Switch pass order (#205).

The current order of passes in the frontend leads to issues due to the
expansion of switches and the introduction of branching instructions,
potentially leading to dead cycles.

This commit delays the dead cycles pass until after the switch pass
(remove switch constructions).

frontend/llvm/src/ikos_pp.cpp

@@ -266,12 +266,12 @@ int main(int argc, char** argv) {
     // Dead code elimination (opt -dce)
     pass_manager.add(llvm::createDeadCodeEliminationPass());
 
-    // Remove unreachable blocks also dead cycles
-    pass_manager.add(ikos_pp::create_remove_unreachable_blocks_pass());
-
     // Remove switch constructions (opt -lowerswitch)
     pass_manager.add(llvm::createLowerSwitchPass());
 
+    // Remove unreachable blocks also dead cycles
+    pass_manager.add(ikos_pp::create_remove_unreachable_blocks_pass());
+
     // Lower down atomic instructions (opt -loweratomic)
     pass_manager.add(llvm::createLowerAtomicPass());