do not do redundant llvm optimizations on bitcode; do them only when actually generating js

2 files changed, 17 insertions, 14 deletions

diff --git a/emcc b/emcc
index c4575310..4264020b 100755
--- a/emcc
+++ b/emcc
@@ -117,7 +117,10 @@ Options that are modified or new in %s include:
                            optimizations, and no runtime assertions
                            or C++ exception catching (to re-enable
                            C++ exception catching, use
-                           -s DISABLE_EXCEPTION_CATCHING=0 )
+                           -s DISABLE_EXCEPTION_CATCHING=0 ).
+                           Note: Optimizations are only done when
+                           compiling to JavaScript, not to intermediate
+                           bitcode.
   -O2                      As -O1, plus the relooper (loop recreation),
                            plus closure compiler advanced opts
                            Warning: Compiling with this takes a long time!
@@ -397,18 +400,10 @@ try:
           if DEBUG: print >> sys.stderr, 'emcc: assembling assembly file: ', input_file
           shared.Building.llvm_as(input_file, in_temp(unsuffixed_basename(input_file) + '.o'))
 
-  # Optimize, if asked to
-  if llvm_opt_level > 0 and not LEAVE_INPUTS_RAW:
-    if DEBUG: print >> sys.stderr, 'emcc: LLVM opts'
-    for input_file in input_files:
-      try:
-        shared.Building.llvm_opt(in_temp(unsuffixed_basename(input_file) + '.o'), LLVM_INTERNAL_OPT_LEVEL, safe=llvm_opt_level < 2)
-      except:
-        # This might be an invalid input, which will get ignored during linking later anyhow
-        print >> sys.stderr, 'emcc: warning: LLVM opt failed to run on %s, continuing without optimization' % input_file
-
   # If we were just asked to generate bitcode, stop there
   if final_suffix not in ['js', 'html']:
+    if llvm_opt_level > 0:
+      print >> sys.stderr, 'emcc: warning: -Ox flags ignored, since not generating JavaScript'
     if not specified_target:
       for input_file in input_files:
         shutil.move(in_temp(unsuffixed_basename(input_file) + '.o'), unsuffixed_basename(input_file) + '.' + final_suffix)
@@ -428,7 +423,7 @@ try:
 
   ## Continue on to create JavaScript
 
-  if DEBUG: print >> sys.stderr, 'emcc: generating JavaScript'
+  if DEBUG: print >> sys.stderr, 'emcc: will generate JavaScript'
 
   extra_files_to_link = []
 
@@ -473,10 +468,15 @@ try:
     if not LEAVE_INPUTS_RAW:
       shutil.move(in_temp(unsuffixed_basename(input_files[0]) + '.o'), in_temp(target_basename + '.bc'))
 
+  # Optimize, if asked to
+  if llvm_opt_level > 0 and not LEAVE_INPUTS_RAW:
+    if DEBUG: print >> sys.stderr, 'emcc: LLVM opts'
+    shared.Building.llvm_opt(in_temp(target_basename + '.bc'), LLVM_INTERNAL_OPT_LEVEL, safe=llvm_opt_level < 2)
+
   # Emscripten
   try:
     if shared.Settings.RELOOP:
-      print >> sys.stderr, 'Warning: The relooper optimization can be very slow.'
+      print >> sys.stderr, 'emcc: warning: The relooper optimization can be very slow.'
   except:
     pass
 
diff --git a/tests/runner.py b/tests/runner.py
index 34071a91..0f81d26d 100644
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -5311,6 +5311,7 @@ Options that are modified or new in %s include:
           (['-o', 'something.bc'], 1, ['-O1'], 0, 0),
           (['-o', 'something.bc'], 2, ['-O2'], 1, 0),
           (['-o', 'something.bc'], 3, ['-O3'], 1, 0),
+          (['-O1', '-o', 'something.bc'], 0, [], 0, 0), # -Ox is ignored and warned about
         ]:
           #print params, opt_level, bc_params, closure
           clear()
@@ -5318,10 +5319,12 @@ Options that are modified or new in %s include:
                          stdout=PIPE, stderr=PIPE).communicate()
           assert len(output[0]) == 0, output[0]
           if bc_params is not None:
+            if '-O1' in params and 'something.bc' in params:
+              assert 'warning: -Ox flags ignored, since not generating JavaScript' in output[1]
             assert os.path.exists('something.bc'), output[1]
             output = Popen([compiler, 'something.bc', '-o', 'something.js'] + bc_params, stdout=PIPE, stderr=PIPE).communicate()
           assert os.path.exists('something.js'), output[1]
-          assert ('Warning: The relooper optimization can be very slow.' in output[1]) == (opt_level >= 2), 'relooper warning should appear in opt >= 2'
+          assert ('warning: The relooper optimization can be very slow.' in output[1]) == (opt_level >= 2), 'relooper warning should appear in opt >= 2'
           assert ('Warning: Applying some potentially unsafe optimizations!' in output[1]) == (opt_level >= 3), 'unsafe warning should appear in opt >= 3'
           self.assertContained('hello, world!', run_js('something.js'))