From f4a0159dc00fd1caa7a251d7f6bcd23948cf5f7d Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 16 Dec 2023 15:50:49 +0000
Subject: Store namespace fields as permanent GC roots

---
 ...mpiler.testing.snapshots.Snapshotter)].expected |  7 ++++++
 .../shedlang/compiler/patio/PatioCodeGenGc.java    | 29 ++++++++++++++++++++++
 .../compiler/patio/PatioCodeGenNamespaces.java     |  2 ++
 3 files changed, 38 insertions(+)

diff --git a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.patio.PatioCodeGenNamespaceFieldStoreTests]/[method:canGenerateCodeForNamespaceFieldStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.patio.PatioCodeGenNamespaceFieldStoreTests]/[method:canGenerateCodeForNamespaceFieldStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
index 03399c60..2408d323 100644
--- a/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.patio.PatioCodeGenNamespaceFieldStoreTests]/[method:canGenerateCodeForNamespaceFieldStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
+++ b/snapshots/[engine:junit-jupiter]/[class:org.shedlang.compiler.patio.PatioCodeGenNamespaceFieldStoreTests]/[method:canGenerateCodeForNamespaceFieldStore(org.shedlang.compiler.testing.snapshots.Snapshotter)].expected
@@ -1,5 +1,11 @@
 Compilation unit elements:
 
+(
+    function-decl
+    "shed__runtime__gc_add_perm_root"
+    params=((param "gc_root" int))
+    return-type=void
+)
 
 Locals:
 
@@ -13,6 +19,7 @@ Instructions:
         offset=(1)
         value=(local "b")
     )
+    (call _ "shed__runtime__gc_add_perm_root" ((local "b")))
 )
 
 Temporary stack:
diff --git a/src/main/java/org/shedlang/compiler/patio/PatioCodeGenGc.java b/src/main/java/org/shedlang/compiler/patio/PatioCodeGenGc.java
index 4e12e531..144cf49b 100644
--- a/src/main/java/org/shedlang/compiler/patio/PatioCodeGenGc.java
+++ b/src/main/java/org/shedlang/compiler/patio/PatioCodeGenGc.java
@@ -1,11 +1,25 @@
 package org.shedlang.compiler.patio;
 
+import org.shedlang.compiler.patio.ast.PatioFunctionDeclaration;
+import org.shedlang.compiler.patio.ast.PatioLocal;
+import org.shedlang.compiler.patio.ast.instructions.PatioCall;
+import org.shedlang.compiler.patio.ast.operands.PatioOperand;
 import org.shedlang.compiler.patio.ast.types.*;
+import org.shedlang.compiler.sources.Source;
+import org.shedlang.compiler.sources.Sources;
 import org.shedlang.compiler.util.Lists;
 
 import java.util.List;
+import java.util.Optional;
 
 public class PatioCodeGenGc {
+    private static final PatioFunctionDeclaration ADD_PERM_GC_ROOT = new PatioFunctionDeclaration(
+        "shed__runtime__gc_add_perm_root",
+        List.of(PatioLocal.param("gc_root", PatioCodeGenTypes.VALUE_TYPE)),
+        PatioTypes.VOID,
+        Sources.RUNTIME
+    );
+
     private PatioCodeGenGc() {
     }
 
@@ -41,4 +55,19 @@ public class PatioCodeGenGc {
             value
         ));
     }
+
+    public static PatioCodeGenContext addPermGcRoot(
+        PatioOperand gcRoot,
+        Source source,
+        PatioCodeGenContext context
+    ) {
+        return context
+            .ensureCompilationUnitElement(ADD_PERM_GC_ROOT)
+            .addInstruction(new PatioCall(
+                Optional.empty(),
+                ADD_PERM_GC_ROOT.name(),
+                List.of(gcRoot),
+                source
+            ));
+    }
 }
diff --git a/src/main/java/org/shedlang/compiler/patio/PatioCodeGenNamespaces.java b/src/main/java/org/shedlang/compiler/patio/PatioCodeGenNamespaces.java
index 8bbf4e8b..280575bc 100644
--- a/src/main/java/org/shedlang/compiler/patio/PatioCodeGenNamespaces.java
+++ b/src/main/java/org/shedlang/compiler/patio/PatioCodeGenNamespaces.java
@@ -219,6 +219,8 @@ public class PatioCodeGenNamespaces {
             source
         ));
 
+        context = PatioCodeGenGc.addPermGcRoot(fieldValue, source, context);
+
         return context;
     }
 
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