Revert of [regexp] Remove remainder of native RegExpExecStub

src/regexp/s390/regexp-macro-assembler-s390.cc

Index: src/regexp/s390/regexp-macro-assembler-s390.cc
diff --git a/src/regexp/s390/regexp-macro-assembler-s390.cc b/src/regexp/s390/regexp-macro-assembler-s390.cc
index 7b8ac8e24eb8e4175f2b53890c51044d5e726d5e..d927a110b9ea696cc54316d03160e76a6086e7b0 100644
--- a/src/regexp/s390/regexp-macro-assembler-s390.cc
+++ b/src/regexp/s390/regexp-macro-assembler-s390.cc
@@ -39,7 +39,8 @@
  * Each call to a public method should retain this convention.
  *
  * The stack will have the following structure:
- *  - fp[108] Isolate* isolate   (address of the current isolate)
+ *  - fp[112] Isolate* isolate   (address of the current isolate)
+ *  - fp[108] secondary link/return address used by native call.
  *  - fp[104] direct_call        (if 1, direct call from JavaScript code,
  *                                if 0, call through the runtime system).
  *  - fp[100] stack_area_base    (high end of the memory area to use as
@@ -82,13 +83,16 @@
  *              Address start,
  *              Address end,
  *              int* capture_output_array,
- *              int num_capture_registers,
  *              byte* stack_area_base,
- *              bool direct_call = false,
- *              Isolate* isolate);
+ *              Address secondary_return_address,  // Only used by native call.
+ *              bool direct_call = false)
  * The call is performed by NativeRegExpMacroAssembler::Execute()
  * (in regexp-macro-assembler.cc) via the CALL_GENERATED_REGEXP_CODE macro
  * in s390/simulator-s390.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_)