X64: Optimize access to external references.

src/x64/regexp-macro-assembler-x64.cc

Index: src/x64/regexp-macro-assembler-x64.cc
diff --git a/src/x64/regexp-macro-assembler-x64.cc b/src/x64/regexp-macro-assembler-x64.cc
index 37d93cc53d5bb69840c534a86e2ed6fd11f5c291..bd398cc6c31a530bda47428faada139d34fc03d7 100644
--- a/src/x64/regexp-macro-assembler-x64.cc
+++ b/src/x64/regexp-macro-assembler-x64.cc
@@ -63,6 +63,8 @@ namespace internal {
  *
  * The registers rax, rbx, r9 and r11 are free to use for computations.
  * If changed to use r12+, they should be saved as callee-save registers.
+ * The macro assembler special registers r12 and r13 (kSmiConstantRegister,
+ * kRootRegister) are not initialized during RegExp code.

[William Hesse, 2011/03/22 14:05:08]

"are not initialized" is confusing.  Do you mean "free for general purpose use
during RegExp code"?

[Lasse Reichstein, 2011/03/22 14:12:21]

Except that they are not free either (since we don't save them and they are
callee-save).
Rewording.

  *
  * Each call to a C++ method should retain these registers.
  *
@@ -111,6 +113,7 @@ RegExpMacroAssemblerX64::RegExpMacroAssemblerX64(
     Mode mode,
     int registers_to_save)
     : masm_(new MacroAssembler(NULL, kRegExpCodeSize)),
+      no_root_array_scope_(masm_),
       code_relative_fixup_positions_(4),
       mode_(mode),
       num_registers_(registers_to_save),