Make DEAD_FUNCTIONS work, add test

emcc

@@ -1070,6 +1070,10 @@ try:
       memory_init_file = True
     assert closure is not 2, 'EMTERPRETIFY requires valid asm.js, and is incompatible with closure 2 which disables that'
 
+  if shared.Settings.DEAD_FUNCTIONS and not js_opts:
+    js_opts = True
+    logging.warning('enabling js opts for DEAD_FUNCTIONS')
+
   if proxy_to_worker:
     shared.Settings.PROXY_TO_WORKER = 1
 
@@ -1491,6 +1495,10 @@ try:
       js_optimizer_queue = []
     js_optimizer_extra_info = {}
 
+  if shared.Settings.DEAD_FUNCTIONS:
+    js_optimizer_queue += ['eliminateDeadFuncs']
+    js_optimizer_extra_info['dead_functions'] = shared.Settings.DEAD_FUNCTIONS
+
   if opt_level >= 1 and js_opts:
     logging.debug('running js post-opts')
 

tests/test_core.py

@@ -6125,6 +6125,38 @@ def process(filename):
       self.emcc_args += ['--closure', '1']
       self.do_run_from_file(src, output, post_build=post)
 
+  def test_dead_functions(self):
+    src = r'''
+      #include <stdio.h>
+      extern "C" {
+      __attribute__((noinline)) int unused(int x) {
+        return x;
+      }
+      }
+      int main(int argc, char **argv) {
+        printf("*%d*\n", argc > 1 ? unused(1) : 2);
+        return 0;
+      }
+    '''
+    def test(expected, args=[], no_build=False):
+      self.do_run(src, expected, args=args, no_build=no_build)
+      return open(self.in_dir('src.cpp.o.js')).read()
+
+    # Sanity check that it works and the dead function is emitted
+    js = test('*1*', ['x'])
+    test('*2*', no_build=True)
+    if self.run_name in ['default', 'asm1', 'asm2g']: assert 'function _unused($' in js
+
+    # Kill off the dead function, and check a code path using it aborts
+    Settings.DEAD_FUNCTIONS = ['_unused']
+    test('*2*')
+    test('abort(-1) at Error', args=['x'], no_build=True)
+
+    # Kill off a library function, check code aborts
+    Settings.DEAD_FUNCTIONS = ['_printf']
+    test('abort(-1) at Error')
+    test('abort(-1) at Error', args=['x'], no_build=True)
+
   def test_pgo(self):
     if Settings.ASM_JS: return self.skip('PGO does not work in asm mode')
 

tools/js-optimizer.js

@@ -7916,6 +7916,23 @@ 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 deadFunctions = set(extraInfo.dead_functions);
+  traverseGeneratedFunctions(ast, function (fun, type) {
+    if (!(fun[1] in deadFunctions)) {
+      return;
+    }
+    var asmData = normalizeAsm(fun);
+    fun[3] = [['stat', ['call', ['name', 'abort'], [['num', -1]]]]];
+    asmData.vars = {};
+    denormalizeAsm(fun, asmData);
+  });
+}
+
 // Passes table
 
 var minifyWhitespace = false, printMetadata = true, asm = false, asmPreciseF32 = false, emitJSON = false, last = false;
@@ -7936,6 +7953,7 @@ var passes = {
   loopOptimizer: loopOptimizer,
   registerize: registerize,
   registerizeHarder: registerizeHarder,
+  eliminateDeadFuncs: eliminateDeadFuncs,
   eliminate: eliminate,
   eliminateMemSafe: eliminateMemSafe,
   aggressiveVariableElimination: aggressiveVariableElimination,

tools/js_optimizer.py

@@ -9,7 +9,7 @@ __rootpath__ = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
 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 +3869,29 @@ 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));
+  StringSet deadFunctions;
+  for (size_t i = 0; i < extraInfo[DEAD_FUNCTIONS]->size(); i++) {
+    deadFunctions.insert(extraInfo[DEAD_FUNCTIONS][i]->getIString());
+  }
+  traverseFunctions(ast, [&](Ref fun) {
+    if (!deadFunctions.has(fun[1].get()->getIString())) {
+      return;
+    }
+    AsmData asmData(fun);
+    fun[3]->setSize(1);
+    fun[3][0] = make1(STAT, make2(CALL, makeName(ABORT), &(makeArray())->push_back(makeNum(-1))));
+    asmData.vars.clear();
+    asmData.denormalize();
+  });
+}
+
 //==================
 // Main
 //==================
@@ -3925,6 +3948,7 @@ 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);