Refactor FrameAndConstantPoolScope and ConstantPoolUnavailableScope to be architecture independent

src/macro-assembler.h

Index: src/macro-assembler.h
diff --git a/src/macro-assembler.h b/src/macro-assembler.h
index 54cebca90f879fed0bb4e74aa737014704b6bbd4..ae2a39be4b2d78728099e324878db24fb0d848b3 100644
--- a/src/macro-assembler.h
+++ b/src/macro-assembler.h
@@ -93,10 +93,12 @@ namespace internal {
 
 class FrameScope {
  public:
-  explicit FrameScope(MacroAssembler* masm, StackFrame::Type type)
+  explicit FrameScope(MacroAssembler* masm, StackFrame::Type type,
+                      bool enter_frame = true)

[rmcilroy, 2014/09/26 15:54:57]

I don't like this default argument. Rethinking this I think we should avoid
making FrameAndConstantPoolScope a subclass of FrameScope.  It doesn't buy us
much and there are subtle ordering constraints (like set_constant_pool_available
having to happen before masm->EnterFrame and after LeaveFrame) which are
difficult to ensure with this class inheritance. 

[baixo, 2014/10/02 09:18:21]

I was worried about code duplication, since this class is very similar to
FrameScope. But yes, the subclass approach will only work if the ordering
changes are not an issue. I reverted back to the original
FrameAndConstantPoolScope class.

       : masm_(masm), type_(type), old_has_frame_(masm->has_frame()) {
     masm->set_has_frame(true);
-    if (type != StackFrame::MANUAL && type_ != StackFrame::NONE) {
+    if (enter_frame && type != StackFrame::MANUAL &&
+        type_ != StackFrame::NONE) {
       masm->EnterFrame(type);
     }
   }
@@ -118,12 +120,34 @@ class FrameScope {
     masm_->LeaveFrame(type_);
   }
 
- private:
+ protected:
   MacroAssembler* masm_;
   StackFrame::Type type_;
   bool old_has_frame_;
 };
 
+class FrameAndConstantPoolScope : public FrameScope {
+ public:
+  FrameAndConstantPoolScope(MacroAssembler* masm, StackFrame::Type type)
+      : FrameScope(masm, type, false),
+        old_constant_pool_available_(masm->is_constant_pool_available()) {
+    // We only want to enable constant pool access for non-manual frame scopes
+    // to ensure the constant pool pointer is valid throughout the scope.
+    DCHECK(type_ != StackFrame::MANUAL && type_ != StackFrame::NONE);
+    masm->set_constant_pool_available(true);
+    masm->EnterFrame(type, !old_constant_pool_available_);
+  }
+
+  ~FrameAndConstantPoolScope() {
+    masm_->set_constant_pool_available(old_constant_pool_available_);
+  }
+
+ private:
+  bool old_constant_pool_available_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(FrameAndConstantPoolScope);
+};
+
 
 class AllowExternalCallThatCantCauseGC: public FrameScope {
  public: