A64: Preserve/restore the FP registers in the exit frame when required.

src/a64/macro-assembler-a64.h

 // Copyright 2013 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 1475 matching lines @@
   // AllocationSiteInfo support. Arrays may have an associated
   // AllocationSiteInfo object that can be checked for in order to pretransition
   // to another type.
   // On entry, receiver should point to the array object.
   // If allocation info is present, the Z flag is set (so that the eq
   // condition will pass).
   void TestJSArrayForAllocationSiteInfo(Register receiver,
                                         Register scratch1,
                                         Register scratch2);
 
+  // The stack pointer has to switch between csp and jssp when setting up and
+  // destroying the exit frame. Hence preserving/restoring the registers is
+  // slightly more complicated than simple push/pop operations.
+  void ExitFramePreserveFPRegs();
+  void ExitFrameRestoreFPRegs();
+
   // Enter exit frame. Exit frames are used when calling C code from generated
   // (JavaScript) code.
   //
   // The stack pointer must be jssp on entry, and will be set to csp by this
   // function. The frame pointer is also configured, but the only other
   // registers modified by this function are the provided scratch register, and
   // jssp.
   //
   // The 'extra_space' argument can be used to allocate some space in the exit
   // frame that will be ignored by the GC. This space will be reserved in the
   // bottom of the frame immediately above the return address slot.
   //
   // Set up a stack frame and registers as follows:
   //         fp[8]: CallerPC (lr)
   //   fp -> fp[0]: CallerFP (old fp)
   //         fp[-8]: SPOffset (new csp)
   //         fp[-16]: CodeObject()
-  //         csp[...]: Saved doubles, if saved_doubles is true.
+  //         fp[-16 - fp-size]: Saved doubles, if saved_doubles is true.
   //         csp[8]: Memory reserved for the caller if extra_space != 0.
   //                 Alignment padding, if necessary.
   //  csp -> csp[0]: Space reserved for the return address.
   //
   // This function also stores the new frame information in the top frame, so
   // that the new frame becomes the current frame.
   void EnterExitFrame(bool save_doubles,
                       const Register& scratch,
                       int extra_space = 0);
 
@@ skipping 586 matching lines @@
 #error "Unsupported option"
 #define CODE_COVERAGE_STRINGIFY(x) #x
 #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 #endif  // V8_A64_MACRO_ASSEMBLER_A64_H_