Support local ThinLTO with incremental compilation.

src/librustc_codegen_llvm/lib.rs

@@ -66,13 +66,13 @@ extern crate rustc_errors as errors;
 extern crate serialize;
 extern crate cc; // Used to locate MSVC
 extern crate tempfile;
+extern crate memmap;
 
 use back::bytecode::RLIB_BYTECODE_EXTENSION;
 
 pub use llvm_util::target_features;
-
 use std::any::Any;
-use std::path::PathBuf;
+use std::path::{PathBuf};
 use std::sync::mpsc;
 use rustc_data_structures::sync::Lrc;
 
@@ -273,10 +273,15 @@ struct ModuleCodegen {
     /// as the crate name and disambiguator.
     /// We currently generate these names via CodegenUnit::build_cgu_name().
     name: String,
-    source: ModuleSource,
+    module_llvm: ModuleLlvm,
     kind: ModuleKind,
 }
 
+struct CachedModuleCodegen {
+    name: String,
+    source: WorkProduct,
+}
+
 #[derive(Copy, Clone, Debug, PartialEq)]
 enum ModuleKind {
     Regular,
@@ -285,22 +290,11 @@ enum ModuleKind {
 }
 
 impl ModuleCodegen {
-    fn llvm(&self) -> Option<&ModuleLlvm> {
-        match self.source {
-            ModuleSource::Codegened(ref llvm) => Some(llvm),
-            ModuleSource::Preexisting(_) => None,
-        }
-    }
-
     fn into_compiled_module(self,
-                                emit_obj: bool,
-                                emit_bc: bool,
-                                emit_bc_compressed: bool,
-                                outputs: &OutputFilenames) -> CompiledModule {
-        let pre_existing = match self.source {
-            ModuleSource::Preexisting(_) => true,
-            ModuleSource::Codegened(_) => false,
-        };
+                            emit_obj: bool,
+                            emit_bc: bool,
+                            emit_bc_compressed: bool,
+                            outputs: &OutputFilenames) -> CompiledModule {
         let object = if emit_obj {
             Some(outputs.temp_path(OutputType::Object, Some(&self.name)))
         } else {
@@ -321,7 +315,6 @@ impl ModuleCodegen {
         CompiledModule {
             name: self.name.clone(),
             kind: self.kind,
-            pre_existing,
             object,
             bytecode,
             bytecode_compressed,
@@ -333,20 +326,11 @@ impl ModuleCodegen {
 struct CompiledModule {
     name: String,
     kind: ModuleKind,
-    pre_existing: bool,
     object: Option<PathBuf>,
     bytecode: Option<PathBuf>,
     bytecode_compressed: Option<PathBuf>,
 }
 
-enum ModuleSource {
-    /// Copy the `.o` files or whatever from the incr. comp. directory.
-    Preexisting(WorkProduct),
-
-    /// Rebuild from this LLVM module.
-    Codegened(ModuleLlvm),
-}
-
 struct ModuleLlvm {
     llcx: &'static mut llvm::Context,
     llmod_raw: *const llvm::Module,