decrease the stack pointer instead.
     __ vstm(db_w, sp, d16, d31, ne);
     __ sub(sp, sp, Operand(16 * kDoubleSize), LeaveCC, eq);
     __ vstm(db_w, sp, d0, d13);
   } else {
     __ sub(sp, sp, Operand(kDoubleRegsSize));
   }
 
   // Push all 16 registers (needed to populate FrameDescription::registers_).
   // TODO(1588) Note that using pc with stm is deprecated, so we should perhaps
   // handle this a bit differently.
@@ skipping 201 matching lines @@
     __ push(ip);
     __ b(&done);
     ASSERT(masm()->pc_offset() - start == table_entry_size_);
   }
   __ bind(&done);
 }
 
 #undef __
 
 } }  // namespace v8::internal