Optimize allocations

decode.go

@@ -48,26 +48,15 @@ func decode(r io.Reader, configOnly bool) (image.Image, image.Config, error) {
 		return nil, cfg, ErrMemWrite
 	}
 
-	res, err = _alloc.Call(ctx, 4)
+	res, err = _alloc.Call(ctx, 4*3)
 	if err != nil {
 		return nil, cfg, fmt.Errorf("alloc: %w", err)
 	}
-	widthPtr := res[0]
-	defer _free.Call(ctx, widthPtr)
-
-	res, err = _alloc.Call(ctx, 4)
-	if err != nil {
-		return nil, cfg, fmt.Errorf("alloc: %w", err)
-	}
-	heightPtr := res[0]
-	defer _free.Call(ctx, heightPtr)
+	defer _free.Call(ctx, res[0])
 
-	res, err = _alloc.Call(ctx, 4)
-	if err != nil {
-		return nil, cfg, fmt.Errorf("alloc: %w", err)
-	}
-	stridePtr := res[0]
-	defer _free.Call(ctx, stridePtr)
+	widthPtr := res[0]
+	heightPtr := res[0] + 4
+	stridePtr := res[0] + 8
 
 	res, err = _decode.Call(ctx, inPtr, uint64(inSize), 1, widthPtr, heightPtr, stridePtr, 0)
 	if err != nil {