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.

3 files changed, 73 insertions, 89 deletions

diff --git a/ARMeilleure/CodeGen/X86/Assembler.cs b/ARMeilleure/CodeGen/X86/Assembler.cs
index 044f6047..95608756 100644
--- a/ARMeilleure/CodeGen/X86/Assembler.cs
+++ b/ARMeilleure/CodeGen/X86/Assembler.cs
@@ -1,6 +1,7 @@
+using ARMeilleure.CodeGen.Linking;
 using ARMeilleure.IntermediateRepresentation;
-using ARMeilleure.Translation.PTC;
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 
@@ -61,12 +62,12 @@ namespace ARMeilleure.CodeGen.X86
             }
         }
 
-        private static InstructionInfo[] _instTable;
+        private readonly static InstructionInfo[] _instTable;
 
-        private Stream _stream;
+        private readonly Stream _stream;
 
-        private PtcInfo _ptcInfo;
-        private bool    _ptcDisabled;
+        public List<RelocEntry> Relocs { get; }
+        public bool HasRelocs => Relocs != null;
 
         static Assembler()
         {
@@ -294,12 +295,10 @@ namespace ARMeilleure.CodeGen.X86
             _instTable[(int)inst] = info;
         }
 
-        public Assembler(Stream stream, PtcInfo ptcInfo = null)
+        public Assembler(Stream stream, bool relocatable)
         {
             _stream = stream;
-
-            _ptcInfo     = ptcInfo;
-            _ptcDisabled = ptcInfo == null;
+            Relocs = relocatable ? new List<RelocEntry>() : null;
         }
 
         public void Add(Operand dest, Operand source, OperandType type)
@@ -498,7 +497,7 @@ namespace ARMeilleure.CodeGen.X86
 
         public void Jcc(X86Condition condition, long offset)
         {
-            if (_ptcDisabled && ConstFitsOnS8(offset))
+            if (!HasRelocs && ConstFitsOnS8(offset))
             {
                 WriteByte((byte)(0x70 | (int)condition));
 
@@ -519,7 +518,7 @@ namespace ARMeilleure.CodeGen.X86
 
         public void Jmp(long offset)
         {
-            if (_ptcDisabled && ConstFitsOnS8(offset))
+            if (!HasRelocs && ConstFitsOnS8(offset))
             {
                 WriteByte(0xeb);
 
@@ -980,9 +979,9 @@ namespace ARMeilleure.CodeGen.X86
 
                         WriteByte((byte)(info.OpRImm64 + (dest.GetRegister().Index & 0b111)));
 
-                        if (_ptcInfo != default && source.Relocatable)
+                        if (HasRelocs && source.Relocatable)
                         {
-                            _ptcInfo.WriteRelocEntry(new RelocEntry((int)_stream.Position, source.Symbol));
+                            Relocs.Add(new RelocEntry((int)_stream.Position, source.Symbol));
                         }
 
                         WriteUInt64(imm);
@@ -1396,9 +1395,9 @@ namespace ARMeilleure.CodeGen.X86
             return ConstFitsOnS32(value);
         }
 
-        public static int GetJccLength(long offset, bool ptcDisabled = true)
+        public static int GetJccLength(long offset, bool relocatable = false)
         {
-            if (ptcDisabled && ConstFitsOnS8(offset < 0 ? offset - 2 : offset))
+            if (!relocatable && ConstFitsOnS8(offset < 0 ? offset - 2 : offset))
             {
                 return 2;
             }
@@ -1412,9 +1411,9 @@ namespace ARMeilleure.CodeGen.X86
             }
         }
 
-        public static int GetJmpLength(long offset, bool ptcDisabled = true)
+        public static int GetJmpLength(long offset, bool relocatable = false)
         {
-            if (ptcDisabled && ConstFitsOnS8(offset < 0 ? offset - 2 : offset))
+            if (!relocatable && ConstFitsOnS8(offset < 0 ? offset - 2 : offset))
             {
                 return 2;
             }
diff --git a/ARMeilleure/CodeGen/X86/CodeGenContext.cs b/ARMeilleure/CodeGen/X86/CodeGenContext.cs
index fa726f2f..7e96dd85 100644
--- a/ARMeilleure/CodeGen/X86/CodeGenContext.cs
+++ b/ARMeilleure/CodeGen/X86/CodeGenContext.cs
@@ -1,7 +1,7 @@
+using ARMeilleure.CodeGen.Linking;
 using ARMeilleure.CodeGen.RegisterAllocators;
 using ARMeilleure.Common;
 using ARMeilleure.IntermediateRepresentation;
-using ARMeilleure.Translation.PTC;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -13,10 +13,8 @@ namespace ARMeilleure.CodeGen.X86
     {
         private const int ReservedBytesForJump = 1;
 
-        private Stream _stream;
-
-        private PtcInfo _ptcInfo;
-        private bool    _ptcDisabled;
+        private readonly Stream _stream;
+        private readonly bool _relocatable;
 
         public int StreamOffset => (int)_stream.Length;
 
@@ -27,22 +25,17 @@ namespace ARMeilleure.CodeGen.X86
         public BasicBlock CurrBlock { get; private set; }
 
         public int CallArgsRegionSize { get; }
-        public int XmmSaveRegionSize  { get; }
+        public int XmmSaveRegionSize { get; }
 
-        private long[] _blockOffsets;
+        private readonly long[] _blockOffsets;
 
         private struct Jump
         {
             public bool IsConditional { get; }
-
             public X86Condition Condition { get; }
-
             public BasicBlock Target { get; }
-
             public long JumpPosition { get; }
-
             public long RelativeOffset { get; set; }
-
             public int InstSize { get; set; }
 
             public Jump(BasicBlock target, long jumpPosition, int instSize = 0)
@@ -70,33 +63,26 @@ namespace ARMeilleure.CodeGen.X86
             }
         }
 
-        private List<Jump> _jumps;
+        private readonly List<Jump> _jumps;
 
         private X86Condition _jNearCondition;
-
         private long _jNearPosition;
-        private int  _jNearLength;
+        private int _jNearLength;
 
-        public CodeGenContext(Stream stream, AllocationResult allocResult, int maxCallArgs, int blocksCount, PtcInfo ptcInfo = null)
+        public CodeGenContext(Stream stream, AllocationResult allocResult, int maxCallArgs, int blocksCount, bool relocatable)
         {
             _stream = stream;
+            _relocatable = relocatable;
+            _blockOffsets = new long[blocksCount];
+            _jumps = new List<Jump>();
 
             AllocResult = allocResult;
-
-            Assembler = new Assembler(stream, ptcInfo);
-
+            Assembler = new Assembler(stream, relocatable);
             CallArgsRegionSize = GetCallArgsRegionSize(allocResult, maxCallArgs, out int xmmSaveRegionSize);
             XmmSaveRegionSize  = xmmSaveRegionSize;
-
-            _blockOffsets = new long[blocksCount];
-
-            _jumps = new List<Jump>();
-
-            _ptcInfo     = ptcInfo;
-            _ptcDisabled = ptcInfo == null;
         }
 
-        private int GetCallArgsRegionSize(AllocationResult allocResult, int maxCallArgs, out int xmmSaveRegionSize)
+        private static int GetCallArgsRegionSize(AllocationResult allocResult, int maxCallArgs, out int xmmSaveRegionSize)
         {
             // We need to add 8 bytes to the total size, as the call to this
             // function already pushed 8 bytes (the return address).
@@ -144,7 +130,7 @@ namespace ARMeilleure.CodeGen.X86
 
         public void JumpTo(BasicBlock target)
         {
-            if (_ptcDisabled)
+            if (!_relocatable)
             {
                 _jumps.Add(new Jump(target, _stream.Position));
 
@@ -160,7 +146,7 @@ namespace ARMeilleure.CodeGen.X86
 
         public void JumpTo(X86Condition condition, BasicBlock target)
         {
-            if (_ptcDisabled)
+            if (!_relocatable)
             {
                 _jumps.Add(new Jump(condition, target, _stream.Position));
 
@@ -178,7 +164,7 @@ namespace ARMeilleure.CodeGen.X86
         {
             _jNearCondition = condition;
             _jNearPosition  = _stream.Position;
-            _jNearLength    = Assembler.GetJccLength(0, _ptcDisabled);
+            _jNearLength    = Assembler.GetJccLength(0, _relocatable);
 
             _stream.Seek(_jNearLength, SeekOrigin.Current);
         }
@@ -191,7 +177,7 @@ namespace ARMeilleure.CodeGen.X86
 
             long offset = currentPosition - (_jNearPosition + _jNearLength);
 
-            Debug.Assert(_jNearLength == Assembler.GetJccLength(offset, _ptcDisabled), "Relative offset doesn't fit on near jump.");
+            Debug.Assert(_jNearLength == Assembler.GetJccLength(offset, _relocatable), "Relative offset doesn't fit on near jump.");
 
             Assembler.Jcc(_jNearCondition, offset);
 
@@ -206,7 +192,7 @@ namespace ARMeilleure.CodeGen.X86
             }
         }
 
-        public byte[] GetCode()
+        public (byte[], RelocInfo) GetCode()
         {
             // Write jump relative offsets.
             bool modified;
@@ -223,7 +209,7 @@ namespace ARMeilleure.CodeGen.X86
 
                     long offset = jumpTarget - jump.JumpPosition;
 
-                    if (_ptcDisabled)
+                    if (!_relocatable)
                     {
                         if (offset < 0)
                         {
@@ -300,7 +286,7 @@ namespace ARMeilleure.CodeGen.X86
 
             using (MemoryStream codeStream = new MemoryStream())
             {
-                Assembler assembler = new Assembler(codeStream, _ptcInfo);
+                Assembler assembler = new Assembler(codeStream, _relocatable);
 
                 for (int index = 0; index < _jumps.Count; index++)
                 {
@@ -309,7 +295,7 @@ namespace ARMeilleure.CodeGen.X86
                     Span<byte> buffer = new byte[jump.JumpPosition - _stream.Position];
 
                     _stream.Read(buffer);
-                    _stream.Seek(_ptcDisabled ? ReservedBytesForJump : jump.InstSize, SeekOrigin.Current);
+                    _stream.Seek(!_relocatable ? ReservedBytesForJump : jump.InstSize, SeekOrigin.Current);
 
                     codeStream.Write(buffer);
 
@@ -325,7 +311,12 @@ namespace ARMeilleure.CodeGen.X86
 
                 _stream.CopyTo(codeStream);
 
-                return codeStream.ToArray();
+                var code = codeStream.ToArray();
+                var relocInfo = Assembler.HasRelocs
+                    ? new RelocInfo(Assembler.Relocs.ToArray())
+                    : RelocInfo.Empty;
+
+                return (code, relocInfo);
             }
         }
     }
diff --git a/ARMeilleure/CodeGen/X86/CodeGenerator.cs b/ARMeilleure/CodeGen/X86/CodeGenerator.cs
index 5818eb2e..924c113c 100644
--- a/ARMeilleure/CodeGen/X86/CodeGenerator.cs
+++ b/ARMeilleure/CodeGen/X86/CodeGenerator.cs
@@ -1,3 +1,4 @@
+using ARMeilleure.CodeGen.Linking;
 using ARMeilleure.CodeGen.Optimizations;
 using ARMeilleure.CodeGen.RegisterAllocators;
 using ARMeilleure.CodeGen.Unwinding;
@@ -5,7 +6,6 @@ using ARMeilleure.Common;
 using ARMeilleure.Diagnostics;
 using ARMeilleure.IntermediateRepresentation;
 using ARMeilleure.Translation;
-using ARMeilleure.Translation.PTC;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -91,7 +91,7 @@ namespace ARMeilleure.CodeGen.X86
             _instTable[(int)inst] = func;
         }
 
-        public static CompiledFunction Generate(CompilerContext cctx, PtcInfo ptcInfo = null)
+        public static CompiledFunction Generate(CompilerContext cctx)
         {
             ControlFlowGraph cfg = cctx.Cfg;
 
@@ -149,53 +149,47 @@ namespace ARMeilleure.CodeGen.X86
 
             Logger.StartPass(PassName.CodeGeneration);
 
-            using (MemoryStream stream = new MemoryStream())
-            {
-                CodeGenContext context = new CodeGenContext(stream, allocResult, maxCallArgs, cfg.Blocks.Count, ptcInfo);
+            bool relocatable = (cctx.Options & CompilerOptions.Relocatable) != 0;
+
+            using MemoryStream stream = new();
+
+            CodeGenContext context = new(stream, allocResult, maxCallArgs, cfg.Blocks.Count, relocatable);
 
-                UnwindInfo unwindInfo = WritePrologue(context);
+            UnwindInfo unwindInfo = WritePrologue(context);
 
-                ptcInfo?.WriteUnwindInfo(unwindInfo);
+            for (BasicBlock block = cfg.Blocks.First; block != null; block = block.ListNext)
+            {
+                context.EnterBlock(block);
 
-                for (BasicBlock block = cfg.Blocks.First; block != null; block = block.ListNext)
+                for (Operation node = block.Operations.First; node != default; node = node.ListNext)
                 {
-                    context.EnterBlock(block);
+                    GenerateOperation(context, node);
+                }
 
-                    for (Operation node = block.Operations.First; node != default; node = node.ListNext)
-                    {
-                        GenerateOperation(context, node);
-                    }
+                if (block.SuccessorsCount == 0)
+                {
+                    // The only blocks which can have 0 successors are exit blocks.
+                    Operation last = block.Operations.Last;
 
-                    if (block.SuccessorsCount == 0)
-                    {
-                        // The only blocks which can have 0 successors are exit blocks.
-                        Operation last = block.Operations.Last;
+                    Debug.Assert(last.Instruction == Instruction.Tailcall ||
+                                 last.Instruction == Instruction.Return);
+                }
+                else
+                {
+                    BasicBlock succ = block.GetSuccessor(0);
 
-                        Debug.Assert(last.Instruction == Instruction.Tailcall ||
-                                     last.Instruction == Instruction.Return);
-                    }
-                    else
+                    if (succ != block.ListNext)
                     {
-                        BasicBlock succ = block.GetSuccessor(0);
-
-                        if (succ != block.ListNext)
-                        {
-                            context.JumpTo(succ);
-                        }
+                        context.JumpTo(succ);
                     }
                 }
+            }
 
-                byte[] code = context.GetCode();
+            (byte[] code, RelocInfo relocInfo) = context.GetCode();
 
-                if (ptcInfo != null)
-                {
-                    ptcInfo.Code = code;
-                }
+            Logger.EndPass(PassName.CodeGeneration);
 
-                Logger.EndPass(PassName.CodeGeneration);
-
-                return new CompiledFunction(code, unwindInfo);
-            }
+            return new CompiledFunction(code, unwindInfo, relocInfo);
         }
 
         private static void GenerateOperation(CodeGenContext context, Operation operation)