Revert "[BACKEND] Various bug fixes; making reductions faster (#533)".

This is a more stable commit that produce bitwise identical code to earlier
versions. Using commits after this one may lead to slightly different numerics

lib/codegen/pass.cc

@@ -88,7 +88,6 @@ std::unique_ptr<llvm::Module> add_passes_to_emit_bin(ir::module &ir, llvm::LLVMC
   allocation.run(ir);
   prefetch_s.run(ir);
   barriers.run(ir);
-  // ir.print(std::cout);
   isel.visit(ir, *llvm);
   shared_static = allocation.allocated_size();
   return llvm;