Revert of [regexp] Remove remainder of native RegExpExecStub

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

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/regexp/ppc/regexp-macro-assembler-ppc.h"
 
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
@@ skipping 20 matching lines @@
  * - r30: End of input (points to byte after last character in input).
  * - r31: Frame pointer. Used to access arguments, local variables and
  *         RegExp registers.
  * - r12: IP register, used by assembler. Very volatile.
  * - r1/sp : Points to tip of C stack.
  *
  * The remaining registers are free for computations.
  * Each call to a public method should retain this convention.
  *
  * The stack will have the following structure:
- *  - fp[40]  Isolate* isolate   (address of the current isolate)
+ *  - fp[44]  Isolate* isolate   (address of the current isolate)
+ *  - fp[40]  secondary link/return address used by native call.
  *  - fp[36]  lr save area (currently unused)
  *  - fp[32]  backchain    (currently unused)
  *  --- sp when called ---
  *  - fp[28]  return address     (lr).
  *  - fp[24]  old frame pointer  (r31).
  *  - fp[0..20]  backup of registers r25..r30
  *  --- frame pointer ----
  *  - fp[-4]  direct_call        (if 1, direct call from JavaScript code,
  *                                if 0, call through the runtime system).
  *  - fp[-8]  stack_area_base    (high end of the memory area to use as
@@ skipping 21 matching lines @@
  * character of the string). The remaining registers start out as garbage.
  *
  * 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,
- *              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 ppc/simulator-ppc.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_)
 
 RegExpMacroAssemblerPPC::RegExpMacroAssemblerPPC(Isolate* isolate, Zone* zone,
                                                  Mode mode,
                                                  int registers_to_save)
     : NativeRegExpMacroAssembler(isolate, zone),
       masm_(new MacroAssembler(isolate, NULL, kRegExpCodeSize,
                                CodeObjectRequired::kYes)),
@@ skipping 1222 matching lines @@
 }
 
 
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_PPC