[torque] hide internal variables used for labels with parameters

This fixes a bug that the variables used to implement labels with
parameters in CSA leak into the user-accessible scope.

Example:

macro Foo() labels Bar(Smi) {
  Bar0 = 5;
}

Bug: v8:7793
Change-Id: I33bf5a207c7e9e7337fa79fc7591c05901b2fa5b
Reviewed-on: https://chromium-review.googlesource.com/1246183Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56257}

src/torque/declaration-visitor.cc

@@ -638,7 +638,8 @@ void DeclarationVisitor::DeclareSignature(const Signature& signature) {
       }
 
       std::string var_name = label.name + std::to_string(i++);
-      new_label->AddVariable(DeclareVariable(var_name, var_type, false));
+      new_label->AddVariable(
+          declarations()->CreateVariable(var_name, var_type, false));
     }
   }
 }

src/torque/declarations.cc

@@ -304,6 +304,15 @@ RuntimeFunction* Declarations::DeclareRuntimeFunction(
   return result;
 }
 
+Variable* Declarations::CreateVariable(const std::string& var, const Type* type,
+                                       bool is_const) {
+  std::string name(var + "_" +
+                   std::to_string(GetNextUniqueDeclarationNumber()));
+  std::replace(name.begin(), name.end(), '.', '_');
+  return RegisterDeclarable(
+      std::unique_ptr<Variable>(new Variable(var, name, type, is_const)));
+}
+
 Variable* Declarations::DeclareVariable(const std::string& var,
                                         const Type* type, bool is_const) {
   std::string name(var + "_" +

src/torque/declarations.h

@@ -91,6 +91,8 @@ class Declarations {
   RuntimeFunction* DeclareRuntimeFunction(const std::string& name,
                                           const Signature& signature);
 
+  Variable* CreateVariable(const std::string& var, const Type* type,
+                           bool is_const);
   Variable* DeclareVariable(const std::string& var, const Type* type,
                             bool is_const);