From ca64b2bb8026fb4510696736d2d887e21ac2bfa3 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 28 Jan 2024 21:15:53 +0000
Subject: Zero out GC children with explicit memory stores

---
 .../compiler/patio/types/PatioOffsets.java         | 13 ++++++++
 .../compiler/shidtopatio/ShidToPatioGc.java        | 36 +++++++++++++++++++---
 .../compiler/shidtopatio/ShidToPatioVars.java      |  8 +++--
 3 files changed, 50 insertions(+), 7 deletions(-)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java b/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java
index f427bd41..5a3be3ff 100644
--- a/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java
+++ b/src/main/java/org/shedlang/compiler/patio/types/PatioOffsets.java
@@ -1,11 +1,24 @@
 package org.shedlang.compiler.patio.types;
 
 import org.pcollections.PVector;
+import org.pcollections.TreePVector;
+
+import java.util.List;
 
 public class PatioOffsets {
     private PatioOffsets() {
     }
 
+    public static PatioDataLayout offsetDataLayout(
+        PatioDataLayout patioDataLayout,
+        List<Integer> patioOffsets
+    ) {
+        return offsetDataLayout(
+            patioDataLayout,
+            TreePVector.from(patioOffsets)
+        );
+    }
+
     public static PatioDataLayout offsetDataLayout(
         PatioDataLayout patioDataLayout,
         PVector<Integer> patioOffsets
diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java
index 351dee49..4bb7c3a3 100644
--- a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioGc.java
@@ -3,11 +3,10 @@ package org.shedlang.compiler.shidtopatio;
 import org.shedlang.compiler.patio.PatioFunctionDeclaration;
 import org.shedlang.compiler.patio.PatioLocal;
 import org.shedlang.compiler.patio.instructions.PatioCall;
-import org.shedlang.compiler.patio.operands.PatioInt32Const;
-import org.shedlang.compiler.patio.operands.PatioIntConst;
-import org.shedlang.compiler.patio.operands.PatioLocalRef;
-import org.shedlang.compiler.patio.operands.PatioOperand;
+import org.shedlang.compiler.patio.instructions.PatioMemoryStore;
+import org.shedlang.compiler.patio.operands.*;
 import org.shedlang.compiler.patio.types.*;
+import org.shedlang.compiler.patio.values.PatioDataPtrValueNull;
 import org.shedlang.compiler.patio.values.PatioIntValueByteOffsetOf;
 import org.shedlang.compiler.patio.values.PatioIntValueByteSizeOf;
 import org.shedlang.compiler.sources.Source;
@@ -154,12 +153,39 @@ public class ShidToPatioGc {
 
         var offset = new PatioInt32Const(new PatioIntValueByteOffsetOf(layout, childrenOffset));
 
-        return context.addInstruction(new PatioCall(
+        context = context.addInstruction(new PatioCall(
             Optional.of(destination),
             ALLOC.name(),
             List.of(size, offset, PatioInt32Const.of(childrenCount)),
             source
         ));
+
+        for (var childIndex = 0; childIndex < childrenCount; childIndex++) {
+            var childOffset = Lists.concat(childrenOffset, List.of(childIndex));
+            var childDataLayout = PatioOffsets.offsetDataLayout(layout, childOffset);
+
+            var zero = switch (childDataLayout) {
+                case PatioDataLayoutDataPtr patioDataLayoutDataPtr ->
+                    new PatioDataPtrConst(new PatioDataPtrValueNull());
+
+                case PatioDataLayoutInt dataLayoutInt ->
+                    PatioIntConst.of(0);
+
+                default ->
+                    // TODO: better error
+                    throw new IllegalArgumentException("unsupported child");
+            };
+
+            context = context.addInstruction(new PatioMemoryStore(
+                destination,
+                layout,
+                childOffset,
+                zero,
+                source
+            ));
+        }
+
+        return context;
     }
 
     // == Collection  ==
diff --git a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java
index 37e30123..34143882 100644
--- a/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java
+++ b/src/main/java/org/shedlang/compiler/shidtopatio/ShidToPatioVars.java
@@ -16,9 +16,13 @@ public class ShidToPatioVars {
     }
 
     private static final PatioDataLayout VAR_DATA_LAYOUT =
-        ShidToPatioGc.gcObjectDataLayout(PatioDataLayouts.fromType(ShidToPatioTypes.VALUE_TYPE));
+        ShidToPatioGc.gcObjectDataLayout(
+            PatioDataLayouts.struct(List.of(
+                PatioDataLayouts.fromType(ShidToPatioTypes.VALUE_TYPE)
+            ))
+        );
 
-    private static final List<Integer> VALUE_OFFSET = ShidToPatioGc.gcObjectOffset(List.of());
+    private static final List<Integer> VALUE_OFFSET = ShidToPatioGc.gcObjectOffset(List.of(0));
     private static final List<Integer> GC_CHILDREN_OFFSET = ShidToPatioGc.gcObjectOffset(List.of());
     private static final int GC_CHILDREN_COUNT = 1;
 
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