Remove rustc_llvm dependency from librustc

Consequently, session creation can no longer initialize LLVM.
The few places that use the compiler without going through
rustc_driver/CompilerCalls thus need to be careful to manually
initialize LLVM (via rustc_trans!) immediately after session
creation.

This means librustc is not rebuilt when LLVM changes.

Author: Robin Kruppe

src/Cargo.lock

@@ -19,7 +19,6 @@ rustc_bitflags = { path = "../librustc_bitflags" }
 rustc_const_math = { path = "../librustc_const_math" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_errors = { path = "../librustc_errors" }
-rustc_llvm = { path = "../librustc_llvm" }
 serialize = { path = "../libserialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }

src/librustc/Cargo.toml

@@ -55,7 +55,6 @@ extern crate getopts;
 extern crate graphviz;
 extern crate libc;
 extern crate owning_ref;
-extern crate rustc_llvm as llvm;
 extern crate rustc_back;
 extern crate rustc_data_structures;
 extern crate serialize;

src/librustc/lib.rs

@@ -37,19 +37,16 @@ use syntax_pos::{Span, MultiSpan, FileMap};
 use rustc_back::{LinkerFlavor, PanicStrategy};
 use rustc_back::target::Target;
 use rustc_data_structures::flock;
-use llvm;
 
 use std::path::{Path, PathBuf};
 use std::cell::{self, Cell, RefCell};
 use std::collections::HashMap;
 use std::env;
-use std::ffi::CString;
 use std::io::Write;
 use std::rc::Rc;
 use std::fmt;
 use std::time::Duration;
 use std::sync::Arc;
-use libc::c_int;
 
 mod code_stats;
 pub mod config;
@@ -713,8 +710,6 @@ pub fn build_session_(sopts: config::Options,
         out_of_fuel: Cell::new(false),
     };
 
-    init_llvm(&sess);
-
     sess
 }
 
@@ -743,55 +738,6 @@ pub enum IncrCompSession {
     }
 }
 
-fn init_llvm(sess: &Session) {
-    unsafe {
-        // Before we touch LLVM, make sure that multithreading is enabled.
-        use std::sync::Once;
-        static INIT: Once = Once::new();
-        static mut POISONED: bool = false;
-        INIT.call_once(|| {
-            if llvm::LLVMStartMultithreaded() != 1 {
-                // use an extra bool to make sure that all future usage of LLVM
-                // cannot proceed despite the Once not running more than once.
-                POISONED = true;
-            }
-
-            configure_llvm(sess);
-        });
-
-        if POISONED {
-            bug!("couldn't enable multi-threaded LLVM");
-        }
-    }
-}
-
-unsafe fn configure_llvm(sess: &Session) {
-    let mut llvm_c_strs = Vec::new();
-    let mut llvm_args = Vec::new();
-
-    {
-        let mut add = |arg: &str| {
-            let s = CString::new(arg).unwrap();
-            llvm_args.push(s.as_ptr());
-            llvm_c_strs.push(s);
-        };
-        add("rustc"); // fake program name
-        if sess.time_llvm_passes() { add("-time-passes"); }
-        if sess.print_llvm_passes() { add("-debug-pass=Structure"); }
-
-        for arg in &sess.opts.cg.llvm_args {
-            add(&(*arg));
-        }
-    }
-
-    llvm::LLVMInitializePasses();
-
-    llvm::initialize_available_targets();
-
-    llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int,
-                                 llvm_args.as_ptr());
-}
-
 pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
     let emitter: Box<Emitter> = match output {
         config::ErrorOutputType::HumanReadable(color_config) => {

src/librustc/session/mod.rs

@@ -211,6 +211,7 @@ pub fn run_compiler<'a>(args: &[String],
     let mut sess = session::build_session_with_codemap(
         sopts, &dep_graph, input_file_path, descriptions, cstore.clone(), codemap, emitter_dest,
     );
+    rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
 
     let mut cfg = config::build_configuration(&sess, cfg);
@@ -415,6 +416,7 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
                     None,
                     descriptions.clone(),
                     cstore.clone());
+                rustc_trans::init(&sess);
                 rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
                 let mut cfg = config::build_configuration(&sess, cfg.clone());
                 target_features::add_configuration(&mut cfg, &sess);

src/librustc_driver/lib.rs

@@ -112,6 +112,7 @@ fn test_env<F>(source_string: &str,
                                        diagnostic_handler,
                                        Rc::new(CodeMap::new(FilePathMapping::empty())),
                                        cstore.clone());
+    rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
     let input = config::Input::Str {
         name: driver::anon_src(),

src/librustc_driver/test.rs

@@ -178,3 +178,55 @@ pub struct CrateTranslation {
 }
 
 __build_diagnostic_array! { librustc_trans, DIAGNOSTICS }
+
+use rustc::session::Session;
+pub fn init(sess: &Session) {
+    unsafe {
+        // Before we touch LLVM, make sure that multithreading is enabled.
+        use std::sync::Once;
+        static INIT: Once = Once::new();
+        static mut POISONED: bool = false;
+        INIT.call_once(|| {
+            if llvm::LLVMStartMultithreaded() != 1 {
+                // use an extra bool to make sure that all future usage of LLVM
+                // cannot proceed despite the Once not running more than once.
+                POISONED = true;
+            }
+
+            configure_llvm(sess);
+        });
+
+        if POISONED {
+            bug!("couldn't enable multi-threaded LLVM");
+        }
+    }
+}
+
+use std::ffi::CString;
+use libc::c_int;
+unsafe fn configure_llvm(sess: &Session) {
+    let mut llvm_c_strs = Vec::new();
+    let mut llvm_args = Vec::new();
+
+    {
+        let mut add = |arg: &str| {
+            let s = CString::new(arg).unwrap();
+            llvm_args.push(s.as_ptr());
+            llvm_c_strs.push(s);
+        };
+        add("rustc"); // fake program name
+        if sess.time_llvm_passes() { add("-time-passes"); }
+        if sess.print_llvm_passes() { add("-debug-pass=Structure"); }
+
+        for arg in &sess.opts.cg.llvm_args {
+            add(&(*arg));
+        }
+    }
+
+    llvm::LLVMInitializePasses();
+
+    llvm::initialize_available_targets();
+
+    llvm::LLVMRustSetLLVMOptions(llvm_args.len() as c_int,
+                                 llvm_args.as_ptr());
+}

src/librustc_trans/lib.rs

@@ -143,6 +143,7 @@ pub fn run_core(search_paths: SearchPaths,
     let mut sess = session::build_session_(
         sessopts, &dep_graph, cpath, diagnostic_handler, codemap, cstore.clone()
     );
+    rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
 
     let mut cfg = config::build_configuration(&sess, config::parse_cfgspecs(cfgs));

src/librustdoc/core.rs

@@ -86,6 +86,7 @@ pub fn run(input: &str,
     let mut sess = session::build_session_(
         sessopts, &dep_graph, Some(input_path.clone()), handler, codemap.clone(), cstore.clone(),
     );
+    rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
     sess.parse_sess.config =
         config::build_configuration(&sess, config::parse_cfgspecs(cfgs.clone()));
@@ -234,6 +235,7 @@ fn runtest(test: &str, cratename: &str, cfgs: Vec<String>, libs: SearchPaths,
     let mut sess = session::build_session_(
         sessopts, &dep_graph, None, diagnostic_handler, codemap, cstore.clone(),
     );
+    rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
 
     let outdir = Mutex::new(TempDir::new("rustdoctest").ok().expect("rustdoc needs a tempdir"));

src/librustdoc/test.rs

@@ -61,6 +61,7 @@ fn basic_sess(sysroot: PathBuf) -> (Session, Rc<CStore>) {
     let dep_graph = DepGraph::new(opts.build_dep_graph());
     let cstore = Rc::new(CStore::new(&dep_graph, Box::new(rustc_trans::LlvmMetadataLoader)));
     let sess = build_session(opts, &dep_graph, None, descriptions, cstore.clone());
+    rustc_trans::init(&sess);
     rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
     (sess, cstore)
 }