cpu: Use a unique_ptr to manage cached disassembly.

This is a fairly minor improvement, but avoids having to manually keep
track of that string pointer.

Change-Id: Ic3d4ddd9445920a110b36ab0cd64ff2289cf0139
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42967
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>

src/arch/mips/isa/formats/branch.isa

@@ -153,14 +153,11 @@ output decoder {{
     PCDependentDisassembly::disassemble(
             Addr pc, const Loader::SymbolTable *symtab) const
     {
-        if (!cachedDisassembly ||
-            pc != cachedPC || symtab != cachedSymtab)
-        {
-            if (cachedDisassembly)
-                delete cachedDisassembly;
+        if (!cachedDisassembly || pc != cachedPC || symtab != cachedSymtab) {
+            if (!cachedDisassembly)
+                cachedDisassembly.reset(new std::string);
 
-            cachedDisassembly =
-                new std::string(generateDisassembly(pc, symtab));
+            *cachedDisassembly = generateDisassembly(pc, symtab);
             cachedPC = pc;
             cachedSymtab = symtab;
         }

src/arch/power/insts/branch.cc

@@ -37,14 +37,11 @@ const std::string &
 PCDependentDisassembly::disassemble(
         Addr pc, const Loader::SymbolTable *symtab) const
 {
-    if (!cachedDisassembly ||
-        pc != cachedPC || symtab != cachedSymtab)
-    {
-        if (cachedDisassembly)
-            delete cachedDisassembly;
+    if (!cachedDisassembly || pc != cachedPC || symtab != cachedSymtab) {
+        if (!cachedDisassembly)
+            cachedDisassembly.reset(new std::string);
 
-        cachedDisassembly =
-            new std::string(generateDisassembly(pc, symtab));
+        *cachedDisassembly = generateDisassembly(pc, symtab);
         cachedPC = pc;
         cachedSymtab = symtab;
     }

src/cpu/static_inst.cc

@@ -64,12 +64,6 @@ class NopStaticInst : public StaticInst
 StaticInstPtr StaticInst::nullStaticInstPtr;
 StaticInstPtr StaticInst::nopStaticInstPtr = new NopStaticInst;
 
-StaticInst::~StaticInst()
-{
-    if (cachedDisassembly)
-        delete cachedDisassembly;
-}
-
 bool
 StaticInst::hasBranchTarget(const TheISA::PCState &pc, ThreadContext *tc,
                             TheISA::PCState &tgt) const
@@ -111,8 +105,10 @@ StaticInst::branchTarget(ThreadContext *tc) const
 const std::string &
 StaticInst::disassemble(Addr pc, const Loader::SymbolTable *symtab) const
 {
-    if (!cachedDisassembly)
-        cachedDisassembly = new std::string(generateDisassembly(pc, symtab));
+    if (!cachedDisassembly) {
+        cachedDisassembly =
+            std::make_unique<std::string>(generateDisassembly(pc, symtab));
+    }
 
     return *cachedDisassembly;
 }

src/cpu/static_inst.hh

@@ -283,7 +283,7 @@ class StaticInst : public RefCounted, public StaticInstFlags
      * String representation of disassembly (lazily evaluated via
      * disassemble()).
      */
-    mutable std::string *cachedDisassembly = nullptr;
+    mutable std::unique_ptr<std::string> cachedDisassembly;
 
     /**
      * Internal function to generate disassembly string.
@@ -301,7 +301,7 @@ class StaticInst : public RefCounted, public StaticInstFlags
     {}
 
   public:
-    virtual ~StaticInst();
+    virtual ~StaticInst() {};
 
     virtual Fault execute(ExecContext *xc,
             Trace::InstRecord *traceData) const = 0;