(#100) CodeGen: for loop statement

Cesium.CodeGen.Tests/CodeGenForTests.cs

@@ -0,0 +1,53 @@
+namespace Cesium.CodeGen.Tests;
+
+public class CodeGenForTests : CodeGenTestBase
+{
+    private static Task DoTest(string source)
+    {
+        var assembly = GenerateAssembly(default, source);
+
+        var moduleType = assembly.Modules.Single().GetType("<Module>");
+        return VerifyMethods(moduleType);
+    }
+
+    [Fact]
+    public Task SimpleFor() => DoTest(
+        @"int main()
+{
+    int i;
+    for(i = 0; i < 10; ++i) ++i;
+}");
+
+    [Fact]
+    public Task ForTest_NoInit() => DoTest(
+        @"int main()
+{
+    int i = 0;
+    for(; i < 10; ++i) ++i;
+}");
+
+
+    [Fact]
+    public Task For_NoTest() => DoTest(
+        @"int main()
+{
+    int i;
+    for(i = 0; ; ++i) ++i;
+}");
+
+    [Fact]
+    public Task For_NoUpdate() => DoTest(
+        @"int main()
+{
+    int i;
+    for(i = 0; i < 10; ) ++i;
+}");
+
+    [Fact]
+    public Task For_Empty() => DoTest(
+        @"int main()
+{
+    int i;
+    for(;;) ++i;
+}");
+}

Cesium.CodeGen.Tests/verified/CodeGenForTests.ForTest_NoInit.verified.txt

@@ -0,0 +1,18 @@
+System.Int32 <Module>::main()
+  Locals:
+    System.Int32 V_0
+  IL_0000: ldc.i4 0
+  IL_0005: stloc V_0
+  IL_0009: br IL_002a
+  IL_000e: ldloc V_0
+  IL_0012: ldc.i4 1
+  IL_0017: add
+  IL_0018: stloc V_0
+  IL_001c: ldloc V_0
+  IL_0020: ldc.i4 1
+  IL_0025: add
+  IL_0026: stloc V_0
+  IL_002a: ldloc V_0
+  IL_002e: ldc.i4 10
+  IL_0033: clt
+  IL_0035: brtrue IL_000e

Cesium.CodeGen.Tests/verified/CodeGenForTests.For_Empty.verified.txt

@@ -0,0 +1,10 @@
+System.Int32 <Module>::main()
+  Locals:
+    System.Int32 V_0
+  IL_0000: br IL_0013
+  IL_0005: ldloc V_0
+  IL_0009: ldc.i4 1
+  IL_000e: add
+  IL_000f: stloc V_0
+  IL_0013: ldc.i4 1
+  IL_0018: brtrue IL_0005

Cesium.CodeGen.Tests/verified/CodeGenForTests.For_NoTest.verified.txt

@@ -0,0 +1,16 @@
+System.Int32 <Module>::main()
+  Locals:
+    System.Int32 V_0
+  IL_0000: ldc.i4 0
+  IL_0005: stloc V_0
+  IL_0009: br IL_002a
+  IL_000e: ldloc V_0
+  IL_0012: ldc.i4 1
+  IL_0017: add
+  IL_0018: stloc V_0
+  IL_001c: ldloc V_0
+  IL_0020: ldc.i4 1
+  IL_0025: add
+  IL_0026: stloc V_0
+  IL_002a: ldc.i4 1
+  IL_002f: brtrue IL_000e

Cesium.CodeGen.Tests/verified/CodeGenForTests.For_NoUpdate.verified.txt

@@ -0,0 +1,14 @@
+System.Int32 <Module>::main()
+  Locals:
+    System.Int32 V_0
+  IL_0000: ldc.i4 0
+  IL_0005: stloc V_0
+  IL_0009: br IL_001c
+  IL_000e: ldloc V_0
+  IL_0012: ldc.i4 1
+  IL_0017: add
+  IL_0018: stloc V_0
+  IL_001c: ldloc V_0
+  IL_0020: ldc.i4 10
+  IL_0025: clt
+  IL_0027: brtrue IL_000e

Cesium.CodeGen.Tests/verified/CodeGenForTests.SimpleFor.verified.txt

@@ -0,0 +1,18 @@
+System.Int32 <Module>::main()
+  Locals:
+    System.Int32 V_0
+  IL_0000: ldc.i4 0
+  IL_0005: stloc V_0
+  IL_0009: br IL_002a
+  IL_000e: ldloc V_0
+  IL_0012: ldc.i4 1
+  IL_0017: add
+  IL_0018: stloc V_0
+  IL_001c: ldloc V_0
+  IL_0020: ldc.i4 1
+  IL_0025: add
+  IL_0026: stloc V_0
+  IL_002a: ldloc V_0
+  IL_002e: ldc.i4 10
+  IL_0033: clt
+  IL_0035: brtrue IL_000e

Cesium.CodeGen/Extensions/BlockItemEx.cs

@@ -18,6 +18,7 @@ internal static class BlockItemEx
         Ast.ReturnStatement s => new ReturnStatement(s),
         Ast.ExpressionStatement s => new ExpressionStatement(s),
         Ast.IfElseStatement s => new IfElseStatement(s),
+        Ast.ForStatement s => new ForStatement(s),
         _ => throw new NotImplementedException($"Statement not supported, yet: {blockItem}.")
     };
 }

Cesium.CodeGen/Ir/BlockItems/ForStatement.cs

@@ -0,0 +1,66 @@
+using Cesium.CodeGen.Contexts;
+using Cesium.CodeGen.Extensions;
+using Cesium.CodeGen.Ir.Expressions;
+using Cesium.CodeGen.Ir.Expressions.Constants;
+using Mono.Cecil.Cil;
+using ConstantExpression = Cesium.CodeGen.Ir.Expressions.ConstantExpression;
+
+namespace Cesium.CodeGen.Ir.BlockItems;
+
+internal class ForStatement : IBlockItem
+{
+    private readonly IExpression? _initExpression;
+    private readonly IExpression _testExpression;
+    private readonly IExpression? _updateExpression;
+    private readonly IBlockItem _body;
+
+    public ForStatement(Ast.ForStatement statement)
+    {
+        var (initExpression, testExpression, updateExpression, body) = statement;
+        _initExpression = initExpression?.ToIntermediate();
+        // 6.8.5.3.2 if testExpression is null it should be replaced by nonzero constant
+        _testExpression = testExpression?.ToIntermediate() ?? new ConstantExpression(new IntegerConstant("1"));
+        _updateExpression = updateExpression?.ToIntermediate();
+        _body = body.ToIntermediate();
+    }
+
+    private ForStatement(
+        IExpression? initExpression,
+        IExpression testExpression,
+        IExpression? updateExpression,
+        IBlockItem body)
+    {
+        _initExpression = initExpression;
+        _testExpression = testExpression;
+        _updateExpression = updateExpression;
+        _body = body;
+    }
+
+    public IBlockItem Lower()
+        => new ForStatement(
+            _initExpression?.Lower(),
+            _testExpression.Lower(),
+            _updateExpression?.Lower(),
+            _body.Lower());
+
+    public void EmitTo(FunctionScope scope)
+    {
+        var bodyProcessor = scope.Method.Body.GetILProcessor();
+        var instructions = bodyProcessor.Body.Instructions;
+        var stub = bodyProcessor.Create(OpCodes.Nop);
+
+        _initExpression?.EmitTo(scope);
+        var brToTest = bodyProcessor.Create(OpCodes.Br, stub);
+        bodyProcessor.Append(brToTest);
+        var loopStartIndex = instructions.Count;
+        _body.EmitTo(scope);
+        _updateExpression?.EmitTo(scope);
+        var testStartIndex = instructions.Count;
+        _testExpression.EmitTo(scope);
+        var testStart = instructions[testStartIndex];
+        brToTest.Operand = testStart;
+
+        var loopStart = instructions[loopStartIndex];
+        bodyProcessor.Emit(OpCodes.Brtrue, loopStart);
+    }
+}