Improve the SSA Exit Stage (#1145)

* - Additional shift/division optimizations * - Additional optimizations * - Additional optimizations * - WIP * - WIP * - WIP * - WIP * - Implement #1142 (Phi improvement) * - Implement #1142 (Phi improvement) * - WIP
mosa · Sep 16, 2023 · 7c9945c · 7c9945c
1 parent 2f7f8d7
commit 7c9945c
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Showing 4 changed files with 103 additions and 1 deletion.
diff --git a/Source/Mosa.Compiler.Framework/InstructionNode.cs b/Source/Mosa.Compiler.Framework/InstructionNode.cs
@@ -873,6 +873,31 @@ public void ReplaceInstruction(BaseInstruction instruction)
 		Instruction = instruction;
 	}
 
+	public bool ContainsOperand(Operand operand)
+	{
+		foreach (var op in Operands)
+		{
+			if (op == operand)
+				return true;
+		}
+
+		return false;
+	}
+
+	public bool ContainsResult(Operand operand)
+	{
+		if (ResultCount == 0)
+			return false;
+
+		if (ResultCount >= 1 && Result == operand)
+			return true;
+
+		if (ResultCount == 2 && Result2 == operand)
+			return true;
+
+		return false;
+	}
+
 	#endregion Methods
 
 	#region Navigation

diff --git a/Source/Mosa.Compiler.Framework/Stages/ExitSSAStage.cs b/Source/Mosa.Compiler.Framework/Stages/ExitSSAStage.cs
@@ -12,10 +12,12 @@ namespace Mosa.Compiler.Framework.Stages;
 public class ExitSSAStage : BaseMethodCompilerStage
 {
 	private readonly Counter InstructionCount = new("ExitSSAStage.IRInstructions");
+	private readonly Counter MoveAvoidedCount = new("ExitSSAStage.MoveAvoided");
 
 	protected override void Initialize()
 	{
 		Register(InstructionCount);
+		Register(MoveAvoidedCount);
 	}
 
 	protected override void Run()
@@ -56,7 +58,7 @@ private void ProcessPhiInstruction(InstructionNode node)
 	{
 		var sourceBlocks = node.PhiBlocks;
 
-		for (var index = 0; index < node.Block.PreviousBlocks.Count; index++)
+		for (var index = 0; index < sourceBlocks.Count; index++)
 		{
 			var operand = node.GetOperand(index);
 			var predecessor = sourceBlocks[index];
@@ -78,6 +80,16 @@ private void InsertCopyStatement(BasicBlock predecessor, Operand destination, Op
 		if (destination == source)
 			return;
 
+		if (source.IsDefinedOnce && source.IsUsedOnce && source.Definitions[0].Block == predecessor)
+		{
+			if (destination.IsUsedOnce || CheckIfLast(predecessor, destination, source))
+			{
+				source.Definitions[0].Result = destination;
+				MoveAvoidedCount.Increment();
+				return;
+			}
+		}
+
 		var node = predecessor.BeforeLast;
 
 		while (node.Instruction != IRInstruction.Jmp)
@@ -96,4 +108,21 @@ private void InsertCopyStatement(BasicBlock predecessor, Operand destination, Op
 		var moveInstruction = MethodCompiler.GetMoveInstruction(destination.Primitive);
 		context.AppendInstruction(moveInstruction, destination, source);
 	}
+
+	private bool CheckIfLast(BasicBlock block, Operand stop, Operand okay)
+	{
+		for (var node = block.BeforeLast; !node.IsBlockStartInstruction; node = node.Previous)
+		{
+			if (node.IsEmptyOrNop)
+				continue;
+
+			if (node.ContainsOperand(stop))
+				return false;
+
+			if (node.ContainsOperand(okay))
+				return true;
+		}
+
+		return false;
+	}
 }
diff --git a/Source/Mosa.UnitTests/Optimization/LoopTests.cs b/Source/Mosa.UnitTests/Optimization/LoopTests.cs
@@ -0,0 +1,47 @@
+// Copyright (c) MOSA Project. Licensed under the New BSD License.
+
+namespace Mosa.UnitTests.Optimization;
+
+public static class LoopTests
+{
+	private static uint[] array = { 1, 2, 3, 4 };
+
+	[MosaUnitTest]
+	public static uint Loop0()
+	{
+		var x = 0u;
+
+		for (uint i = 0; i < 4; i++)
+		{
+			x += 2;
+		}
+
+		return x;
+	}
+
+	[MosaUnitTest]
+	public static uint Loop1()
+	{
+		var x = 0u;
+
+		for (uint i = 0; i < 4; i++)
+		{
+			x += i * 4 + 4;
+		}
+
+		return x;
+	}
+
+	[MosaUnitTest]
+	public static uint Loop2()
+	{
+		var x = 0u;
+
+		for (uint i = 0; i < 4; i++)
+		{
+			x += array[i];
+		}
+
+		return x;
+	}
+}
diff --git a/Source/Mosa.Utility.UnitTests/Mosa.Utility.UnitTests.csproj b/Source/Mosa.Utility.UnitTests/Mosa.Utility.UnitTests.csproj
@@ -47,6 +47,7 @@
 		<Compile Include="..\Mosa.UnitTests\Optimization\RemAndModTests.cs" Link="Tests\Optimization\RemAndModTests.cs" />
 		<Compile Include="..\Mosa.UnitTests\Optimization\SwitchTests.cs" Link="Tests\Optimization\SwitchTests.cs" />
 		<Compile Include="..\Mosa.UnitTests\Optimization\SpecificTests.cs" Link="Tests\Optimization\SpecificTests.cs" />
+		<Compile Include="..\Mosa.UnitTests\Optimization\LoopTests.cs" Link="Tests\Optimization\LoopTests.cs" />
 
 		<Compile Include="..\Mosa.UnitTests\Optimization\LoopUnrollingTests.cs" Link="Tests\Optimization\LoopUnrollingTests.cs" />