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