implement missing apis

sources/LLVMSharp/Extensions/LLVMTargetRef.cs

@@ -69,5 +69,15 @@ public string Name
         public override int GetHashCode() => Pointer.GetHashCode();
 
         public LLVMTargetRef GetNext() => LLVM.GetNextTarget(this);
+
+        public LLVMTargetMachineRef CreateTargetMachine(string triple, string cpu, string features, LLVMCodeGenOptLevel level, LLVMRelocMode reloc, LLVMCodeModel codeModel)
+        {
+            using (var marshaledTriple = new MarshaledString(triple))
+            using (var marshaledCPU = new MarshaledString(cpu))
+            using (var marshaledFeatures = new MarshaledString(features))
+            {
+                return LLVM.CreateTargetMachine(this, marshaledTriple, marshaledCPU, marshaledFeatures, level, reloc, codeModel);
+            }
+        }
     }
 }

sources/LLVMSharp/Wrappers/LLVMTargetMachineRef.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 
 namespace LLVMSharp
 {
@@ -20,5 +21,49 @@ public static implicit operator LLVMTargetMachineRef(LLVMOpaqueTargetMachine* va
         {
             return (LLVMOpaqueTargetMachine*)value.Pointer;
         }
+
+        public string CreateTargetDataLayout()
+        {
+            var pDataLayout = LLVM.CreateTargetDataLayout(this);
+
+            if (pDataLayout is null)
+            {
+                return string.Empty;
+            }
+
+            var span = new ReadOnlySpan<byte>(pDataLayout, int.MaxValue);
+            return span.Slice(0, span.IndexOf((byte)'\0')).AsString();
+        }
+
+        public bool TryEmitToFile(LLVMModuleRef module, string fileName, LLVMCodeGenFileType codegen, out string message)
+        {
+            using (var marshaledFileName = new MarshaledString(fileName))
+            {
+                sbyte* errorMessage;
+
+                int result = LLVM.TargetMachineEmitToFile(this, module, marshaledFileName, codegen, &errorMessage);
+
+                if (errorMessage is null)
+                {
+                    message = string.Empty;
+                }
+                else
+                {
+                    var span = new ReadOnlySpan<byte>(errorMessage, int.MaxValue);
+                    message = span.Slice(0, span.IndexOf((byte)'\0')).AsString();
+                    LLVM.DisposeErrorMessage(errorMessage);
+                }
+
+                return result == 0;
+            }
+        }
+
+        public void EmitToFile(LLVMModuleRef module, string fileName, LLVMCodeGenFileType codegen)
+        {
+            if (!TryEmitToFile(module, fileName, codegen, out string Error))
+            {
+                throw new ExternalException(Error);
+            }
+        }
     }
 }