Auto merge of #41565 - rkruppe:llvm-sys, r=eddyb

Make only rustc_trans depend on rustc_llvm

With these changes, only rustc_trans depends directly on rustc_llvm (and no crate gained a new dependency on trans). This means changing LLVM doesn't rebuild librustc or rustc_metadata, only rustc_trans, rustc_driver and the rustc executable
Also, rustc_driver technically doesn't know about LLVM any more (of course, it still handles a ton of options that conceptually refer to LLVM, but it delegates their implementation to trans).

What I *didn't* implement was merging most or all of rustc_llvm into rustc_trans. I ran into a nasty bug, which was probably just a silly typo somewhere but I probably won't have the time to figure it out in the next week or two. I opened #41699 for that step.

Fixes #41473

src/librustc/Cargo.toml

@@ -13,12 +13,12 @@ arena = { path = "../libarena" }
 fmt_macros = { path = "../libfmt_macros" }
 graphviz = { path = "../libgraphviz" }
 log = "0.3"
+owning_ref = "0.3.3"
 rustc_back = { path = "../librustc_back" }
 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/lib.rs

@@ -54,7 +54,7 @@ extern crate fmt_macros;
 extern crate getopts;
 extern crate graphviz;
 extern crate libc;
-extern crate rustc_llvm as llvm;
+extern crate owning_ref;
 extern crate rustc_back;
 extern crate rustc_data_structures;
 extern crate serialize;

src/librustc/middle/cstore.rs

@@ -36,8 +36,9 @@ use session::search_paths::PathKind;
 use util::nodemap::{NodeSet, DefIdMap};
 
 use std::any::Any;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::rc::Rc;
+use owning_ref::ErasedBoxRef;
 use syntax::ast;
 use syntax::ext::base::SyntaxExtension;
 use syntax::symbol::Symbol;
@@ -201,11 +202,33 @@ impl EncodedMetadataHashes {
     }
 }
 
+/// The backend's way to give the crate store access to the metadata in a library.
+/// Note that it returns the raw metadata bytes stored in the library file, whether
+/// it is compressed, uncompressed, some weird mix, etc.
+/// rmeta files are backend independent and not handled here.
+///
+/// At the time of this writing, there is only one backend and one way to store
+/// metadata in library -- this trait just serves to decouple rustc_metadata from
+/// the archive reader, which depends on LLVM.
+pub trait MetadataLoader {
+    fn get_rlib_metadata(&self,
+                         target: &Target,
+                         filename: &Path)
+                         -> Result<ErasedBoxRef<[u8]>, String>;
+    fn get_dylib_metadata(&self,
+                          target: &Target,
+                          filename: &Path)
+                          -> Result<ErasedBoxRef<[u8]>, String>;
+}
+
 /// A store of Rust crates, through with their metadata
 /// can be accessed.
 pub trait CrateStore {
     fn crate_data_as_rc_any(&self, krate: CrateNum) -> Rc<Any>;
 
+    // access to the metadata loader
+    fn metadata_loader(&self) -> &MetadataLoader;
+
     // item info
     fn visibility(&self, def: DefId) -> ty::Visibility;
     fn visible_parent_map<'a>(&'a self) -> ::std::cell::Ref<'a, DefIdMap<DefId>>;
@@ -275,8 +298,6 @@ pub trait CrateStore {
     fn used_link_args(&self) -> Vec<String>;
 
     // utility functions
-    fn metadata_filename(&self) -> &str;
-    fn metadata_section_name(&self, target: &Target) -> &str;
     fn used_crates(&self, prefer: LinkagePreference) -> Vec<(CrateNum, LibSource)>;
     fn used_crate_source(&self, cnum: CrateNum) -> CrateSource;
     fn extern_mod_stmt_cnum(&self, emod_id: ast::NodeId) -> Option<CrateNum>;
@@ -413,8 +434,6 @@ impl CrateStore for DummyCrateStore {
     fn used_link_args(&self) -> Vec<String> { vec![] }
 
     // utility functions
-    fn metadata_filename(&self) -> &str { bug!("metadata_filename") }
-    fn metadata_section_name(&self, target: &Target) -> &str { bug!("metadata_section_name") }
     fn used_crates(&self, prefer: LinkagePreference) -> Vec<(CrateNum, LibSource)>
         { vec![] }
     fn used_crate_source(&self, cnum: CrateNum) -> CrateSource { bug!("used_crate_source") }
@@ -427,6 +446,9 @@ impl CrateStore for DummyCrateStore {
         bug!("encode_metadata")
     }
     fn metadata_encoding_version(&self) -> &[u8] { bug!("metadata_encoding_version") }
+
+    // access to the metadata loader
+    fn metadata_loader(&self) -> &MetadataLoader { bug!("metadata_loader") }
 }
 
 pub trait CrateLoader {

src/librustc/session/config.rs

@@ -328,7 +328,7 @@ top_level_options!(
     }
 );
 
-#[derive(Clone, PartialEq, Eq)]
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum PrintRequest {
     FileNames,
     Sysroot,

src/librustc/session/mod.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_driver/Cargo.toml

@@ -22,7 +22,6 @@ rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_errors = { path = "../librustc_errors" }
 rustc_incremental = { path = "../librustc_incremental" }
 rustc_lint = { path = "../librustc_lint" }
-rustc_llvm = { path = "../librustc_llvm" }
 rustc_metadata = { path = "../librustc_metadata" }
 rustc_mir = { path = "../librustc_mir" }
 rustc_passes = { path = "../librustc_passes" }