Run coalesce-locals after the final simplify-locals.

We now emit more sets and tees of if-elses from simplify-locals, and
coalesce-locals is necessary to remove them if they are ineffectual,
that is, if no get will read them.

Author: kripken

src/passes/pass.cpp

@@ -180,8 +180,11 @@ void PassRunner::addDefaultFunctionOptimizationPasses() {
   }
   add("coalesce-locals");
   add("simplify-locals");
-  add("vacuum"); // previous pass creates garbage
+  add("vacuum");
+  add("reorder-locals");
+  add("coalesce-locals");
   add("reorder-locals");
+  add("vacuum");
   if (options.optimizeLevel >= 3 || options.shrinkLevel >= 1) {
     add("code-folding");
   }