X87: Experimental support for RegExp lookbehind.

  port 906903ac (r32043)

  original commit message:

BUG=

Review URL: https://codereview.chromium.org/1453303003

Cr-Commit-Position: refs/heads/master@{#32069}

src/regexp/x87/regexp-macro-assembler-x87.h

@@ -33,9 +33,11 @@ class RegExpMacroAssemblerX87: public NativeRegExpMacroAssembler {
   // A "greedy loop" is a loop that is both greedy and with a simple
   // body. It has a particularly simple implementation.
   virtual void CheckGreedyLoop(Label* on_tos_equals_current_position);
-  virtual void CheckNotAtStart(Label* on_not_at_start);
-  virtual void CheckNotBackReference(int start_reg, Label* on_no_match);
+  virtual void CheckNotAtStart(int cp_offset, Label* on_not_at_start);
+  virtual void CheckNotBackReference(int start_reg, bool read_backward,
+                                     Label* on_no_match);
   virtual void CheckNotBackReferenceIgnoreCase(int start_reg,
+                                               bool read_backward,
                                                Label* on_no_match);
   virtual void CheckNotCharacter(uint32_t c, Label* on_not_equal);
   virtual void CheckNotCharacterAfterAnd(uint32_t c,
@@ -116,9 +118,9 @@ class RegExpMacroAssemblerX87: public NativeRegExpMacroAssembler {
   static const int kBackup_edi = kBackup_esi - kPointerSize;
   static const int kBackup_ebx = kBackup_edi - kPointerSize;
   static const int kSuccessfulCaptures = kBackup_ebx - kPointerSize;
-  static const int kInputStartMinusOne = kSuccessfulCaptures - kPointerSize;
+  static const int kStringStartMinusOne = kSuccessfulCaptures - kPointerSize;
   // First register address. Following registers are below it on the stack.
-  static const int kRegisterZero = kInputStartMinusOne - kPointerSize;
+  static const int kRegisterZero = kStringStartMinusOne - kPointerSize;
 
   // Initial size of code buffer.
   static const size_t kRegExpCodeSize = 1024;