Add a native and non-native pass to remove dead functions

emcc

@@ -1491,6 +1491,13 @@ try:
       js_optimizer_queue = []
     js_optimizer_extra_info = {}
 
+  # Regardless of what -OX mode we're in, dead functions should be removed. This pass
+  # should be considered first so other optimisations aren't taken along for the ride.
+  if shared.Settings.DEAD_FUNCTIONS:
+    js_optimizer_queue += ['eliminateDeadFuncs']
+    js_optimizer_extra_info['dead_functions'] = shared.Settings.DEAD_FUNCTIONS
+    flush_js_optimizer_queue()
+
   if opt_level >= 1 and js_opts:
     logging.debug('running js post-opts')
 

emscripten.py

@@ -814,44 +814,6 @@ def emscript_fast(infile, settings, outfile, libraries=[], compiler_engine=None,
     #if DEBUG: print >> sys.stderr, "META", metadata
     #if DEBUG: print >> sys.stderr, "meminit", mem_init
 
-    # Strip functions to exclude from LLVM output
-    # This must be done as soon as possible, before we build function tables
-    # based on the functions in the js
-    rmfuncs = set(settings['DEAD_FUNCTIONS'])
-    if len(rmfuncs) > 0:
-        if DEBUG: logging.debug('Checking for dead functions')
-        funclines = funcs.split('\n')
-        new_funclines = []
-        infunc = False
-        shouldrm = False
-        for i, line in enumerate(funclines):
-          # The only lines we don't add are the *body* of the removed function -
-          # they get replaced by a comment, an abort and (if appropriate) a
-          # return value.
-          if shouldrm and not line.startswith('}'):
-            continue
-          new_funclines.append(line)
-          if line.startswith('function '):
-            assert not infunc
-            infunc = True
-            funcname = line[len('function '):line.index('(')]
-            if funcname in rmfuncs:
-              if DEBUG: logging.debug('  Stripping ' + funcname)
-              shouldrm = True
-              # Add parameter type hints to comply with asm.js
-              num_params = line.count('$')
-              new_funclines.extend(funclines[i+1:i+1+num_params])
-              # New body of function
-              new_funclines.append('/* Dead function %s stripped */' % (funcname,))
-              new_funclines.append('_abort();')
-          elif line.startswith('}'):
-            assert infunc
-            # If the original function had a return, make a return
-            if shouldrm and funclines[i-1].strip().startswith('return '):
-                new_funclines.insert(-1, 'return 0;')
-            infunc = shouldrm = False
-        funcs = '\n'.join(new_funclines)
-
     # if emulating pointer casts, force all tables to the size of the largest
     if settings['EMULATE_FUNCTION_POINTER_CASTS']:
       max_size = 0

tests/test_core.py

@@ -6140,13 +6140,12 @@ def test(expected, args=[], no_build=False):
     # Sanity check that it works and the dead function is emitted
     js = test('*1*', ['x'])
     test('*2*', no_build=True)
-    if has_comments: assert 'function _unused($' in js
+    if self.run_name in ['default', 'asm1', 'asm2g']: assert 'function _unused($' in js
 
     # Kill off the dead function, still works and is emitted as a stub
     Settings.DEAD_FUNCTIONS = ['_unused']
 
     js = test('*2*')
-    if has_comments: assert 'Dead function _unused stripped' in js # stub comment
 
     # Run the same code with argc that uses the dead function, see abort
     test('abort() at Error', args=['x'], no_build=True)

tools/js-optimizer.js

@@ -7911,6 +7911,26 @@ function asmLastOpts(ast) {
   });
 }
 
+// Contrary to the name this does not eliminate actual dead functions, only
+// those marked as such with DEAD_FUNCTIONS
+function eliminateDeadFuncs(ast) {
+  assert(asm);
+  assert(extraInfo && extraInfo.dead_functions);
+  var dead_functions = extraInfo.dead_functions;
+  traverseGeneratedFunctions(ast, function (fun, type) {
+    for (var i = 0; i < dead_functions.length; i++) {
+        if (dead_functions[i] === fun[1]) {
+            break;
+        }
+        return;
+    }
+    var asmData = normalizeAsm(fun);
+    fun[3] = [['stat', ['call', ['name', 'abort'], []]]];
+    asmData.vars = {};
+    denormalizeAsm(fun, asmData);
+  });
+}
+
 // Passes table
 
 var minifyWhitespace = false, printMetadata = true, asm = false, asmPreciseF32 = false, emitJSON = false, last = false;
@@ -7931,6 +7951,7 @@ var passes = {
   loopOptimizer: loopOptimizer,
   registerize: registerize,
   registerizeHarder: registerizeHarder,
+  eliminateDeadFuncs: eliminateDeadFuncs,
   eliminate: eliminate,
   eliminateMemSafe: eliminateMemSafe,
   aggressiveVariableElimination: aggressiveVariableElimination,

tools/js_optimizer.py

@@ -9,7 +9,7 @@
 def path_from_root(*pathelems):
   return os.path.join(__rootpath__, *pathelems)
 
-NATIVE_PASSES = set(['asm', 'asmPreciseF32', 'receiveJSON', 'emitJSON', 'eliminate', 'eliminateMemSafe', 'simplifyExpressions', 'simplifyIfs', 'optimizeFrounds', 'registerize', 'registerizeHarder', 'minifyNames', 'minifyLocals', 'minifyWhitespace', 'cleanup', 'asmLastOpts', 'last', 'noop', 'closure'])
+NATIVE_PASSES = set(['asm', 'asmPreciseF32', 'receiveJSON', 'emitJSON', 'eliminateDeadFuncs', 'eliminate', 'eliminateMemSafe', 'simplifyExpressions', 'simplifyIfs', 'optimizeFrounds', 'registerize', 'registerizeHarder', 'minifyNames', 'minifyLocals', 'minifyWhitespace', 'cleanup', 'asmLastOpts', 'last', 'noop', 'closure'])
 
 JS_OPTIMIZER = path_from_root('tools', 'js-optimizer.js')
 

tools/optimizer/optimizer.cpp

@@ -3869,6 +3869,31 @@ void asmLastOpts(Ref ast) {
   });
 }
 
+// Contrary to the name this does not eliminate actual dead functions, only
+// those marked as such with DEAD_FUNCTIONS
+void eliminateDeadFuncs(Ref ast) {
+  assert(!!extraInfo);
+  IString DEAD_FUNCTIONS("dead_functions");
+  IString ABORT("abort");
+  assert(extraInfo->has(DEAD_FUNCTIONS));
+  Ref dead_functions = extraInfo[DEAD_FUNCTIONS];
+  traverseFunctions(ast, [&](Ref fun) {
+    for (size_t i = 0; i < dead_functions->size(); i++) {
+        if (dead_functions[i] == fun[1].get()->getCString()) {
+            break;
+        }
+        return;
+    }
+    AsmData asmData(fun);
+    fun[3]->setSize(1);
+    fun[3][0] = make1(STAT, make2(CALL, makeName(ABORT), makeArray()));
+    while (asmData.vars.size() > 0) {
+      asmData.deleteVar(asmData.vars[0]);
+    }
+    asmData.denormalize();
+  });
+}
+
 //==================
 // Main
 //==================
@@ -3925,6 +3950,7 @@ int main(int argc, char **argv) {
     if (str == "asm") {} // the default for us
     else if (str == "asmPreciseF32") {}
     else if (str == "receiveJSON" || str == "emitJSON") {}
+    else if (str == "eliminateDeadFuncs") eliminateDeadFuncs(doc);
     else if (str == "eliminate") eliminate(doc);
     else if (str == "eliminateMemSafe") eliminateMemSafe(doc);
     else if (str == "simplifyExpressions") simplifyExpressions(doc);