explicitly identify emscripten-generated functions (as opposed to library ones, or handwritten ones appended to the same file), and run eliminator only on those

4 files changed, 28 insertions, 12 deletions

diff --git a/src/jsifier.js b/src/jsifier.js
index bd432001..6cbc0eb9 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -931,7 +931,12 @@ function JSify(data, functionsOnly, givenFunctions, givenGlobalVariables) {
     }
     generated = generated.concat(itemsDict.function).concat(data.unparsedFunctions);
 
-    if (!mainPass) return generated.map(function(item) { return item.JS }).join('\n');
+    if (!mainPass) {
+      Functions.allIdents = Functions.allIdents.concat(itemsDict.function.map(function(func) {
+        return func.ident;
+      }));
+      return generated.map(function(item) { return item.JS }).join('\n');
+    }
 
     // We are ready to print out the data, but must do so carefully - we are
     // dealing with potentially *huge* strings. Convenient replacements and
@@ -967,6 +972,8 @@ function JSify(data, functionsOnly, givenFunctions, givenGlobalVariables) {
         print(Functions.generateIndexing()); // done last, as it may rely on aliases set in postsets
       print(postParts[1]);
     print(shellParts[1]);
+    // Print out some useful metadata (for additional optimizations later, like the eliminator)
+    print('// EMSCRIPTEN_GENERATED_FUNCTIONS: ' + JSON.stringify(Functions.allIdents) + '\n');
     return null;
   }
 
diff --git a/src/modules.js b/src/modules.js
index 3b370878..f04731f8 100644
--- a/src/modules.js
+++ b/src/modules.js
@@ -228,6 +228,9 @@ var Functions = {
   // All functions that will be implemented in this file
   implementedFunctions: null,
 
+  // All the function idents seen so far
+  allIdents: [],
+
   indexedFunctions: [0, 0], // Start at a non-0 (even, see below) value
 
   // Mark a function as needing indexing, and returns the index
diff --git a/tools/eliminator/eliminator-test.js b/tools/eliminator/eliminator-test.js
index 8a364c0a..d3ee88cb 100644
--- a/tools/eliminator/eliminator-test.js
+++ b/tools/eliminator/eliminator-test.js
@@ -91,3 +91,5 @@ function py() {
   var $8 = $4 + 12;
   HEAP[$8] = $7;
 }
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["f", "g", "h"]
+
diff --git a/tools/eliminator/eliminator.coffee b/tools/eliminator/eliminator.coffee
index c07e5974..891718e2 100644
--- a/tools/eliminator/eliminator.coffee
+++ b/tools/eliminator/eliminator.coffee
@@ -20,6 +20,10 @@
 uglify = require 'uglify-js'
 fs = require 'fs'
 
+# Functions which have been generated by Emscripten. We optimize only those.
+generatedFunctions = []
+GENERATED_FUNCTIONS_MARKER = '// EMSCRIPTEN_GENERATED_FUNCTIONS:'
+
 # Maximum number of uses to consider a variable not worth eliminating.
 MAX_USES = 3
 
@@ -79,6 +83,8 @@ traverse = (node, callback) ->
 # function/defun node and call run() to apply the optimization (in-place).
 class Eliminator
   constructor: (func) ->
+    @ident = func[1]
+
     # The statements of the function to analyze.
     @body = func[3]
 
@@ -107,7 +113,7 @@ class Eliminator
   #   @returns: The number of variables eliminated, or undefined if skipped.
   run: ->
     # Our optimization does not account for closures.
-    if @hasClosures @body then return undefined
+    if not @isGenerated then return undefined
 
     @calculateBasicVarStats()
     @analyzeInitialValues()
@@ -128,16 +134,8 @@ class Eliminator
     return eliminated
 
   # Determines if a function is Emscripten-generated.
-  hasClosures: ->
-    closureFound = false
-
-    traverse @body, (node, type) ->
-      if type in ['defun', 'function', 'with']
-        closureFound = true
-        return false
-      return undefined
-
-    return closureFound
+  isGenerated: ->
+    return @ident in generatedFunctions
 
   # Runs the basic variable scan pass. Fills the following member variables:
   #   isLocal
@@ -337,6 +335,12 @@ class Eliminator
 main = ->
   # Get the parse tree.
   src = fs.readFileSync('/dev/stdin').toString()
+
+  throw 'Cannot identify generated functions' if GENERATED_FUNCTIONS_MARKER in src
+  generatedFunctionsLine = src.split('\n').filter (line) ->
+    return line.indexOf(GENERATED_FUNCTIONS_MARKER) == 0
+  generatedFunctions = eval(generatedFunctionsLine[0].replace(GENERATED_FUNCTIONS_MARKER, ''))
+
   ast = uglify.parser.parse src
 
   # Run the eliminator on all functions.