Add command line parameter --no-heap-copy that optimizes for small memory footprint and fread() performance over the default behavior that copied VFS to HEAP, that is designed for mmap() performance.

Adjust MEMFS node contentMode enum to reflect whether content is off the main HEAP or not. Note that this enum is not much used, so this has little effect. Add browser tests to check that fread() and mmap() work with and without --no-heap-copy.

1 files changed, 6 insertions, 0 deletions

diff --git a/emcc b/emcc
index 3406ff83..8f8ad4aa 100755
--- a/emcc
+++ b/emcc
@@ -777,6 +777,7 @@ try:
   save_bc = False
   memory_init_file = False
   use_preload_cache = False
+  no_heap_copy = False
   proxy_to_worker = False
 
   if use_cxx:
@@ -897,6 +898,9 @@ try:
     elif newargs[i].startswith('--use-preload-cache'):
       use_preload_cache = True
       newargs[i] = ''
+    elif newargs[i].startswith('--no-heap-copy'):
+      no_heap_copy = True
+      newargs[i] = ''
     elif newargs[i] == '--ignore-dynamic-linking':
       ignore_dynamic_linking = True
       newargs[i] = ''
@@ -1667,6 +1671,8 @@ try:
       file_args += ['--compress', Compression.encoder, Compression.decoder, Compression.js_name]
     if use_preload_cache:
       file_args.append('--use-preload-cache')
+    if no_heap_copy:
+      file_args.append('--no-heap-copy')
     file_code = execute([shared.PYTHON, shared.FILE_PACKAGER, unsuffixed(target) + '.data'] + file_args, stdout=PIPE)[0]
     pre_js = file_code + pre_js