arch-arm: Disassemble A64 ISB with 4-bit Crm imm

ISB takes a 4-bit Crm operand that defaults to gem5#15. Print it if
it has the non-default value.

Change-Id: I4655a9adf58745c15d2abc8333601e72a93f654e

Author: bpfoley

src/arch/arm/insts/misc64.cc

@@ -2643,4 +2643,15 @@ AtOp64::addressTranslation64(ThreadContext* tc,
     return std::make_pair(fault, par);
 }
 
+std::string
+IsbOp64::generateDisassembly(Addr pc, const loader::SymbolTable *symtab) const
+{
+    std::stringstream ss;
+    printMnemonic(ss, "", false);
+    if (imm != 15) {
+        ccprintf(ss, "#%d", imm);
+    }
+    return ss.str();
+}
+
 } // namespace gem5

src/arch/arm/insts/misc64.hh

@@ -357,6 +357,20 @@ class AtOp64 : public MiscRegRegImmOp64
         BaseMMU::Mode mode, Request::Flags flags, RegVal val) const;
 };
 
+class IsbOp64 : public ArmISA::ArmStaticInst
+{
+  protected:
+    uint64_t imm;
+
+    IsbOp64(const char *mnem, ArmISA::ExtMachInst _machInst,
+            OpClass __opClass, uint64_t _imm) :
+        ArmISA::ArmStaticInst(mnem, _machInst, __opClass), imm(_imm)
+    {}
+
+    std::string generateDisassembly(
+            Addr pc, const loader::SymbolTable *symtab) const override;
+};
+
 } // namespace gem5
 
 #endif

src/arch/arm/isa/formats/aarch64.isa

@@ -428,7 +428,7 @@ namespace Aarch64
                           case 0x5:
                             return new Dmb64(machInst);
                           case 0x6:
-                            return new Isb64(machInst);
+                            return new Isb64(machInst, crm);
                           default:
                             return new Unknown64(machInst);
                         }

src/arch/arm/isa/insts/misc64.isa

@@ -188,10 +188,10 @@ let {{
     decoder_output += BasicConstructor64.subst(unknown64Iop)
     exec_output += BasicExecute.subst(unknown64Iop)
 
-    isbIop = ArmInstObjParams("isb", "Isb64", "ArmStaticInst", "",
+    isbIop = ArmInstObjParams("isb", "Isb64", "IsbOp64", "",
                               ['IsSquashAfter'])
-    header_output += BasicDeclare.subst(isbIop)
-    decoder_output += BasicConstructor64.subst(isbIop)
+    header_output += ImmOp64Declare.subst(isbIop)
+    decoder_output += ImmOp64Constructor.subst(isbIop)
     exec_output += BasicExecute.subst(isbIop)
 
     dsbLocalIop = ArmInstObjParams("dsb", "Dsb64Local", "ArmStaticInst", "",