1 files changed, 67 insertions, 0 deletions
diff --git a/Ryujinx.Graphics.Shader/Translation/Optimizations/Utils.cs b/Ryujinx.Graphics.Shader/Translation/Optimizations/Utils.cs
new file mode 100644
index 00000000..83ff8c40
--- /dev/null
+++ b/Ryujinx.Graphics.Shader/Translation/Optimizations/Utils.cs
@@ -0,0 +1,67 @@
+using Ryujinx.Graphics.Shader.IntermediateRepresentation;
+
+namespace Ryujinx.Graphics.Shader.Translation.Optimizations
+{
+    static class Utils
+    {
+        private static Operation FindBranchSource(BasicBlock block)
+        {
+            foreach (BasicBlock sourceBlock in block.Predecessors)
+            {
+                if (sourceBlock.Operations.Count > 0)
+                {
+                    Operation lastOp = sourceBlock.Operations.Last.Value as Operation;
+
+                    if (lastOp != null &&
+                        ((sourceBlock.Next == block && lastOp.Inst == Instruction.BranchIfFalse) ||
+                        (sourceBlock.Branch == block && lastOp.Inst == Instruction.BranchIfTrue)))
+                    {
+                        return lastOp;
+                    }
+                }
+            }
+
+            return null;
+        }
+
+        private static bool BlockConditionsMatch(BasicBlock currentBlock, BasicBlock queryBlock)
+        {
+            // Check if all the conditions for the query block are satisfied by the current block.
+            // Just checks the top-most conditional for now.
+
+            Operation currentBranch = FindBranchSource(currentBlock);
+            Operation queryBranch = FindBranchSource(queryBlock);
+
+            Operand currentCondition = currentBranch?.GetSource(0);
+            Operand queryCondition = queryBranch?.GetSource(0);
+
+            // The condition should be the same operand instance.
+
+            return currentBranch != null && queryBranch != null &&
+                   currentBranch.Inst == queryBranch.Inst &&
+                   currentCondition == queryCondition;
+        }
+
+        public static Operand FindLastOperation(Operand source, BasicBlock block)
+        {
+            if (source.AsgOp is PhiNode phiNode)
+            {
+                // This source can have a different value depending on a previous branch.
+                // Ensure that conditions met for that branch are also met for the current one.
+                // Prefer the latest sources for the phi node.
+
+                for (int i = phiNode.SourcesCount - 1; i >= 0; i--)
+                {
+                    BasicBlock phiBlock = phiNode.GetBlock(i);
+
+                    if (BlockConditionsMatch(block, phiBlock))
+                    {
+                        return phiNode.GetSource(i);
+                    }
+                }
+            }
+
+            return source;
+        }
+    }
+}