Clean up encoding of memories

captbaritone · Jun 6, 2020 · b3900b7 · b3900b7
1 parent 5b7219e
commit b3900b7
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Showing 3 changed files with 17 additions and 7 deletions.
diff --git a/packages/compiler/src/compiler.ts b/packages/compiler/src/compiler.ts
@@ -13,6 +13,9 @@ import {
   TYPE_IDX,
   EXPORT_TYPE,
   SECTION,
+  MEMORY_IDX,
+  MAGIC,
+  WASM_VERSION,
 } from "./encoding";
 import shims from "./shims";
 import { localFuncMap } from "./wasmFunctions";
@@ -184,7 +187,11 @@ export function compileModule({
 
   const memories = [
     // Only one memory
-    [...unsignedLEB128(0), ...unsignedLEB128(WASM_MEMORY_SIZE)],
+    [
+      0x01, // Indicates that we are specifying two values (initial/max)
+      ...unsignedLEB128(WASM_MEMORY_SIZE), // Initial size
+      ...unsignedLEB128(WASM_MEMORY_SIZE), // Max size
+    ],
   ];
 
   // https://webassembly.github.io/spec/core/binary/modules.html#global-section
@@ -219,12 +226,11 @@ export function compileModule({
     // the binary functions can be skipped efficiently.
     return encodeVector([...encodeVector(localTypes), ...func.binary, op.end]);
   });
-
   return new Uint8Array([
     // Magic module header
-    ...[0x00, 0x61, 0x73, 0x6d],
+    ...MAGIC,
     // Version number
-    ...[0x01, 0x00, 0x00, 0x00],
+    ...WASM_VERSION,
     ...encodeSection(SECTION.TYPE, types),
     ...encodeSection(SECTION.IMPORT, imports),
     ...encodeSection(SECTION.FUNC, functions),

diff --git a/packages/compiler/src/encoding.ts b/packages/compiler/src/encoding.ts
@@ -1,6 +1,9 @@
 import * as ieee754 from "./ieee754";
 import { flattenTwice } from "./arrayUtils";
 
+export const MAGIC = [0x00, 0x61, 0x73, 0x6d];
+export const WASM_VERSION = [0x01, 0x00, 0x00, 0x00];
+
 export const EPSILON = 0.00001;
 
 // An intial attempt to construct a Wasm binary by hand.
@@ -189,6 +192,7 @@ export type BlockType = typeof BLOCK[BlockKeys];
 // http://webassembly.github.io/spec/core/binary/types.html#function-types
 export const FUNCTION_TYPE = 0x60;
 // I think these might actually be specific to importdesc
+export const MEMORY_IDX = 0x02;
 export const GLOBAL_TYPE = 0x03;
 export const TYPE_IDX = 0x00;
 

diff --git a/packages/compiler/tools/testCases.ts b/packages/compiler/tools/testCases.ts
@@ -126,10 +126,10 @@ const testCases: [string, string, number][] = [
   ["Greater than or equal (false)", "g = 1 >= 2;", 0],
   ["Script without trailing semi", "g = 1", 1],
   ["Megabuf access", "g = megabuf(1);", 0],
-  // ["Max index megabuf", "megabuf(8388608) = 10; g = megabuf(8388608);", 10],
-  // ["Max index + 1 megabuf", "megabuf(8388609) = 10; g = megabuf(8388609);", 0],
+  ["Max index megabuf", "megabuf(8388608) = 10; g = megabuf(8388608);", 10],
+  ["Max index + 1 megabuf", "megabuf(8388609) = 10; g = megabuf(8388609);", 0],
   // ["Max index gmegabuf", " g = gmegabuf(8388608);", 10],
-  // ["Max index+1 gmegabuf", "gmegabuf(8388609) = 10; g = gmegabuf(8388609);", 0],
+  ["Max index+1 gmegabuf", "gmegabuf(8388609) = 10; g = gmegabuf(8388609);", 0],
   ["Megabuf assignment", "megabuf(1) = 10; g = megabuf(1);", 10],
   ["Megabuf assignment (idx 100)", "megabuf(100) = 10; g = megabuf(100);", 10],
   ["Megabuf (float)", "megabuf(0) = 1.2; g = megabuf(0);", 1.2],