From b81f97cd01753eabe3722b8a9211e4f3f8d621ef Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 16 Mar 2025 14:32:10 +0000
Subject: Garbage collect arrays

---
 .../shidtopatio/ArrayBuilderRuntimeType.java       | 35 ++++++++++++++++++++++
 .../compiler/shidtopatio/ArrayRuntimeType.java     | 30 +++++++++++++++++++
 .../compiler/shidtopatio/ShidToPatioContext.java   |  7 +++++
 3 files changed, 72 insertions(+)
 create mode 100644 src/main/java/org/shedlang/compiler/shidtopatio/ArrayBuilderRuntimeType.java
 create mode 100644 src/main/java/org/shedlang/compiler/shidtopatio/ArrayRuntimeType.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ArrayBuilderRuntimeType.java b/src/main/java/org/shedlang/compiler/shidtopatio/ArrayBuilderRuntimeType.java
new file mode 100644
index 00000000..5cb8000a
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ArrayBuilderRuntimeType.java
@@ -0,0 +1,35 @@
+package org.shedlang.compiler.shidtopatio;
+
+import org.shedlang.compiler.patio.types.PatioDataLayout;
+import org.shedlang.compiler.patio.types.PatioDataLayouts;
+
+import java.util.List;
+
+public class ArrayBuilderRuntimeType implements RuntimeType {
+    public static final ArrayBuilderRuntimeType INSTANCE = new ArrayBuilderRuntimeType();
+
+    private ArrayBuilderRuntimeType() {
+    }
+
+    @Override
+    public PatioDataLayout layout() {
+        return ShidToPatioGc.gcObjectDataLayout(
+            PatioDataLayouts.struct(List.of(
+                PatioDataLayouts.INT,
+                PatioDataLayouts.INT,
+                PatioDataLayouts.INT,
+                PatioDataLayouts.BOOL
+            ))
+        );
+    }
+
+    @Override
+    public List<Integer> gcChildrenOffset() {
+        return ShidToPatioGc.gcObjectOffset(List.of());
+    }
+
+    @Override
+    public int gcChildrenCount() {
+        return 1;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ArrayRuntimeType.java b/src/main/java/org/shedlang/compiler/shidtopatio/ArrayRuntimeType.java
new file mode 100644
index 00000000..bc977526
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ArrayRuntimeType.java
@@ -0,0 +1,30 @@
+package org.shedlang.compiler.shidtopatio;
+
+import org.shedlang.compiler.patio.types.PatioDataLayout;
+import org.shedlang.compiler.patio.types.PatioDataLayouts;
+
+import java.util.List;
+
+public class ArrayRuntimeType implements RuntimeType {
+    public static final ArrayRuntimeType INSTANCE = new ArrayRuntimeType();
+
+    private ArrayRuntimeType() {
+    }
+
+    @Override
+    public PatioDataLayout layout() {
+        // TODO: separate out runtime type from the info needed by RTTI
+        return PatioDataLayouts.struct(List.of());
+    }
+
+    @Override
+    public List<Integer> gcChildrenOffset() {
+        return List.of();
+    }
+
+    @Override
+    public int gcChildrenCount() {
+        // This is a lie! We special case arrays in the runtime.
+        return 0;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioContext.java b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioContext.java
index 546a6ccd..87e5ff61 100644
--- a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioContext.java
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioContext.java
@@ -48,6 +48,13 @@ public record ShidToPatioContext(
             // Ensure that scalars have tag of 0: this is relied on in the
             // runtime (for instance, when allocating ints and strings).
             context = context.addRuntimeTypeTag(ScalarRuntimeType.INSTANCE);
+
+            // Ensure that arrays have tag of 1.
+            context = context.addRuntimeTypeTag(ArrayRuntimeType.INSTANCE);
+
+            // Ensure that array builders have tag of 2.
+            context = context.addRuntimeTypeTag(ArrayBuilderRuntimeType.INSTANCE);
+
             context = generateStructTags(context);
             context = generateEffectTags(context);
 
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