Fix conditions for using legacy or new pm plugins

Author: eskarn

Diff for: compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -123,7 +123,7 @@ unsafe fn configure_llvm(sess: &Session) {
         sess.opts.debugging_opts.new_llvm_pass_manager.unwrap_or(false);
 
     // Use the legacy pm registration if the new_llvm_pass_manager option isn't explicitly enabled
-    if use_new_llvm_pm_plugin_register {
+    if !use_new_llvm_pm_plugin_register {
         // Register LLVM plugins by loading them into the compiler process.
         for plugin in &sess.opts.debugging_opts.llvm_plugins {
             let lib = Library::new(plugin).unwrap_or_else(|e| bug!("couldn't load plugin: {}", e));

Diff for: compiler/rustc_codegen_ssa/src/back/write.rs

@@ -261,7 +261,11 @@ impl ModuleConfig {
             inline_threshold: sess.opts.cg.inline_threshold,
             new_llvm_pass_manager: sess.opts.debugging_opts.new_llvm_pass_manager,
             emit_lifetime_markers: sess.emit_lifetime_markers(),
-            llvm_plugins: if_regular!(sess.opts.debugging_opts.llvm_plugins.clone(), vec![]),
+            llvm_plugins: if sess.opts.debugging_opts.new_llvm_pass_manager.unwrap_or(false) {
+                if_regular!(sess.opts.debugging_opts.llvm_plugins.clone(), vec![])
+            } else {
+                vec![]
+            },
         }
     }