Initial work

Ryujinx.Graphics.Shader/Translation/Dominance.cs

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+using Ryujinx.Graphics.Shader.IntermediateRepresentation;
+using System.Collections.Generic;
+
+namespace Ryujinx.Graphics.Shader.Translation
+{
+    static class Dominance
+    {
+        // Those methods are an implementation of the algorithms on "A Simple, Fast Dominance Algorithm".
+        // https://www.cs.rice.edu/~keith/EMBED/dom.pdf
+        public static void FindDominators(BasicBlock entry, int blocksCount)
+        {
+            HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
+
+            Stack<BasicBlock> blockStack = new Stack<BasicBlock>();
+
+            List<BasicBlock> postOrderBlocks = new List<BasicBlock>(blocksCount);
+
+            int[] postOrderMap = new int[blocksCount];
+
+            visited.Add(entry);
+
+            blockStack.Push(entry);
+
+            while (blockStack.TryPop(out BasicBlock block))
+            {
+                if (block.Next != null && visited.Add(block.Next))
+                {
+                    blockStack.Push(block);
+                    blockStack.Push(block.Next);
+                }
+                else if (block.Branch != null && visited.Add(block.Branch))
+                {
+                    blockStack.Push(block);
+                    blockStack.Push(block.Branch);
+                }
+                else
+                {
+                    postOrderMap[block.Index] = postOrderBlocks.Count;
+
+                    postOrderBlocks.Add(block);
+                }
+            }
+
+            BasicBlock Intersect(BasicBlock block1, BasicBlock block2)
+            {
+                while (block1 != block2)
+                {
+                    while (postOrderMap[block1.Index] < postOrderMap[block2.Index])
+                    {
+                        block1 = block1.ImmediateDominator;
+                    }
+
+                    while (postOrderMap[block2.Index] < postOrderMap[block1.Index])
+                    {
+                        block2 = block2.ImmediateDominator;
+                    }
+                }
+
+                return block1;
+            }
+
+            entry.ImmediateDominator = entry;
+
+            bool modified;
+
+            do
+            {
+                modified = false;
+
+                for (int blkIndex = postOrderBlocks.Count - 2; blkIndex >= 0; blkIndex--)
+                {
+                    BasicBlock block = postOrderBlocks[blkIndex];
+
+                    BasicBlock newIDom = null;
+
+                    foreach (BasicBlock predecessor in block.Predecessors)
+                    {
+                        if (predecessor.ImmediateDominator != null)
+                        {
+                            if (newIDom != null)
+                            {
+                                newIDom = Intersect(predecessor, newIDom);
+                            }
+                            else
+                            {
+                                newIDom = predecessor;
+                            }
+                        }
+                    }
+
+                    if (block.ImmediateDominator != newIDom)
+                    {
+                        block.ImmediateDominator = newIDom;
+
+                        modified = true;
+                    }
+                }
+            }
+            while (modified);
+        }
+
+        public static void FindDominanceFrontiers(BasicBlock[] blocks)
+        {
+            for (int blkIndex = 0; blkIndex < blocks.Length; blkIndex++)
+            {
+                BasicBlock block = blocks[blkIndex];
+
+                if (block.Predecessors.Count < 2)
+                {
+                    continue;
+                }
+
+                for (int pBlkIndex = 0; pBlkIndex < block.Predecessors.Count; pBlkIndex++)
+                {
+                    BasicBlock current = block.Predecessors[pBlkIndex];
+
+                    while (current != block.ImmediateDominator)
+                    {
+                        current.DominanceFrontiers.Add(block);
+
+                        current = current.ImmediateDominator;
+                    }
+                }
+            }
+        }
+    }
+}