Let binaryen split our memory data up

Author: geraintluff

src/compiler.ts

@@ -831,6 +831,11 @@ export class Compiler extends DiagnosticEmitter {
       }
     }
 
+    if (options.willOptimize) {
+      // Binaryen will split this up more efficiently
+      memorySegments = module.combineMemorySegments(memorySegments);
+    }
+
     // Setup internal memory with default name "0"
     module.setMemory(
       initialPages,

src/module.ts

@@ -2337,6 +2337,20 @@ export class Module {
   /** Unlimited memory constant. */
   static readonly UNLIMITED_MEMORY: Index = <Index>-1;
 
+  combineMemorySegments(
+    segments: MemorySegment[]
+  ) : MemorySegment[] {
+    if (!segments.length) return segments;
+    segments = segments.slice(0);
+    let lastSegment = segments[segments.length - 1];
+    let length = u32(lastSegment.offset) + lastSegment.buffer.length;
+    let newBuffer = new Uint8Array(u32(length));
+    segments.forEach(segment => {
+      newBuffer.set(segment.buffer, u32(segment.offset));
+    });
+    return [new MemorySegment(newBuffer, i64_new(0))];
+  }
+
   setMemory(
     initial: Index,
     maximum: Index,