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

2 files changed, 17 insertions, 11 deletions

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.