From e139747e1593885bc90f2ae5427a6215475b76fd Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 25 Jun 2023 12:38:32 +0100
Subject: Support globals in WASM binary format

---
 .../wasm/structure/ast/modules/WasmGlobal.java     |  7 +++
 .../wasm/structure/ast/modules/WasmModule.java     | 20 +++++++
 .../structure/binary/WasmBinaryFormatModules.java  | 62 +++++++++++++++-------
 3 files changed, 71 insertions(+), 18 deletions(-)
 create mode 100644 src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmGlobal.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmGlobal.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmGlobal.java
new file mode 100644
index 00000000..637376c2
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmGlobal.java
@@ -0,0 +1,7 @@
+package org.shedlang.compiler.backends.wasm.structure.ast.modules;
+
+import org.shedlang.compiler.backends.wasm.structure.ast.instructions.WasmExpression;
+import org.shedlang.compiler.backends.wasm.structure.ast.types.WasmGlobalType;
+
+public record WasmGlobal(WasmGlobalType type, WasmExpression init) {
+}
diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmModule.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmModule.java
index 7395d996..79a1e6f5 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmModule.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/modules/WasmModule.java
@@ -13,6 +13,7 @@ public record WasmModule(
     PVector<WasmFunction> functions,
     PVector<WasmTable> tables,
     PVector<WasmMemory> memories,
+    PVector<WasmGlobal> globals,
     PVector<WasmElementSegment> elementSegments,
     PVector<WasmImport> imports
 ) {
@@ -22,6 +23,7 @@ public record WasmModule(
         P.vector(),
         P.vector(),
         P.vector(),
+        P.vector(),
         P.vector()
     );
 
@@ -83,6 +85,7 @@ public record WasmModule(
             functions,
             tables,
             memories,
+            globals,
             elementSegments,
             imports
         );
@@ -94,6 +97,7 @@ public record WasmModule(
             functions.plus(function),
             tables,
             memories,
+            globals,
             elementSegments,
             imports
         );
@@ -105,6 +109,7 @@ public record WasmModule(
             functions,
             tables.plus(table),
             memories,
+            globals,
             elementSegments,
             imports
         );
@@ -116,6 +121,19 @@ public record WasmModule(
             functions,
             tables,
             memories.plus(memory),
+            globals,
+            elementSegments,
+            imports
+        );
+    }
+
+    public WasmModule addGlobal(WasmGlobal global) {
+        return new WasmModule(
+            types,
+            functions,
+            tables,
+            memories,
+            globals.plus(global),
             elementSegments,
             imports
         );
@@ -127,6 +145,7 @@ public record WasmModule(
             functions,
             tables,
             memories,
+            globals,
             elementSegments.plus(elementSegment),
             imports
         );
@@ -145,6 +164,7 @@ public record WasmModule(
             functions,
             tables,
             memories,
+            globals,
             elementSegments,
             newImports
         );
diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryFormatModules.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryFormatModules.java
index ef1c6afb..3525bbe5 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryFormatModules.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/binary/WasmBinaryFormatModules.java
@@ -207,6 +207,49 @@ public class WasmBinaryFormatModules {
         writeTableType(table.type(), writer);
     }
 
+    // == Memory Section ==
+
+    private static void writeMemorySection(WasmModule module, BinaryWriter writer) throws IOException {
+        if (module.memories().size() > 0) {
+            writeSection(SectionId.MEMORY, writer, () -> {
+                writeVec(
+                    module.memories(),
+                    memory -> writeMemory(memory, writer),
+                    writer
+                );
+            });
+        }
+    }
+
+    private static void writeMemory(WasmMemory memory, BinaryWriter writer) {
+        writeMemoryType(memory.type(), writer);
+    }
+
+    // == Global Section ==
+
+    private static void writeGlobalSection(
+        WasmModule module,
+        BinaryWriter writer
+    ) throws IOException {
+        if (module.globals().size() > 0) {
+            writeSection(SectionId.GLOBAL, writer, () -> {
+                writeVec(
+                    module.globals(),
+                    global -> writeGlobal(global, writer),
+                    writer
+                );
+            });
+        }
+    }
+
+    private static void writeGlobal(
+        WasmGlobal global,
+        BinaryWriter writer
+    ) throws IOException {
+        writeGlobalType(global.type(), writer);
+        writeExpression(global.init(), writer);
+    }
+
     // == Element Section ==
 
     private static void writeElementSection(
@@ -269,24 +312,6 @@ public class WasmBinaryFormatModules {
         writeExpression(function.body(), writer);
     }
 
-    // == Memory Section ==
-
-    private static void writeMemorySection(WasmModule module, BinaryWriter writer) throws IOException {
-        if (module.memories().size() > 0) {
-            writeSection(SectionId.MEMORY, writer, () -> {
-                writeVec(
-                    module.memories(),
-                    memory -> writeMemory(memory, writer),
-                    writer
-                );
-            });
-        }
-    }
-
-    private static void writeMemory(WasmMemory memory, BinaryWriter writer) {
-        writeMemoryType(memory.type(), writer);
-    }
-
     // == Modules ==
 
     private static final byte[] WASM_MAGIC = HexFormat.of().parseHex("0061736D");
@@ -303,6 +328,7 @@ public class WasmBinaryFormatModules {
         writeFunctionSection(module, indexTable, writer);
         writeTableSection(module, writer);
         writeMemorySection(module, writer);
+        writeGlobalSection(module, writer);
         writeElementSection(module, writer);
         writeCodeSection(module, writer);
         writeNameSection(module, indexTable, writer);
-- 
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