1 files changed, 305 insertions, 0 deletions
diff --git a/ARMeilleure/CodeGen/X86/CodeGenContext.cs b/ARMeilleure/CodeGen/X86/CodeGenContext.cs
new file mode 100644
index 00000000..d719b516
--- /dev/null
+++ b/ARMeilleure/CodeGen/X86/CodeGenContext.cs
@@ -0,0 +1,305 @@
+using ARMeilleure.CodeGen.RegisterAllocators;
+using ARMeilleure.Common;
+using ARMeilleure.IntermediateRepresentation;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+
+namespace ARMeilleure.CodeGen.X86
+{
+    class CodeGenContext
+    {
+        private const int ReservedBytesForJump = 1;
+
+        private Stream _stream;
+
+        public int StreamOffset => (int)_stream.Length;
+
+        public AllocationResult AllocResult { get; }
+
+        public Assembler Assembler { get; }
+
+        public BasicBlock CurrBlock { get; private set; }
+
+        public int CallArgsRegionSize { get; }
+        public int XmmSaveRegionSize  { get; }
+
+        private 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)
+            {
+                IsConditional = false;
+                Condition     = 0;
+                Target        = target;
+                JumpPosition  = jumpPosition;
+
+                RelativeOffset = 0;
+
+                InstSize = 0;
+            }
+
+            public Jump(X86Condition condition, BasicBlock target, long jumpPosition)
+            {
+                IsConditional = true;
+                Condition     = condition;
+                Target        = target;
+                JumpPosition  = jumpPosition;
+
+                RelativeOffset = 0;
+
+                InstSize = 0;
+            }
+        }
+
+        private List<Jump> _jumps;
+
+        private X86Condition _jNearCondition;
+
+        private long _jNearPosition;
+        private int  _jNearLength;
+
+        public CodeGenContext(Stream stream, AllocationResult allocResult, int maxCallArgs, int blocksCount)
+        {
+            _stream = stream;
+
+            AllocResult = allocResult;
+
+            Assembler = new Assembler(stream);
+
+            CallArgsRegionSize = GetCallArgsRegionSize(allocResult, maxCallArgs, out int xmmSaveRegionSize);
+            XmmSaveRegionSize  = xmmSaveRegionSize;
+
+            _blockOffsets = new long[blocksCount];
+
+            _jumps = new List<Jump>();
+        }
+
+        private 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).
+            int intMask = CallingConvention.GetIntCalleeSavedRegisters() & allocResult.IntUsedRegisters;
+            int vecMask = CallingConvention.GetVecCalleeSavedRegisters() & allocResult.VecUsedRegisters;
+
+            xmmSaveRegionSize = BitUtils.CountBits(vecMask) * 16;
+
+            int calleeSaveRegionSize = BitUtils.CountBits(intMask) * 8 + xmmSaveRegionSize + 8;
+
+            int argsCount = maxCallArgs;
+
+            if (argsCount < 0)
+            {
+                // When the function has no calls, argsCount is -1.
+                // In this case, we don't need to allocate the shadow space.
+                argsCount = 0;
+            }
+            else if (argsCount < 4)
+            {
+                // The ABI mandates that the space for at least 4 arguments
+                // is reserved on the stack (this is called shadow space).
+                argsCount = 4;
+            }
+
+            int frameSize = calleeSaveRegionSize + allocResult.SpillRegionSize;
+
+            // TODO: Instead of always multiplying by 16 (the largest possible size of a variable,
+            // since a V128 has 16 bytes), we should calculate the exact size consumed by the
+            // arguments passed to the called functions on the stack.
+            int callArgsAndFrameSize = frameSize + argsCount * 16;
+
+            // Ensure that the Stack Pointer will be aligned to 16 bytes.
+            callArgsAndFrameSize = (callArgsAndFrameSize + 0xf) & ~0xf;
+
+            return callArgsAndFrameSize - frameSize;
+        }
+
+        public void EnterBlock(BasicBlock block)
+        {
+            _blockOffsets[block.Index] = _stream.Position;
+
+            CurrBlock = block;
+        }
+
+        public void JumpTo(BasicBlock target)
+        {
+            _jumps.Add(new Jump(target, _stream.Position));
+
+            WritePadding(ReservedBytesForJump);
+        }
+
+        public void JumpTo(X86Condition condition, BasicBlock target)
+        {
+            _jumps.Add(new Jump(condition, target, _stream.Position));
+
+            WritePadding(ReservedBytesForJump);
+        }
+
+        public void JumpToNear(X86Condition condition)
+        {
+            _jNearCondition = condition;
+            _jNearPosition  = _stream.Position;
+            _jNearLength    = Assembler.GetJccLength(0);
+
+            _stream.Seek(_jNearLength, SeekOrigin.Current);
+        }
+
+        public void JumpHere()
+        {
+            long currentPosition = _stream.Position;
+
+            _stream.Seek(_jNearPosition, SeekOrigin.Begin);
+
+            long offset = currentPosition - (_jNearPosition + _jNearLength);
+
+            Debug.Assert(_jNearLength == Assembler.GetJccLength(offset), "Relative offset doesn't fit on near jump.");
+
+            Assembler.Jcc(_jNearCondition, offset);
+
+            _stream.Seek(currentPosition, SeekOrigin.Begin);
+        }
+
+        private void WritePadding(int size)
+        {
+            while (size-- > 0)
+            {
+                _stream.WriteByte(0);
+            }
+        }
+
+        public byte[] GetCode()
+        {
+            // Write jump relative offsets.
+            bool modified;
+
+            do
+            {
+                modified = false;
+
+                for (int index = 0; index < _jumps.Count; index++)
+                {
+                    Jump jump = _jumps[index];
+
+                    long jumpTarget = _blockOffsets[jump.Target.Index];
+
+                    long offset = jumpTarget - jump.JumpPosition;
+
+                    if (offset < 0)
+                    {
+                        for (int index2 = index - 1; index2 >= 0; index2--)
+                        {
+                            Jump jump2 = _jumps[index2];
+
+                            if (jump2.JumpPosition < jumpTarget)
+                            {
+                                break;
+                            }
+
+                            offset -= jump2.InstSize - ReservedBytesForJump;
+                        }
+                    }
+                    else
+                    {
+                        for (int index2 = index + 1; index2 < _jumps.Count; index2++)
+                        {
+                            Jump jump2 = _jumps[index2];
+
+                            if (jump2.JumpPosition >= jumpTarget)
+                            {
+                                break;
+                            }
+
+                            offset += jump2.InstSize - ReservedBytesForJump;
+                        }
+
+                        offset -= ReservedBytesForJump;
+                    }
+
+                    if (jump.IsConditional)
+                    {
+                        jump.InstSize = Assembler.GetJccLength(offset);
+                    }
+                    else
+                    {
+                        jump.InstSize = Assembler.GetJmpLength(offset);
+                    }
+
+                    // The jump is relative to the next instruction, not the current one.
+                    // Since we didn't know the next instruction address when calculating
+                    // the offset (as the size of the current jump instruction was not know),
+                    // we now need to compensate the offset with the jump instruction size.
+                    // It's also worth to note that:
+                    // - This is only needed for backward jumps.
+                    // - The GetJmpLength and GetJccLength also compensates the offset
+                    // internally when computing the jump instruction size.
+                    if (offset < 0)
+                    {
+                        offset -= jump.InstSize;
+                    }
+
+                    if (jump.RelativeOffset != offset)
+                    {
+                        modified = true;
+                    }
+
+                    jump.RelativeOffset = offset;
+
+                    _jumps[index] = jump;
+                }
+            }
+            while (modified);
+
+            // Write the code, ignoring the dummy bytes after jumps, into a new stream.
+            _stream.Seek(0, SeekOrigin.Begin);
+
+            using (MemoryStream codeStream = new MemoryStream())
+            {
+                Assembler assembler = new Assembler(codeStream);
+
+                byte[] buffer;
+
+                for (int index = 0; index < _jumps.Count; index++)
+                {
+                    Jump jump = _jumps[index];
+
+                    buffer = new byte[jump.JumpPosition - _stream.Position];
+
+                    _stream.Read(buffer, 0, buffer.Length);
+                    _stream.Seek(ReservedBytesForJump, SeekOrigin.Current);
+
+                    codeStream.Write(buffer);
+
+                    if (jump.IsConditional)
+                    {
+                        assembler.Jcc(jump.Condition, jump.RelativeOffset);
+                    }
+                    else
+                    {
+                        assembler.Jmp(jump.RelativeOffset);
+                    }
+                }
+
+                buffer = new byte[_stream.Length - _stream.Position];
+
+                _stream.Read(buffer, 0, buffer.Length);
+
+                codeStream.Write(buffer);
+
+                return codeStream.ToArray();
+            }
+        }
+    }
+}
+\ No newline at end of file