emit ll from llvm opt directly, to skip writing and reading all the bitcode

2 files changed, 18 insertions, 8 deletions

diff --git a/emcc b/emcc
index 4c3aa009..c3f9d862 100755
--- a/emcc
+++ b/emcc
@@ -1638,18 +1638,26 @@ try:
     else:
       # At minimum remove dead functions etc., this potentially saves a lot in the size of the generated code (and the time to compile it)
       link_opts += shared.Building.get_safe_internalize() + ['-globaldce']
-    shared.Building.llvm_opt(in_temp(target_basename + '.bc'), link_opts)
-    if DEBUG: save_intermediate('linktime', 'bc')
+    if not save_bc:
+      # let llvm opt directly emit ll, to skip writing and reading all the bitcode
+      link_opts += ['-S']
+      shared.Building.llvm_opt(final, link_opts, final + '.link.ll')
+      final = final + '.link.ll'
+      if DEBUG: save_intermediate('linktime', 'll')
+    else:
+      shared.Building.llvm_opt(final, link_opts)
+      if DEBUG: save_intermediate('linktime', 'bc')
 
   if save_bc:
     shutil.copyfile(final, save_bc)
 
   # Prepare .ll for Emscripten
   if not LEAVE_INPUTS_RAW:
-    final = shared.Building.llvm_dis(final, final + '.ll')
+    if save_bc:
+      final = shared.Building.llvm_dis(final, final + '.ll')
   else:
     assert len(input_files) == 1
-  if DEBUG: save_intermediate('ll', 'll')
+  if DEBUG and save_bc: save_intermediate('ll', 'll')
 
   if AUTODEBUG:
     logging.debug('autodebug')
diff --git a/tools/shared.py b/tools/shared.py
index e2c6e89f..5b165b8b 100644
--- a/tools/shared.py
+++ b/tools/shared.py
@@ -1110,14 +1110,16 @@ class Building:
   # @param opt Either an integer, in which case it is the optimization level (-O1, -O2, etc.), or a list of raw
   #            optimization passes passed to llvm opt
   @staticmethod
-  def llvm_opt(filename, opts):
+  def llvm_opt(filename, opts, out=None):
     if type(opts) is int:
       opts = Building.pick_llvm_opts(opts)
     #opts += ['-debug-pass=Arguments']
     logging.debug('emcc: LLVM opts: ' + str(opts))
-    output = Popen([LLVM_OPT, filename] + opts + ['-o', filename + '.opt.bc'], stdout=PIPE).communicate()[0]
-    assert os.path.exists(filename + '.opt.bc'), 'Failed to run llvm optimizations: ' + output
-    shutil.move(filename + '.opt.bc', filename)
+    target = out or (filename + '.opt.bc')
+    output = Popen([LLVM_OPT, filename] + opts + ['-o', target], stdout=PIPE).communicate()[0]
+    assert os.path.exists(target), 'Failed to run llvm optimizations: ' + output
+    if not out:
+      shutil.move(filename + '.opt.bc', filename)
 
   @staticmethod
   def llvm_opts(filename): # deprecated version, only for test runner. TODO: remove