Implement initblk in the interpreter

Author: kg

src/coreclr/interpreter/compiler.cpp

@@ -5623,6 +5623,21 @@ void InterpCompiler::GenerateCode(CORINFO_METHOD_INFO* methodInfo)
                         m_ip += 5;
                         break;
                     }
+                    case CEE_INITBLK:
+                    {
+                        if (volatile_)
+                        {
+                            AddIns(INTOP_MEMBAR);
+                            volatile_ = false;
+                        }
+
+                        CHECK_STACK(3);
+                        AddIns(INTOP_INITBLK);
+                        m_pStackPointer -= 3;
+                        m_pLastNewIns->SetSVars3(m_pStackPointer[0].var, m_pStackPointer[1].var, m_pStackPointer[2].var);
+                        m_ip++;
+                        break;
+                    }
                     case CEE_CPBLK:
                         CHECK_STACK(3);
                         if (volatile_)

src/coreclr/interpreter/intops.def

@@ -397,6 +397,7 @@ OPDEF(INTOP_GENERICLOOKUP, "generic", 4, 1, 1, InterpOpGenericLookup)
 OPDEF(INTOP_CALL_FINALLY, "call.finally", 2, 0, 0, InterpOpBranch)
 
 OPDEF(INTOP_ZEROBLK_IMM, "zeroblk.imm", 3, 0, 1, InterpOpInt)
+OPDEF(INTOP_INITBLK, "initblk", 4, 0, 3, InterpOpNoArgs)
 OPDEF(INTOP_CPBLK, "cpblk", 4, 0, 3, InterpOpNoArgs)
 OPDEF(INTOP_LOCALLOC, "localloc", 3, 1, 1, InterpOpNoArgs)
 OPDEF(INTOP_BREAKPOINT, "breakpoint", 1, 0, 0, InterpOpNoArgs)

src/coreclr/vm/interpexec.cpp

@@ -2172,6 +2172,18 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
                     ip += 4;
                     break;
                 }
+                case INTOP_INITBLK:
+                {
+                    void* dst = LOCAL_VAR(ip[1], void*);
+                    uint8_t value = LOCAL_VAR(ip[2], uint8_t);
+                    uint32_t size = LOCAL_VAR(ip[3], uint32_t);
+                    if (size && !dst)
+                        COMPlusThrow(kNullReferenceException);
+                    else
+                        memset(dst, value, size);
+                    ip += 4;
+                    break;
+                }
                 case INTOP_LOCALLOC:
                 {
                     size_t len = LOCAL_VAR(ip[2], size_t);