1 files changed, 95 insertions, 0 deletions
diff --git a/ARMeilleure/Translation/Dominance.cs b/ARMeilleure/Translation/Dominance.cs
new file mode 100644
index 00000000..bb55169e
--- /dev/null
+++ b/ARMeilleure/Translation/Dominance.cs
@@ -0,0 +1,95 @@
+using ARMeilleure.IntermediateRepresentation;
+using System.Diagnostics;
+
+namespace ARMeilleure.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(ControlFlowGraph cfg)
+        {
+            BasicBlock Intersect(BasicBlock block1, BasicBlock block2)
+            {
+                while (block1 != block2)
+                {
+                    while (cfg.PostOrderMap[block1.Index] < cfg.PostOrderMap[block2.Index])
+                    {
+                        block1 = block1.ImmediateDominator;
+                    }
+
+                    while (cfg.PostOrderMap[block2.Index] < cfg.PostOrderMap[block1.Index])
+                    {
+                        block2 = block2.ImmediateDominator;
+                    }
+                }
+
+                return block1;
+            }
+
+            cfg.Entry.ImmediateDominator = cfg.Entry;
+
+            Debug.Assert(cfg.Entry == cfg.PostOrderBlocks[cfg.PostOrderBlocks.Length - 1]);
+
+            bool modified;
+
+            do
+            {
+                modified = false;
+
+                for (int blkIndex = cfg.PostOrderBlocks.Length - 2; blkIndex >= 0; blkIndex--)
+                {
+                    BasicBlock block = cfg.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(ControlFlowGraph cfg)
+        {
+            foreach (BasicBlock block in cfg.Blocks)
+            {
+                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;
+                    }
+                }
+            }
+        }
+    }
+}
+\ No newline at end of file