1 files changed, 75 insertions, 0 deletions
diff --git a/ARMeilleure/Decoders/Optimizations/TailCallRemover.cs b/ARMeilleure/Decoders/Optimizations/TailCallRemover.cs
new file mode 100644
index 00000000..2d6439ba
--- /dev/null
+++ b/ARMeilleure/Decoders/Optimizations/TailCallRemover.cs
@@ -0,0 +1,75 @@
+using ARMeilleure.Decoders;
+using System;
+using System.Collections.Generic;
+
+namespace ARMeilleure.Decoders.Optimizations
+{
+    static class TailCallRemover
+    {
+        public static void RunPass(ulong entryAddress, List<Block> blocks)
+        {
+            // Detect tail calls:
+            // - Assume this function spans the space covered by contiguous code blocks surrounding the entry address.
+            // - Unconditional jump to an area outside this contiguous region will be treated as a tail call.
+            // - Include a small allowance for jumps outside the contiguous range.
+
+            if (!Decoder.BinarySearch(blocks, entryAddress, out int entryBlockId))
+            {
+                throw new InvalidOperationException("Function entry point is not contained in a block.");
+            }
+
+            const ulong allowance = 4;
+            Block entryBlock = blocks[entryBlockId];
+            int startBlockIndex = entryBlockId;
+            Block startBlock = entryBlock;
+            int endBlockIndex = entryBlockId;
+            Block endBlock = entryBlock;
+
+            for (int i = entryBlockId + 1; i < blocks.Count; i++) // Search forwards.
+            {
+                Block block = blocks[i];
+                if (endBlock.EndAddress < block.Address - allowance)
+                {
+                    break; // End of contiguous function.
+                }
+
+                endBlock = block;
+                endBlockIndex = i;
+            }
+
+            for (int i = entryBlockId - 1; i >= 0; i--) // Search backwards.
+            {
+                Block block = blocks[i];
+                if (startBlock.Address > block.EndAddress + allowance)
+                {
+                    break; // End of contiguous function.
+                }
+
+                startBlock = block;
+                startBlockIndex = i;
+            }
+
+            if (startBlockIndex == 0 && endBlockIndex == blocks.Count - 1)
+            {
+                return; // Nothing to do here.
+            }
+
+            // Replace all branches to blocks outside the range with null, and force a tail call.
+
+            for (int i = startBlockIndex; i <= endBlockIndex; i++)
+            {
+                Block block = blocks[i];
+                if (block.Branch != null && (block.Branch.Address > endBlock.EndAddress || block.Branch.EndAddress < startBlock.Address))
+                {
+                    block.Branch = null;
+                    block.TailCall = true;
+                }
+            }
+
+            // Finally, delete all blocks outside the contiguous range.
+
+            blocks.RemoveRange(endBlockIndex + 1, (blocks.Count - endBlockIndex) - 1);
+            blocks.RemoveRange(0, startBlockIndex);
+        }
+    }
+}