Re-enable the newly simplified ADCE.  This fixes a regression on
Dhrystone introduced by its removal.

llvm-svn: 51669
diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
index a37e899..19dcb2b 100644
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -296,7 +296,7 @@
   addPass(PM, createCondPropagationPass());      // Propagate conditionals
 
   addPass(PM, createDeadStoreEliminationPass()); // Delete dead stores
-  addPass(PM, createDeadCodeEliminationPass());                  // Delete dead instructions
+  addPass(PM, createAggressiveDCEPass());        // Delete dead instructions
   addPass(PM, createCFGSimplificationPass());    // Merge & remove BBs
   addPass(PM, createStripDeadPrototypesPass());  // Get rid of dead prototypes
   addPass(PM, createDeadTypeEliminationPass());  // Eliminate dead types