Add ability to use const expressions inside array initializers (#693)

* Add ability to use const expressions inside array initializers

Cesium.CodeGen.Tests/CodeGenArrayTests.cs

@@ -212,6 +212,17 @@ int main() {
         return 0;
     }
 
+    return 1;
+}");
+
+    [Fact]
+    public Task ArrayInitializerConstExpression() => DoTest(@"
+int main() {
+    int a[] = { -2, 99, 0, -743, 1+1, 2, 4 };
+    if (a[1] != 99) {
+        return 0;
+    }
+
     return 1;
 }");
 

Cesium.CodeGen.Tests/verified/CodeGenArrayTests.ArrayInitializerConstExpression.verified.txt

@@ -0,0 +1,39 @@
+System.Int32 <Module>::main()
+  Locals:
+    System.Int32* V_0
+  IL_0000: ldc.i4.s 28
+  IL_0002: conv.u
+  IL_0003: localloc
+  IL_0005: stloc.0
+  IL_0006: ldsflda <ConstantPool>/<ConstantPoolItemType28> <ConstantPool>::ConstDataBuffer0
+  IL_000b: ldloc V_0
+  IL_000f: ldc.i4.s 28
+  IL_0011: conv.u
+  IL_0012: call System.Void Cesium.Runtime.RuntimeHelpers::InitializeCompound(System.Void*,System.Void*,System.UInt32)
+  IL_0017: ldloc.0
+  IL_0018: ldc.i4.1
+  IL_0019: conv.i
+  IL_001a: ldc.i4 4
+  IL_001f: mul
+  IL_0020: add
+  IL_0021: ldind.i4
+  IL_0022: ldc.i4.s 99
+  IL_0024: ceq
+  IL_0026: ldc.i4.0
+  IL_0027: ceq
+  IL_0029: brfalse IL_0030
+  IL_002e: ldc.i4.0
+  IL_002f: ret
+  IL_0030: nop
+  IL_0031: ldc.i4.1
+  IL_0032: ret
+
+System.Int32 <Module>::<SyntheticEntrypoint>()
+  Locals:
+    System.Int32 V_0
+  IL_0000: call System.Int32 <Module>::main()
+  IL_0005: stloc.s V_0
+  IL_0007: ldloc.s V_0
+  IL_0009: call System.Void Cesium.Runtime.RuntimeHelpers::Exit(System.Int32)
+  IL_000e: ldloc.s V_0
+  IL_0010: ret

Cesium.CodeGen/Ir/Expressions/ArrayInitializerExpression.cs

@@ -25,6 +25,31 @@ public IType GetExpressionType(IDeclarationScope scope)
 
     public IExpression Lower(IDeclarationScope scope)
     {
-        throw new NotImplementedException();
+        return InlineConstantExpressions(scope);
+    }
+
+    public ArrayInitializerExpression InlineConstantExpressions(IDeclarationScope scope)
+    {
+        List<IExpression?> expressions = new();
+        foreach (var initializer in Initializers)
+        {
+            if (initializer is null)
+            {
+                expressions.Add(initializer);
+                continue;
+            }
+
+            var (errorMessage, constant) = ConstantEvaluator.TryGetConstantValue(initializer);
+            if (constant != null)
+            {
+                expressions.Add(new ConstantLiteralExpression(constant));
+            }
+            else
+            {
+                expressions.Add(initializer);
+            }
+        }
+
+        return new ArrayInitializerExpression(expressions.ToImmutableArray());
     }
 }

Cesium.CodeGen/Ir/Expressions/CompoundInitializationExpression.cs

@@ -107,5 +107,5 @@ void WriteValue(long value)
 
     public IType GetExpressionType(IDeclarationScope scope) => _type;
 
-    public IExpression Lower(IDeclarationScope scope) => new CompoundInitializationExpression(scope.ResolveType(_type), _arrayInitializer);
+    public IExpression Lower(IDeclarationScope scope) => new CompoundInitializationExpression(scope.ResolveType(_type), _arrayInitializer.InlineConstantExpressions(scope));
 }