Initial work

Ryujinx.Graphics.Shader/StructuredIr/GotoElimination.cs

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+using Ryujinx.Graphics.Shader.IntermediateRepresentation;
+using System;
+using System.Collections.Generic;
+
+using static Ryujinx.Graphics.Shader.StructuredIr.AstHelper;
+
+namespace Ryujinx.Graphics.Shader.StructuredIr
+{
+    static class GotoElimination
+    {
+        // This is a modified version of the algorithm presented on the paper
+        // "Taming Control Flow: A Structured Approach to Eliminating Goto Statements".
+        public static void Eliminate(GotoStatement[] gotos)
+        {
+            for (int index = gotos.Length - 1; index >= 0; index--)
+            {
+                GotoStatement stmt = gotos[index];
+
+                AstBlock gBlock = ParentBlock(stmt.Goto);
+                AstBlock lBlock = ParentBlock(stmt.Label);
+
+                int gLevel = Level(gBlock);
+                int lLevel = Level(lBlock);
+
+                if (IndirectlyRelated(gBlock, lBlock, gLevel, lLevel))
+                {
+                    AstBlock drBlock = gBlock;
+
+                    int drLevel = gLevel;
+
+                    do
+                    {
+                        drBlock = drBlock.Parent;
+
+                        drLevel--;
+                    }
+                    while (!DirectlyRelated(drBlock, lBlock, drLevel, lLevel));
+
+                    MoveOutward(stmt, gLevel, drLevel);
+
+                    gBlock = drBlock;
+                    gLevel = drLevel;
+
+                    if (Previous(stmt.Goto) is AstBlock elseBlock && elseBlock.Type == AstBlockType.Else)
+                    {
+                        // It's possible that the label was enclosed inside an else block,
+                        // in this case we need to update the block and level.
+                        // We also need to set the IsLoop for the case when the label is
+                        // now before the goto, due to the newly introduced else block.
+                        lBlock = ParentBlock(stmt.Label);
+
+                        lLevel = Level(lBlock);
+
+                        if (!IndirectlyRelated(elseBlock, lBlock, gLevel + 1, lLevel))
+                        {
+                            stmt.IsLoop = true;
+                        }
+                    }
+                }
+
+                if (DirectlyRelated(gBlock, lBlock, gLevel, lLevel))
+                {
+                    if (gLevel > lLevel)
+                    {
+                        MoveOutward(stmt, gLevel, lLevel);
+                    }
+                    else
+                    {
+                        if (stmt.IsLoop)
+                        {
+                            Lift(stmt);
+                        }
+
+                        MoveInward(stmt);
+                    }
+                }
+
+                gBlock = ParentBlock(stmt.Goto);
+
+                if (stmt.IsLoop)
+                {
+                    EncloseDoWhile(stmt, gBlock, stmt.Label);
+                }
+                else
+                {
+                    Enclose(gBlock, AstBlockType.If, stmt.Condition, Next(stmt.Goto), stmt.Label);
+                }
+
+                gBlock.Remove(stmt.Goto);
+            }
+        }
+
+        private static bool IndirectlyRelated(AstBlock lBlock, AstBlock rBlock, int lLevel, int rlevel)
+        {
+            return !(lBlock == rBlock || DirectlyRelated(lBlock, rBlock, lLevel, rlevel));
+        }
+
+        private static bool DirectlyRelated(AstBlock lBlock, AstBlock rBlock, int lLevel, int rLevel)
+        {
+            // If the levels are equal, they can be either siblings or indirectly related.
+            if (lLevel == rLevel)
+            {
+                return false;
+            }
+
+            IAstNode block;
+            IAstNode other;
+
+            int blockLvl, otherLvl;
+
+            if (lLevel > rLevel)
+            {
+                block    = lBlock;
+                blockLvl = lLevel;
+                other    = rBlock;
+                otherLvl = rLevel;
+            }
+            else /* if (rLevel > lLevel) */
+            {
+                block    = rBlock;
+                blockLvl = rLevel;
+                other    = lBlock;
+                otherLvl = lLevel;
+            }
+
+            while (blockLvl >= otherLvl)
+            {
+                if (block == other)
+                {
+                    return true;
+                }
+
+                block = block.Parent;
+
+                blockLvl--;
+            }
+
+            return false;
+        }
+
+        private static void Lift(GotoStatement stmt)
+        {
+            AstBlock block = ParentBlock(stmt.Goto);
+
+            AstBlock[] path = BackwardsPath(block, ParentBlock(stmt.Label));
+
+            AstBlock loopFirstStmt = path[path.Length - 1];
+
+            if (loopFirstStmt.Type == AstBlockType.Else)
+            {
+                loopFirstStmt = Previous(loopFirstStmt) as AstBlock;
+
+                if (loopFirstStmt == null || loopFirstStmt.Type != AstBlockType.If)
+                {
+                    throw new InvalidOperationException("Found an else without a matching if.");
+                }
+            }
+
+            AstBlock newBlock = EncloseDoWhile(stmt, block, loopFirstStmt);
+
+            block.Remove(stmt.Goto);
+
+            newBlock.AddFirst(stmt.Goto);
+
+            stmt.IsLoop = false;
+        }
+
+        private static void MoveOutward(GotoStatement stmt, int gLevel, int lLevel)
+        {
+            AstBlock origin = ParentBlock(stmt.Goto);
+
+            AstBlock block = origin;
+
+            // Check if a loop is enclosing the goto, and the block that is
+            // directly related to the label is above the loop block.
+            // In that case, we need to introduce a break to get out of the loop.
+            AstBlock loopBlock = origin;
+
+            int loopLevel = gLevel;
+
+            while (loopLevel > lLevel)
+            {
+                AstBlock child = loopBlock;
+
+                loopBlock = loopBlock.Parent;
+
+                loopLevel--;
+
+                if (child.Type == AstBlockType.DoWhile)
+                {
+                    EncloseSingleInst(stmt, Instruction.LoopBreak);
+
+                    block.Remove(stmt.Goto);
+
+                    loopBlock.AddAfter(child, stmt.Goto);
+
+                    block  = loopBlock;
+                    gLevel = loopLevel;
+                }
+            }
+
+            // Insert ifs to skip the parts that shouldn't be executed due to the goto.
+            bool tryInsertElse = stmt.IsUnconditional && origin.Type == AstBlockType.If;
+
+            while (gLevel > lLevel)
+            {
+                Enclose(block, AstBlockType.If, stmt.Condition, Next(stmt.Goto));
+
+                block.Remove(stmt.Goto);
+
+                AstBlock child = block;
+
+                // We can't move the goto in the middle of a if and a else block, in
+                // this case we need to move it after the else.
+                // IsLoop may need to be updated if the label is inside the else, as
+                // introducing a loop is the only way to ensure the else will be executed.
+                if (Next(child) is AstBlock elseBlock && elseBlock.Type == AstBlockType.Else)
+                {
+                    child = elseBlock;
+                }
+
+                block = block.Parent;
+
+                block.AddAfter(child, stmt.Goto);
+
+                gLevel--;
+
+                if (tryInsertElse && child == origin)
+                {
+                    AstBlock lBlock = ParentBlock(stmt.Label);
+
+                    IAstNode last = block == lBlock && !stmt.IsLoop ? stmt.Label : null;
+
+                    AstBlock newBlock = Enclose(block, AstBlockType.Else, null, Next(stmt.Goto), last);
+
+                    if (newBlock != null)
+                    {
+                        block.Remove(stmt.Goto);
+
+                        block.AddAfter(newBlock, stmt.Goto);
+                    }
+                }
+            }
+        }
+
+        private static void MoveInward(GotoStatement stmt)
+        {
+            AstBlock block = ParentBlock(stmt.Goto);
+
+            AstBlock[] path = BackwardsPath(block, ParentBlock(stmt.Label));
+
+            for (int index = path.Length - 1; index >= 0; index--)
+            {
+                AstBlock child = path[index];
+                AstBlock last  = child;
+
+                if (child.Type == AstBlockType.If)
+                {
+                    // Modify the if condition to allow it to be entered by the goto.
+                    if (!ContainsCondComb(child.Condition, Instruction.LogicalOr, stmt.Condition))
+                    {
+                        child.OrCondition(stmt.Condition);
+                    }
+                }
+                else if (child.Type == AstBlockType.Else)
+                {
+                    // Modify the matching if condition to force the else to be entered by the goto.
+                    if (!(Previous(child) is AstBlock ifBlock) || ifBlock.Type != AstBlockType.If)
+                    {
+                        throw new InvalidOperationException("Found an else without a matching if.");
+                    }
+
+                    IAstNode cond = InverseCond(stmt.Condition);
+
+                    if (!ContainsCondComb(ifBlock.Condition, Instruction.LogicalAnd, cond))
+                    {
+                        ifBlock.AndCondition(cond);
+                    }
+
+                    last = ifBlock;
+                }
+
+                Enclose(block, AstBlockType.If, stmt.Condition, Next(stmt.Goto), last);
+
+                block.Remove(stmt.Goto);
+
+                child.AddFirst(stmt.Goto);
+
+                block = child;
+            }
+        }
+
+        private static bool ContainsCondComb(IAstNode node, Instruction inst, IAstNode newCond)
+        {
+            while (node is AstOperation operation && operation.SourcesCount == 2)
+            {
+                if (operation.Inst == inst && IsSameCond(operation.GetSource(1), newCond))
+                {
+                    return true;
+                }
+
+                node = operation.GetSource(0);
+            }
+
+            return false;
+        }
+
+        private static AstBlock EncloseDoWhile(GotoStatement stmt, AstBlock block, IAstNode first)
+        {
+            if (block.Type == AstBlockType.DoWhile && first == block.First)
+            {
+                // We only need to insert the continue if we're not at the end of the loop,
+                // or if our condition is different from the loop condition.
+                if (Next(stmt.Goto) != null || block.Condition != stmt.Condition)
+                {
+                    EncloseSingleInst(stmt, Instruction.LoopContinue);
+                }
+
+                // Modify the do-while condition to allow it to continue.
+                if (!ContainsCondComb(block.Condition, Instruction.LogicalOr, stmt.Condition))
+                {
+                    block.OrCondition(stmt.Condition);
+                }
+
+                return block;
+            }
+
+            return Enclose(block, AstBlockType.DoWhile, stmt.Condition, first, stmt.Goto);
+        }
+
+        private static void EncloseSingleInst(GotoStatement stmt, Instruction inst)
+        {
+            AstBlock block = ParentBlock(stmt.Goto);
+
+            AstBlock newBlock = new AstBlock(AstBlockType.If, stmt.Condition);
+
+            block.AddAfter(stmt.Goto, newBlock);
+
+            newBlock.AddFirst(new AstOperation(inst));
+        }
+
+        private static AstBlock Enclose(
+            AstBlock     block,
+            AstBlockType type,
+            IAstNode     cond,
+            IAstNode     first,
+            IAstNode     last  = null)
+        {
+            if (first == last)
+            {
+                return null;
+            }
+
+            if (type == AstBlockType.If)
+            {
+                cond = InverseCond(cond);
+            }
+
+            // Do a quick check, if we are enclosing a single block,
+            // and the block type/condition matches the one we're going
+            // to create, then we don't need a new block, we can just
+            // return the old one.
+            bool hasSingleNode = Next(first) == last;
+
+            if (hasSingleNode && BlockMatches(first, type, cond))
+            {
+                return first as AstBlock;
+            }
+
+            AstBlock newBlock = new AstBlock(type, cond);
+
+            block.AddBefore(first, newBlock);
+
+            while (first != last)
+            {
+                IAstNode next = Next(first);
+
+                block.Remove(first);
+
+                newBlock.Add(first);
+
+                first = next;
+            }
+
+            return newBlock;
+        }
+
+        private static bool BlockMatches(IAstNode node, AstBlockType type, IAstNode cond)
+        {
+            if (!(node is AstBlock block))
+            {
+                return false;
+            }
+
+            return block.Type == type && IsSameCond(block.Condition, cond);
+        }
+
+        private static bool IsSameCond(IAstNode lCond, IAstNode rCond)
+        {
+            if (lCond is AstOperation lCondOp && lCondOp.Inst == Instruction.LogicalNot)
+            {
+                if (!(rCond is AstOperation rCondOp) || rCondOp.Inst != lCondOp.Inst)
+                {
+                    return false;
+                }
+
+                lCond = lCondOp.GetSource(0);
+                rCond = rCondOp.GetSource(0);
+            }
+
+            return lCond == rCond;
+        }
+
+        private static AstBlock ParentBlock(IAstNode node)
+        {
+            if (node is AstBlock block)
+            {
+                return block.Parent;
+            }
+
+            while (!(node is AstBlock))
+            {
+                node = node.Parent;
+            }
+
+            return node as AstBlock;
+        }
+
+        private static AstBlock[] BackwardsPath(AstBlock top, AstBlock bottom)
+        {
+            AstBlock block = bottom;
+
+            List<AstBlock> path = new List<AstBlock>();
+
+            while (block != top)
+            {
+                path.Add(block);
+
+                block = block.Parent;
+            }
+
+            return path.ToArray();
+        }
+
+        private static int Level(IAstNode node)
+        {
+            int level = 0;
+
+            while (node != null)
+            {
+                level++;
+
+                node = node.Parent;
+            }
+
+            return level;
+        }
+    }
+}