Auto merge of #53356 - michaelwoerister:itlto, r=alexcrichton

Preliminary work for incremental ThinLTO (CGU name edition)

Bring back the first half of #52266 but hopefully without the performance regression.

5 files changed, 31 insertions, 61 deletions

diff --git a/src/librustc_codegen_llvm/back/link.rs b/src/librustc_codegen_llvm/back/link.rs
index bbe1ccf3696..37c99932f56 100644
--- a/src/librustc_codegen_llvm/back/link.rs
+++ b/src/librustc_codegen_llvm/back/link.rs
@@ -46,13 +46,6 @@ use std::process::{Output, Stdio};
 use std::str;
 use syntax::attr;
 
-/// The LLVM module name containing crate-metadata. This includes a `.` on
-/// purpose, so it cannot clash with the name of a user-defined module.
-pub const METADATA_MODULE_NAME: &'static str = "crate.metadata";
-
-// same as for metadata above, but for allocator shim
-pub const ALLOCATOR_MODULE_NAME: &'static str = "crate.allocator";
-
 pub use rustc_codegen_utils::link::{find_crate_name, filename_for_input, default_output_for_target,
                                   invalid_output_for_target, build_link_meta, out_filename,
                                   check_file_is_writeable};
diff --git a/src/librustc_codegen_llvm/back/lto.rs b/src/librustc_codegen_llvm/back/lto.rs
index d7741230327..56858a31efd 100644
--- a/src/librustc_codegen_llvm/back/lto.rs
+++ b/src/librustc_codegen_llvm/back/lto.rs
@@ -242,7 +242,7 @@ fn fat_lto(cgcx: &CodegenContext,
             let llvm = module.llvm().expect("can't lto pre-codegened modules");
             (&llvm.llcx, llvm.llmod())
         };
-        info!("using {:?} as a base module", module.llmod_id);
+        info!("using {:?} as a base module", module.name);
 
         // The linking steps below may produce errors and diagnostics within LLVM
         // which we'd like to handle and print, so set up our diagnostic handlers
@@ -257,7 +257,7 @@ fn fat_lto(cgcx: &CodegenContext,
         for module in modules {
             let llvm = module.llvm().expect("can't lto pre-codegened modules");
             let buffer = ModuleBuffer::new(llvm.llmod());
-            let llmod_id = CString::new(&module.llmod_id[..]).unwrap();
+            let llmod_id = CString::new(&module.name[..]).unwrap();
             serialized_modules.push((SerializedModule::Local(buffer), llmod_id));
         }
 
@@ -384,9 +384,9 @@ fn thin_lto(diag_handler: &Handler,
         //        the most expensive portion of this small bit of global
         //        analysis!
         for (i, module) in modules.iter().enumerate() {
-            info!("local module: {} - {}", i, module.llmod_id);
+            info!("local module: {} - {}", i, module.name);
             let llvm = module.llvm().expect("can't lto precodegened module");
-            let name = CString::new(module.llmod_id.clone()).unwrap();
+            let name = CString::new(module.name.clone()).unwrap();
             let buffer = ThinBuffer::new(llvm.llmod());
             thin_modules.push(llvm::ThinLTOModule {
                 identifier: name.as_ptr(),
@@ -395,7 +395,7 @@ fn thin_lto(diag_handler: &Handler,
             });
             thin_buffers.push(buffer);
             module_names.push(name);
-            timeline.record(&module.llmod_id);
+            timeline.record(&module.name);
         }
 
         // FIXME: All upstream crates are deserialized internally in the
@@ -668,7 +668,6 @@ impl ThinModule {
                 llcx,
                 tm,
             }),
-            llmod_id: self.name().to_string(),
             name: self.name().to_string(),
             kind: ModuleKind::Regular,
         };
diff --git a/src/librustc_codegen_llvm/back/write.rs b/src/librustc_codegen_llvm/back/write.rs
index d60983d7697..b62836ec255 100644
--- a/src/librustc_codegen_llvm/back/write.rs
+++ b/src/librustc_codegen_llvm/back/write.rs
@@ -728,7 +728,7 @@ unsafe fn codegen(cgcx: &CodegenContext,
 
             if config.emit_bc_compressed {
                 let dst = bc_out.with_extension(RLIB_BYTECODE_EXTENSION);
-                let data = bytecode::encode(&module.llmod_id, data);
+                let data = bytecode::encode(&module.name, data);
                 if let Err(e) = fs::write(&dst, data) {
                     diag_handler.err(&format!("failed to write bytecode: {}", e));
                 }
@@ -1338,7 +1338,6 @@ fn execute_work_item(cgcx: &CodegenContext,
         assert_eq!(bytecode_compressed.is_some(), config.emit_bc_compressed);
 
         Ok(WorkItemResult::Compiled(CompiledModule {
-            llmod_id: module.llmod_id.clone(),
             name: module_name,
             kind: ModuleKind::Regular,
             pre_existing: true,
diff --git a/src/librustc_codegen_llvm/base.rs b/src/librustc_codegen_llvm/base.rs
index 7ca6a89dd9b..e626cc3870f 100644
--- a/src/librustc_codegen_llvm/base.rs
+++ b/src/librustc_codegen_llvm/base.rs
@@ -36,7 +36,7 @@ use metadata;
 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use rustc::middle::lang_items::StartFnLangItem;
 use rustc::middle::weak_lang_items;
-use rustc::mir::mono::{Linkage, Visibility, Stats};
+use rustc::mir::mono::{Linkage, Visibility, Stats, CodegenUnitNameBuilder};
 use rustc::middle::cstore::{EncodedMetadata};
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::layout::{self, Align, TyLayout, LayoutOf};
@@ -742,19 +742,23 @@ pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
     let crate_hash = tcx.crate_hash(LOCAL_CRATE);
     let link_meta = link::build_link_meta(crate_hash);
+    let cgu_name_builder = &mut CodegenUnitNameBuilder::new(tcx);
 
     // Codegen the metadata.
     tcx.sess.profiler(|p| p.start_activity(ProfileCategory::Codegen));
-    let llmod_id = "metadata";
-    let metadata_llvm_module = ModuleLlvm::new(tcx.sess, llmod_id);
+
+    let metadata_cgu_name = cgu_name_builder.build_cgu_name(LOCAL_CRATE,
+                                                            &["crate"],
+                                                            Some("metadata")).as_str()
+                                                                             .to_string();
+    let metadata_llvm_module = ModuleLlvm::new(tcx.sess, &metadata_cgu_name);
     let metadata = time(tcx.sess, "write metadata", || {
         write_metadata(tcx, &metadata_llvm_module, &link_meta)
     });
     tcx.sess.profiler(|p| p.end_activity(ProfileCategory::Codegen));
 
     let metadata_module = ModuleCodegen {
-        name: link::METADATA_MODULE_NAME.to_string(),
-        llmod_id: llmod_id.to_string(),
+        name: metadata_cgu_name,
         source: ModuleSource::Codegened(metadata_llvm_module),
         kind: ModuleKind::Metadata,
     };
@@ -833,20 +837,22 @@ pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let allocator_module = if any_dynamic_crate {
         None
     } else if let Some(kind) = *tcx.sess.allocator_kind.get() {
-        unsafe {
-            let llmod_id = "allocator";
-            let modules = ModuleLlvm::new(tcx.sess, llmod_id);
-            time(tcx.sess, "write allocator module", || {
+        let llmod_id = cgu_name_builder.build_cgu_name(LOCAL_CRATE,
+                                                       &["crate"],
+                                                       Some("allocator")).as_str()
+                                                                         .to_string();
+        let modules = ModuleLlvm::new(tcx.sess, &llmod_id);
+        time(tcx.sess, "write allocator module", || {
+            unsafe {
                 allocator::codegen(tcx, &modules, kind)
-            });
+            }
+        });
 
-            Some(ModuleCodegen {
-                name: link::ALLOCATOR_MODULE_NAME.to_string(),
-                llmod_id: llmod_id.to_string(),
-                source: ModuleSource::Codegened(modules),
-                kind: ModuleKind::Allocator,
-            })
-        }
+        Some(ModuleCodegen {
+            name: llmod_id,
+            source: ModuleSource::Codegened(modules),
+            kind: ModuleKind::Allocator,
+        })
     } else {
         None
     };
@@ -889,21 +895,10 @@ pub fn codegen_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 // succeed it means that none of the dependencies has changed
                 // and we can safely re-use.
                 if let Some(dep_node_index) = tcx.dep_graph.try_mark_green(tcx, dep_node) {
-                    // Append ".rs" to LLVM module identifier.
-                    //
-                    // LLVM code generator emits a ".file filename" directive
-                    // for ELF backends. Value of the "filename" is set as the
-                    // LLVM module identifier.  Due to a LLVM MC bug[1], LLVM
-                    // crashes if the module identifier is same as other symbols
-                    // such as a function name in the module.
-                    // 1. http://llvm.org/bugs/show_bug.cgi?id=11479
-                    let llmod_id = format!("{}.rs", cgu.name());
-
                     let module = ModuleCodegen {
                         name: cgu.name().to_string(),
                         source: ModuleSource::Preexisting(buf),
                         kind: ModuleKind::Regular,
-                        llmod_id,
                     };
                     tcx.dep_graph.mark_loaded_from_cache(dep_node_index, true);
                     write::submit_codegened_module_to_llvm(tcx, module, 0);
@@ -1212,21 +1207,8 @@ fn compile_codegen_unit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     {
         let cgu_name = cgu.name().to_string();
 
-        // Append ".rs" to LLVM module identifier.
-        //
-        // LLVM code generator emits a ".file filename" directive
-        // for ELF backends. Value of the "filename" is set as the
-        // LLVM module identifier.  Due to a LLVM MC bug[1], LLVM
-        // crashes if the module identifier is same as other symbols
-        // such as a function name in the module.
-        // 1. http://llvm.org/bugs/show_bug.cgi?id=11479
-        let llmod_id = format!("{}-{}.rs",
-                               cgu.name(),
-                               tcx.crate_disambiguator(LOCAL_CRATE)
-                                   .to_fingerprint().to_hex());
-
         // Instantiate monomorphizations without filling out definitions yet...
-        let llvm_module = ModuleLlvm::new(tcx.sess, &llmod_id);
+        let llvm_module = ModuleLlvm::new(tcx.sess, &cgu_name);
         let stats = {
             let cx = CodegenCx::new(tcx, cgu, &llvm_module);
             let mono_items = cx.codegen_unit
@@ -1282,7 +1264,6 @@ fn compile_codegen_unit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             name: cgu_name,
             source: ModuleSource::Codegened(llvm_module),
             kind: ModuleKind::Regular,
-            llmod_id,
         })
     }
 }
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index 390a1df02b8..a65511a24af 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -269,8 +269,8 @@ struct ModuleCodegen {
     /// unique amongst **all** crates.  Therefore, it should contain
     /// something unique to this crate (e.g., a module path) as well
     /// as the crate name and disambiguator.
+    /// We currently generate these names via CodegenUnit::build_cgu_name().
     name: String,
-    llmod_id: String,
     source: ModuleSource,
     kind: ModuleKind,
 }
@@ -317,7 +317,6 @@ impl ModuleCodegen {
         };
 
         CompiledModule {
-            llmod_id: self.llmod_id,
             name: self.name.clone(),
             kind: self.kind,
             pre_existing,
@@ -331,7 +330,6 @@ impl ModuleCodegen {
 #[derive(Debug)]
 struct CompiledModule {
     name: String,
-    llmod_id: String,
     kind: ModuleKind,
     pre_existing: bool,
     object: Option<PathBuf>,