Rename flag to -Z plt

Author: GabrielMajeri

src/librustc/session/config.rs

@@ -1387,9 +1387,10 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "output a json file with profiler results"),
     emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],
           "emits a section containing stack size metadata"),
-    no_plt: Option<bool> = (None, parse_opt_bool, [TRACKED],
-          "skip the PLT when calling into ELF shared libraries
-          (default: true if full relro is also enabled)"),
+    plt: Option<bool> = (Some(false), parse_opt_bool, [TRACKED],
+          "whether to use the PLT when calling into shared libraries;
+          only has effect for PIC code on systems with ELF binaries
+          (default: PLT is disabled if full relro is enabled)"),
 }
 
 pub fn default_lib_output() -> CrateType {

src/librustc_codegen_llvm/attributes.rs

@@ -174,7 +174,7 @@ pub fn from_fn_attrs(
     set_frame_pointer_elimination(cx, llfn);
     set_probestack(cx, llfn);
 
-    if cx.sess().opts.debugging_opts.no_plt.unwrap_or(true) {
+    if !cx.sess().opts.debugging_opts.plt.unwrap_or(false) {
         // Only enable this optimization if full relro is also enabled.
         // In this case, lazy binding was already unavailable, so nothing is lost.
         if let RelroLevel::Full = cx.sess().target.target.options.relro_level {

src/librustc_codegen_llvm/context.rs

@@ -210,7 +210,7 @@ pub unsafe fn create_module(
 
     // If skipping the PLT is enabled, we need to add some module metadata
     // to ensure intrinsic calls don't use it.
-    if sess.opts.debugging_opts.no_plt.unwrap_or(true) {
+    if !sess.opts.debugging_opts.plt.unwrap_or(false) {
         let avoid_plt = "RtLibUseGOT\0".as_ptr() as *const _;
         llvm::LLVMRustAddModuleFlag(llmod, avoid_plt, 1);
     }

src/test/codegen/no-plt.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: -C relocation-model=pic -Z no-plt
+// compile-flags: -C relocation-model=pic -Z plt=no
 
 #![crate_type = "lib"]