Enable -fno-plt by default and add tests

Author: GabrielMajeri

src/lib.rs

@@ -112,6 +112,7 @@ pub struct Build {
     archiver: Option<PathBuf>,
     cargo_metadata: bool,
     pic: Option<bool>,
+    use_plt: Option<bool>,
     static_crt: Option<bool>,
     shared_flag: Option<bool>,
     static_flag: Option<bool>,
@@ -319,6 +320,7 @@ impl Build {
             archiver: None,
             cargo_metadata: true,
             pic: None,
+            use_plt: None,
             static_crt: None,
             warnings: None,
             extra_warnings: None,
@@ -822,6 +824,25 @@ impl Build {
         self
     }
 
+    /// Configures whether the Procedure Linkage Table is used for indirect
+    /// calls into shared libraries.
+    ///
+    /// The PLT is used to provide features like lazy binding, but introduces
+    /// a small performance loss due to extra pointer indirection.
+    ///
+    /// Note that skipping the PLT requires a recent version of GCC/Clang,
+    /// therefore this option should only be considered a hint to disable the
+    /// PLT where supported.
+    ///
+    /// The PLT is disabled by default when PIC is enabled, with the exception
+    /// of `powerpc64-unknown-linux-gnu`.
+    ///
+    /// This only applies to ELF targets. It has no effect on other platforms.
+    pub fn use_plt(&mut self, use_plt: bool) -> &mut Build {
+        self.use_plt = Some(use_plt);
+        self
+    }
+
     /// Configures whether the /MT flag or the /MD flag will be passed to msvc build tools.
     ///
     /// This option defaults to `false`, and affect only msvc targets.
@@ -1123,6 +1144,11 @@ impl Build {
                 }
                 if self.pic.unwrap_or(!target.contains("windows-gnu")) {
                     cmd.push_cc_arg("-fPIC".into());
+                    if !self.use_plt.unwrap_or(target.contains("powerpc64-unknown-linux")) {
+                        if self.is_flag_supported("-fno-plt").unwrap_or(false) {
+                            cmd.push_cc_arg("-fno-plt".into());
+                        }
+                    }
                 }
             }
         }

tests/test.rs

@@ -197,6 +197,19 @@ fn gnu_i686_pic() {
     }
 }
 
+#[test]
+fn powerpc64_unknown_linux_use_plt() {
+    let target = "powerpc64-unknown-linux-gnu";
+    let test = Test::gnu();
+    test.gcc()
+        .pic(true)
+        .target(&target)
+        .host(&target)
+        .file("foo.c")
+        .compile("foo");
+    test.cmd(0).must_not_have("-fno-plt");
+}
+
 #[test]
 fn gnu_set_stdlib() {
     let test = Test::gnu();