From 978d93cccaa4d69bcd1810b46a30606d514e870f Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 24 Jun 2023 18:47:09 +0100
Subject: WASM binary format: support global imports

---
 .../compiler/backends/wasm/structure/WasmBinaryFormat.java  | 13 +++++++++++++
 .../wasm/structure/ast/imports/WasmImportDescriptor.java    |  2 ++
 .../backends/wasm/structure/ast/types/WasmGlobalType.java   |  4 ++++
 .../backends/wasm/structure/ast/types/WasmMutability.java   |  6 ++++++
 4 files changed, 25 insertions(+)
 create mode 100644 src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmGlobalType.java
 create mode 100644 src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmMutability.java

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/WasmBinaryFormat.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/WasmBinaryFormat.java
index 714f1936..b21ea2a0 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/structure/WasmBinaryFormat.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/WasmBinaryFormat.java
@@ -109,6 +109,10 @@ public class WasmBinaryFormat {
                 writer.writeByte(0x02);
                 writeMemoryType(memory.type(), writer);
             }
+            case WasmImportDescriptor.Global global -> {
+                writer.writeByte(0x03);
+                writeGlobalType(global.type(), writer);
+            }
         }
     }
 
@@ -159,6 +163,15 @@ public class WasmBinaryFormat {
         writeLimits(type.limits(), writer);
     }
 
+    private static void writeGlobalType(WasmGlobalType type, BinaryWriter writer) {
+        writeValueType(type.valueType(), writer);
+        var mutabilityEncoding = switch (type.mutability()) {
+            case MUTABLE -> 0x01;
+            case IMMUTABLE -> 0x00;
+        };
+        writer.writeByte(mutabilityEncoding);
+    }
+
     private static void writeReferenceType(WasmReferenceType type, BinaryWriter writer) {
         var encoding = switch (type) {
             case FUNC_REF -> 0x70;
diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/imports/WasmImportDescriptor.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/imports/WasmImportDescriptor.java
index e0bdc456..c9e6ba5f 100644
--- a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/imports/WasmImportDescriptor.java
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/imports/WasmImportDescriptor.java
@@ -1,6 +1,7 @@
 package org.shedlang.compiler.backends.wasm.structure.ast.imports;
 
 import org.shedlang.compiler.backends.wasm.structure.ast.types.WasmFuncType;
+import org.shedlang.compiler.backends.wasm.structure.ast.types.WasmGlobalType;
 import org.shedlang.compiler.backends.wasm.structure.ast.types.WasmMemoryType;
 import org.shedlang.compiler.backends.wasm.structure.ast.types.WasmTableType;
 
@@ -8,4 +9,5 @@ public sealed interface WasmImportDescriptor {
     record Func(String identifier, WasmFuncType type) implements WasmImportDescriptor {}
     record Table(WasmTableType type) implements WasmImportDescriptor {}
     record Memory(WasmMemoryType type) implements WasmImportDescriptor {}
+    record Global(WasmGlobalType type) implements WasmImportDescriptor {}
 }
diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmGlobalType.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmGlobalType.java
new file mode 100644
index 00000000..5d328f36
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmGlobalType.java
@@ -0,0 +1,4 @@
+package org.shedlang.compiler.backends.wasm.structure.ast.types;
+
+public record WasmGlobalType(WasmValueType valueType, WasmMutability mutability) {
+}
diff --git a/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmMutability.java b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmMutability.java
new file mode 100644
index 00000000..afc9962f
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/backends/wasm/structure/ast/types/WasmMutability.java
@@ -0,0 +1,6 @@
+package org.shedlang.compiler.backends.wasm.structure.ast.types;
+
+public enum WasmMutability {
+    MUTABLE,
+    IMMUTABLE,
+}
-- 
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