Allow specifying LLVM args in target specifications

Author: Jethro Beekman

src/librustc_codegen_llvm/llvm_util.rs

@@ -46,7 +46,7 @@ fn require_inited() {
 }
 
 unsafe fn configure_llvm(sess: &Session) {
-    let n_args = sess.opts.cg.llvm_args.len();
+    let n_args = sess.opts.cg.llvm_args.len() + sess.target.target.options.llvm_args.len();
     let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
     let mut llvm_args = Vec::with_capacity(n_args + 1);
 
@@ -56,11 +56,11 @@ unsafe fn configure_llvm(sess: &Session) {
         full_arg.trim().split(|c: char| c == '=' || c.is_whitespace()).next().unwrap_or("")
     }
 
-    let user_specified_args: FxHashSet<_> = sess
-        .opts
-        .cg
-        .llvm_args
-        .iter()
+    let cg_opts = sess.opts.cg.llvm_args.iter();
+    let tg_opts = sess.target.target.options.llvm_args.iter();
+
+    let user_specified_args: FxHashSet<_> = cg_opts
+        .chain(tg_opts)
         .map(|s| llvm_arg_to_arg_name(s))
         .filter(|s| s.len() > 0)
         .collect();

src/librustc_target/spec/mod.rs

@@ -805,6 +805,9 @@ pub struct TargetOptions {
 
     /// Whether or not RelaxElfRelocation flag will be passed to the linker
     pub relax_elf_relocations: bool,
+
+    /// Additional arguments to pass to LLVM, similar to the `-C llvm-args` codegen option.
+    pub llvm_args: Vec<String>,
 }
 
 impl Default for TargetOptions {
@@ -893,6 +896,7 @@ impl Default for TargetOptions {
             target_mcount: "mcount".to_string(),
             llvm_abiname: "".to_string(),
             relax_elf_relocations: false,
+            llvm_args: vec![],
         }
     }
 }
@@ -1206,6 +1210,7 @@ impl Target {
         key!(target_mcount);
         key!(llvm_abiname);
         key!(relax_elf_relocations, bool);
+        key!(llvm_args, list);
 
         if let Some(array) = obj.find("abi-blacklist").and_then(Json::as_array) {
             for name in array.iter().filter_map(|abi| abi.as_string()) {
@@ -1433,6 +1438,7 @@ impl ToJson for Target {
         target_option_val!(target_mcount);
         target_option_val!(llvm_abiname);
         target_option_val!(relax_elf_relocations);
+        target_option_val!(llvm_args);
 
         if default.abi_blacklist != self.options.abi_blacklist {
             d.insert(