Refactor PtcInfo (#2625)

* Refactor `PtcInfo`

This change reduces the coupling of `PtcInfo` by moving relocation
tracking to the backend. `RelocEntry`s remains as `RelocEntry`s through
out the pipeline until it actually needs to be written to the PTC
streams. Keeping this representation makes inspecting and manipulating
relocations after compilations less painful. This is something I needed
to do to patch relocations to 0 to diff dumps.

Contributes to #1125.

* Turn `Symbol` & `RelocInfo` into readonly structs

* Add documentation to `CompiledFunction`

* Remove `Compiler.Compile<T>`

Remove `Compiler.Compile<T>` and replace it by `Map<T>` of the
`CompiledFunction` returned.

ARMeilleure/CodeGen/CompiledFunction.cs

@@ -1,17 +1,56 @@
+using ARMeilleure.CodeGen.Linking;
 using ARMeilleure.CodeGen.Unwinding;
+using ARMeilleure.Translation.Cache;
+using System;
+using System.Runtime.InteropServices;
 
 namespace ARMeilleure.CodeGen
 {
-    struct CompiledFunction
+    /// <summary>
+    /// Represents a compiled function.
+    /// </summary>
+    readonly struct CompiledFunction
     {
+        /// <summary>
+        /// Gets the machine code of the <see cref="CompiledFunction"/>.
+        /// </summary>
         public byte[] Code { get; }
 
+        /// <summary>
+        /// Gets the <see cref="Unwinding.UnwindInfo"/> of the <see cref="CompiledFunction"/>.
+        /// </summary>
         public UnwindInfo UnwindInfo { get; }
 
-        public CompiledFunction(byte[] code, UnwindInfo unwindInfo)
+        /// <summary>
+        /// Gets the <see cref="Linking.RelocInfo"/> of the <see cref="CompiledFunction"/>.
+        /// </summary>
+        public RelocInfo RelocInfo { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CompiledFunction"/> struct with the specified machine code,
+        /// unwind info and relocation info.
+        /// </summary>
+        /// <param name="code">Machine code</param>
+        /// <param name="unwindInfo">Unwind info</param>
+        /// <param name="relocInfo">Relocation info</param>
+        internal CompiledFunction(byte[] code, UnwindInfo unwindInfo, RelocInfo relocInfo)
         {
             Code       = code;
             UnwindInfo = unwindInfo;
+            RelocInfo  = relocInfo;
+        }
+
+        /// <summary>
+        /// Maps the <see cref="CompiledFunction"/> onto the <see cref="JitCache"/> and returns a delegate of type
+        /// <typeparamref name="T"/> pointing to the mapped function.
+        /// </summary>
+        /// <typeparam name="T">Type of delegate</typeparam>
+        /// <returns>A delegate of type <typeparamref name="T"/> pointing to the mapped function</returns>
+        public T Map<T>()
+        {
+            IntPtr codePtr = JitCache.Map(this);
+
+            return Marshal.GetDelegateForFunctionPointer<T>(codePtr);
         }
     }
 }