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@ -18,6 +18,7 @@
@@ -18,6 +18,7 @@
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using System; |
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using System.Collections.Generic; |
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using System.Diagnostics; |
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using System.Linq; |
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using System.Text; |
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using ICSharpCode.Decompiler.Util; |
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@ -109,7 +110,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
@@ -109,7 +110,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
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/// </summary>
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bool MatchDoWhileLoop(BlockContainer loop) |
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{ |
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(List<IfInstruction> conditions, ILInstruction exit, bool swap, bool split) = AnalyzeDoWhileConditions(loop); |
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(List<IfInstruction> conditions, ILInstruction exit, bool swap, bool split, bool unwrap) = AnalyzeDoWhileConditions(loop); |
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// not a do-while loop, exit.
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if (conditions == null || conditions.Count == 0) |
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return false; |
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@ -117,6 +118,24 @@ namespace ICSharpCode.Decompiler.IL.Transforms
@@ -117,6 +118,24 @@ namespace ICSharpCode.Decompiler.IL.Transforms
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Block conditionBlock; |
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// first we remove all extracted instructions from the original block.
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var originalBlock = (Block)exit.Parent; |
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if (unwrap) { |
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// we found a condition block nested in a condition that is followed by a return statement:
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// we flip the condition and swap the blocks
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Debug.Assert(originalBlock.Parent is IfInstruction); |
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var returnCondition = (IfInstruction)originalBlock.Parent; |
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var topLevelBlock = (Block)returnCondition.Parent; |
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Debug.Assert(topLevelBlock.Parent == loop); |
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var leaveFunction = topLevelBlock.Instructions[returnCondition.ChildIndex + 1]; |
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Debug.Assert(leaveFunction.MatchReturn(out _)); |
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returnCondition.Condition = Comp.LogicNot(returnCondition.Condition); |
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returnCondition.TrueInst = leaveFunction; |
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// simplify the condition:
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new ExpressionTransforms().Run(topLevelBlock, returnCondition.ChildIndex, new StatementTransformContext(new BlockTransformContext(context))); |
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topLevelBlock.Instructions.RemoveAt(returnCondition.ChildIndex + 1); |
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topLevelBlock.Instructions.AddRange(originalBlock.Instructions); |
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originalBlock = topLevelBlock; |
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split = true; |
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} |
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originalBlock.Instructions.RemoveRange(originalBlock.Instructions.Count - conditions.Count - 1, conditions.Count + 1); |
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// we need to split the block:
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if (split) { |
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@ -161,22 +180,21 @@ namespace ICSharpCode.Decompiler.IL.Transforms
@@ -161,22 +180,21 @@ namespace ICSharpCode.Decompiler.IL.Transforms
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return true; |
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} |
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static (List<IfInstruction> conditions, ILInstruction exit, bool swap, bool split) AnalyzeDoWhileConditions(BlockContainer loop) |
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static (List<IfInstruction> conditions, ILInstruction exit, bool swap, bool split, bool unwrap) AnalyzeDoWhileConditions(BlockContainer loop) |
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{ |
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bool swap; |
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// we iterate over all blocks from the bottom, because the entry-point
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// should only be considered as condition block, if there are no other blocks.
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foreach (var block in loop.Blocks.Reverse()) { |
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// first we match the end of the block:
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if (MatchDoWhileConditionBlock(loop, block, out swap)) { |
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if (MatchDoWhileConditionBlock(loop, block, out bool swap, out bool unwrapCondtionBlock, out Block conditionBlock)) { |
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// now collect all instructions that are usable as loop conditions
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var conditions = CollectConditions(loop, block, swap); |
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var conditions = CollectConditions(loop, conditionBlock, swap); |
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// split only if the block is either the entry-point or contains other instructions as well.
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var split = block == loop.EntryPoint || block.Instructions.Count > conditions.Count + 1; // + 1 is the final leave/branch.
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return (conditions, block.Instructions.Last(), swap, split); |
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var split = conditionBlock == loop.EntryPoint || conditionBlock.Instructions.Count > conditions.Count + 1; // + 1 is the final leave/branch.
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return (conditions, conditionBlock.Instructions.Last(), swap, split, unwrapCondtionBlock); |
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} |
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} |
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return (null, null, false, false); |
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return (null, null, false, false, false); |
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} |
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/// <summary>
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@ -216,7 +234,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
@@ -216,7 +234,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
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return false; |
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} |
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static bool MatchDoWhileConditionBlock(BlockContainer loop, Block block, out bool swapBranches) |
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static bool MatchDoWhileConditionBlock(BlockContainer loop, Block block, out bool swapBranches, out bool unwrapCondtionBlock, out Block conditionBlock) |
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{ |
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// match the end of the block:
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// if (condition) branch entry-point else nop
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@ -225,6 +243,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
@@ -225,6 +243,8 @@ namespace ICSharpCode.Decompiler.IL.Transforms
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// if (condition) leave loop else nop
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// branch entry-point
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swapBranches = false; |
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unwrapCondtionBlock = false; |
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conditionBlock = block; |
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// empty block?
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if (block.Instructions.Count < 2) |
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return false; |
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@ -233,6 +253,18 @@ namespace ICSharpCode.Decompiler.IL.Transforms
@@ -233,6 +253,18 @@ namespace ICSharpCode.Decompiler.IL.Transforms
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// no IfInstruction or already transformed?
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if (ifInstruction == null || !ifInstruction.FalseInst.MatchNop()) |
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return false; |
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// the block ends in a return statement preceeded by an IfInstruction
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// take a look at the nested block and check if that might be a condition block
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if (last.MatchReturn(out _) && ifInstruction.TrueInst is Block nestedConditionBlock) { |
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if (nestedConditionBlock.Instructions.Count < 2) |
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return false; |
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last = nestedConditionBlock.Instructions.Last(); |
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ifInstruction = nestedConditionBlock.Instructions.SecondToLastOrDefault() as IfInstruction; |
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if (ifInstruction == null || !ifInstruction.FalseInst.MatchNop()) |
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return false; |
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unwrapCondtionBlock = true; |
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conditionBlock = nestedConditionBlock; |
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} |
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// if the last instruction is a branch
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// we assume the branch instructions need to be swapped.
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if (last.MatchBranch(loop.EntryPoint)) |
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Siegfried Pammer
8 years ago