Revert of [regexp] Remove remainder of native RegExpExecStub

src/regexp/arm64/regexp-macro-assembler-arm64.cc

Index: src/regexp/arm64/regexp-macro-assembler-arm64.cc
diff --git a/src/regexp/arm64/regexp-macro-assembler-arm64.cc b/src/regexp/arm64/regexp-macro-assembler-arm64.cc
index d4b80a7c3f59df4936281c69cb176d0514990b26..7d015d096b2540ad40ff3e9e62637b453be41956 100644
--- a/src/regexp/arm64/regexp-macro-assembler-arm64.cc
+++ b/src/regexp/arm64/regexp-macro-assembler-arm64.cc
@@ -56,7 +56,10 @@
  *              (as referred to in
  *              the code)
  *
- *  - fp[96]   isolate            Address of the current isolate.
+ *  - fp[104]   isolate            Address of the current isolate.
+ *  - fp[96]    return_address     Secondary link/return address
+ *                                 used by an exit frame if this is a
+ *                                 native call.
  *  ^^^ csp when called ^^^
  *  - fp[88]    lr                 Return from the RegExp code.
  *  - fp[80]    r29                Old frame pointer (CalleeSaved).
@@ -86,18 +89,23 @@
  * The data up to the return address must be placed there by the calling
  * code and the remaining arguments are passed in registers, e.g. by calling the
  * code entry as cast to a function with the signature:
- * int (*match)(String* input_string,
- *              int start_index,
- *              Address start,
- *              Address end,
- *              int* capture_output_array,
- *              int num_capture_registers,
- *              byte* stack_area_base,
+ * int (*match)(String* input,
+ *              int start_offset,
+ *              Address input_start,
+ *              Address input_end,
+ *              int* output,
+ *              int output_size,
+ *              Address stack_base,
  *              bool direct_call = false,
- *              Isolate* isolate);
+ *              Address secondary_return_address,  // Only used by native call.
+ *              Isolate* isolate)
  * The call is performed by NativeRegExpMacroAssembler::Execute()
  * (in regexp-macro-assembler.cc) via the CALL_GENERATED_REGEXP_CODE macro
  * in arm64/simulator-arm64.h.
+ * When calling as a non-direct call (i.e., from C++ code), the return address
+ * area is overwritten with the LR register by the RegExp code. When doing a
+ * direct call from generated code, the return address is placed there by
+ * the calling code, as in a normal exit frame.
  */
 
 #define __ ACCESS_MASM(masm_)