Lock unused input varnodes with special flag, not typelock

Author: caheckman

Ghidra/Features/Decompiler/src/decompile/cpp/coreaction.cc

@@ -3469,6 +3469,7 @@ int4 ActionPrototypeTypes::apply(Funcdata &data)
       ProtoParameter *param = data.getFuncProto().getParam(i);
       Varnode *vn = data.newVarnode( param->getSize(), param->getAddress());
       vn = data.setInputVarnode(vn);
+      vn->setLockedInput();
       if (topbl != (BlockBasic *)0)
 	extendInput(data,vn,param,topbl);
       if (ptr_size > 0) {

Ghidra/Features/Decompiler/src/decompile/cpp/funcdata_varnode.cc

@@ -711,12 +711,9 @@ void Funcdata::clearDeadVarnodes(void)
   while(iter!=vbank.endLoc()) {
     vn = *iter++;
     if (vn->hasNoDescend()) {
-      if (vn->isInput()&&(!vn->isMark())) {
-	if ((vn->isSpacebase())|| // Space base is always typelocked
-	    (!vn->isTypeLock())) {
-	  vbank.makeFree(vn);
-	  vn->clearCover();
-	}
+      if (vn->isInput() && !vn->isLockedInput()) {
+	vbank.makeFree(vn);
+	vn->clearCover();
       }
       if (vn->isFree())
 	vbank.destroy(vn);

Ghidra/Features/Decompiler/src/decompile/cpp/varnode.hh

@@ -116,7 +116,8 @@ public:
     ptrcheck = 0x10,	        ///< The Varnode value is \e NOT a pointer
     ptrflow = 0x20,             ///< If this varnode flows to or from a pointer
     unsignedprint = 0x40,	///< Constant that must be explicitly printed as unsigned
-    stack_store = 0x80		///< Created by an explicit STORE
+    stack_store = 0x80,		///< Created by an explicit STORE
+    locked_input = 0x100	///< Input that exists even if its unused
   };
 private:
   mutable uint4 flags;		///< The collection of boolean attributes for this Varnode
@@ -237,6 +238,7 @@ public:
   bool isMark(void) const { return ((flags&Varnode::mark)!=0); } ///< Has \b this been visited by the current algorithm?
   bool isActiveHeritage(void) const { return ((addlflags&Varnode::activeheritage)!=0); } ///< Is \b this currently being traced by the Heritage algorithm?
   bool isStackStore(void) const { return ((addlflags&Varnode::stack_store)!=0); } ///< Was this originally produced by an explicit STORE
+  bool isLockedInput(void) const { return ((addlflags&Varnode::locked_input)!=0); }	///< Is always an input, even if unused
 
   /// Is \b this just a special placeholder representing INDIRECT creation?
   bool isIndirectZero(void) const { return ((flags&(Varnode::indirect_creation|Varnode::constant))==(Varnode::indirect_creation|Varnode::constant)); }
@@ -297,6 +299,7 @@ public:
   void setUnsignedPrint(void) { addlflags |= Varnode::unsignedprint; } ///< Force \b this to be printed as unsigned
   bool updateType(Datatype *ct,bool lock,bool override); ///< (Possibly) set the Datatype given various restrictions
   void setStackStore(void) { addlflags |= Varnode::stack_store; } ///< Mark as produced by explicit CPUI_STORE
+  void setLockedInput(void) { addlflags |= Varnode::locked_input; }	///< Mark as existing input, even if unused
   void copySymbol(const Varnode *vn); ///< Copy symbol info from \b vn
   void copySymbolIfValid(const Varnode *vn);	///< Copy symbol info from \b vn if constant value matches
   Datatype *getLocalType(void) const; ///< Calculate type of Varnode based on local information