arch: Promote instReady to the base InstDecoder class.

Move the instDone flag, and the instReady function which was
consistently implemented just to return it, to the base InstDecoder
class. This flag can still be accessed easily from the subclasses, but
now it can be retrieved with just an InstDecoder pointer without a
virtual function call.

Change-Id: I8c662aa01da8fe33ffe679071c701e0aadc1a795
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52072
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/decoder.hh

@@ -66,7 +66,6 @@ class Decoder : public InstDecoder
     ExtMachInst emi;
     uint32_t data;
     bool bigThumb;
-    bool instDone;
     bool outOfBytes;
     int offset;
     bool foundIt;
@@ -146,16 +145,6 @@ class Decoder : public InstDecoder
      */
     bool needMoreBytes() const { return outOfBytes; }
 
-    /**
-     * Is an instruction ready to be decoded?
-     *
-     * CPU models call this method to determine if decode() will
-     * return a new instruction on the next call. It typically only
-     * returns false if the decoder hasn't received enough data to
-     * decode a full instruction.
-     */
-    bool instReady() const { return instDone; }
-
     /**
      * Feed data to the decoder.
      *

src/arch/generic/decoder.hh

@@ -43,6 +43,8 @@ class InstDecoder
     size_t _moreBytesSize;
     Addr _pcMask;
 
+    bool instDone = false;
+
   public:
     template <typename MoreBytesType>
     InstDecoder(MoreBytesType *mb_buf) :
@@ -56,6 +58,16 @@ class InstDecoder
     void *moreBytesPtr() const { return _moreBytesPtr; }
     size_t moreBytesSize() const { return _moreBytesSize; }
     Addr pcMask() const { return _pcMask; }
+
+    /**
+     * Is an instruction ready to be decoded?
+     *
+     * CPU models call this method to determine if decode() will
+     * return a new instruction on the next call. It typically only
+     * returns false if the decoder hasn't received enough data to
+     * decode a full instruction.
+     */
+    bool instReady() const { return instDone; }
 };
 
 } // namespace gem5

src/arch/mips/decoder.hh

@@ -50,10 +50,9 @@ class Decoder : public InstDecoder
     //The extended machine instruction being generated
     ExtMachInst emi;
     uint32_t machInst;
-    bool instDone;
 
   public:
-    Decoder(ISA* isa = nullptr) : InstDecoder(&machInst), instDone(false)
+    Decoder(ISA* isa = nullptr) : InstDecoder(&machInst)
     {}
 
     void
@@ -82,12 +81,6 @@ class Decoder : public InstDecoder
         return true;
     }
 
-    bool
-    instReady()
-    {
-        return instDone;
-    }
-
     void takeOverFrom(Decoder *old) {}
 
   protected:

src/arch/power/decoder.hh

@@ -48,10 +48,9 @@ class Decoder : public InstDecoder
   protected:
     // The extended machine instruction being generated
     ExtMachInst emi;
-    bool instDone;
 
   public:
-    Decoder(ISA* isa=nullptr) : InstDecoder(&emi), instDone(false) {}
+    Decoder(ISA* isa=nullptr) : InstDecoder(&emi) {}
 
     void
     process()
@@ -79,12 +78,6 @@ class Decoder : public InstDecoder
         return true;
     }
 
-    bool
-    instReady()
-    {
-        return instDone;
-    }
-
     void takeOverFrom(Decoder *old) {}
 
   protected:

src/arch/riscv/decoder.hh

@@ -57,7 +57,6 @@ class Decoder : public InstDecoder
     //The extended machine instruction being generated
     ExtMachInst emi;
     uint32_t machInst;
-    bool instDone;
 
     StaticInstPtr decodeInst(ExtMachInst mach_inst);
 
@@ -79,7 +78,6 @@ class Decoder : public InstDecoder
     void moreBytes(const PCStateBase &pc, Addr fetchPC);
 
     bool needMoreBytes() { return more; }
-    bool instReady() { return instDone; }
     void takeOverFrom(Decoder *old) {}
 
     StaticInstPtr decode(PCStateBase &nextPC);

src/arch/sparc/decoder.hh

@@ -48,11 +48,10 @@ class Decoder : public InstDecoder
     // The extended machine instruction being generated
     ExtMachInst emi;
     uint32_t machInst;
-    bool instDone;
     RegVal asi;
 
   public:
-    Decoder(ISA* isa=nullptr) : InstDecoder(&machInst), instDone(false), asi(0)
+    Decoder(ISA* isa=nullptr) : InstDecoder(&machInst), asi(0)
     {}
 
     void process() {}
@@ -89,12 +88,6 @@ class Decoder : public InstDecoder
         return true;
     }
 
-    bool
-    instReady()
-    {
-        return instDone;
-    }
-
     void
     setContext(RegVal _asi)
     {

src/arch/x86/decoder.hh

@@ -176,8 +176,6 @@ class Decoder : public InstDecoder
   protected:
     // Whether or not we're out of bytes.
     bool outOfBytes = true;
-    // Whether we've completed generating an ExtMachInst.
-    bool instDone = false;
     // The size of the displacement value.
     int displacementSize;
     // The size of the immediate value.
@@ -324,7 +322,6 @@ class Decoder : public InstDecoder
     }
 
     bool needMoreBytes() { return outOfBytes; }
-    bool instReady() { return instDone; }
 
     void
     updateNPC(X86ISA::PCState &nextPC)