Rollup merge of rust-lang#74787 - petrochenkov:rustllvm, r=cuviper

Move `rustllvm` into `compiler/rustc_llvm`

The `rustllvm` directory is not self-contained, it contains C++ code built by a build script of the `rustc_llvm` crate which is then linked into that crate.
So it makes sense to make `rustllvm` a part of `rustc_llvm` and move it into its directory.
I replaced `rustllvm` with more obvious `llvm-wrapper` as the subdirectory name, but something like `llvm-adapter` would work as well, other suggestions are welcome.

To make things more confusing, the Rust side of FFI functions defined in `rustllvm` can be found in `rustc_codegen_llvm` rather than in `rustc_llvm`. Perhaps they need to be moved as well, but this PR doesn't do that.

The presence of multiple LLVM-related directories in `src` (`llvm-project`, `rustllvm`, `librustc_llvm`, `librustc_codegen_llvm` and their predecessors) historically confused me and made me wonder about their purpose.
With this PR we will have LLVM itself (`llvm-project`), a FFI crate (`rustc_llvm`, kind of `llvm-sys`) and a codegen backend crate using LLVM through the FFI crate (`rustc_codegen_llvm`).

Author: tmandry

.gitignore

@@ -33,7 +33,6 @@ __pycache__/
 /mingw-build/
 # Created by default with `src/ci/docker/run.sh`:
 /obj/
-/rustllvm/
 /unicode-downloads
 /target
 # Generated by compiletest for incremental:

compiler/rustc_codegen_llvm/Cargo.toml

@@ -25,7 +25,7 @@ rustc_fs_util = { path = "../rustc_fs_util" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_incremental = { path = "../rustc_incremental" }
 rustc_index = { path = "../rustc_index" }
-rustc_llvm = { path = "../../src/librustc_llvm" }
+rustc_llvm = { path = "../rustc_llvm" }
 rustc_session = { path = "../rustc_session" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_target = { path = "../rustc_target" }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -96,7 +96,7 @@ pub enum DLLStorageClass {
     DllExport = 2, // Function to be accessible from DLL.
 }
 
-/// Matches LLVMRustAttribute in rustllvm.h
+/// Matches LLVMRustAttribute in LLVMWrapper.h
 /// Semantically a subset of the C++ enum llvm::Attribute::AttrKind,
 /// though it is not ABI compatible (since it's a C++ enum)
 #[repr(C)]
@@ -1705,7 +1705,7 @@ extern "C" {
         PM: &PassManager<'_>,
     );
 
-    // Stuff that's in rustllvm/ because it's not upstream yet.
+    // Stuff that's in llvm-wrapper/ because it's not upstream yet.
 
     /// Opens an object file.
     pub fn LLVMCreateObjectFile(

src/librustc_llvm/Cargo.toml renamed to compiler/rustc_llvm/Cargo.toml

@@ -4,9 +4,6 @@ name = "rustc_llvm"
 version = "0.0.0"
 edition = "2018"
 
-[lib]
-path = "lib.rs"
-
 [features]
 static-libstdcpp = []
 emscripten = []
@@ -15,5 +12,5 @@ emscripten = []
 libc = "0.2.73"
 
 [build-dependencies]
-build_helper = { path = "../build_helper" }
+build_helper = { path = "../../src/build_helper" }
 cc = "1.0.58"

src/librustc_llvm/build.rs renamed to compiler/rustc_llvm/build.rs

@@ -175,15 +175,15 @@ fn main() {
         cfg.debug(false);
     }
 
-    build_helper::rerun_if_changed_anything_in_dir(Path::new("../rustllvm"));
-    cfg.file("../rustllvm/PassWrapper.cpp")
-        .file("../rustllvm/RustWrapper.cpp")
-        .file("../rustllvm/ArchiveWrapper.cpp")
-        .file("../rustllvm/CoverageMappingWrapper.cpp")
-        .file("../rustllvm/Linker.cpp")
+    build_helper::rerun_if_changed_anything_in_dir(Path::new("llvm-wrapper"));
+    cfg.file("llvm-wrapper/PassWrapper.cpp")
+        .file("llvm-wrapper/RustWrapper.cpp")
+        .file("llvm-wrapper/ArchiveWrapper.cpp")
+        .file("llvm-wrapper/CoverageMappingWrapper.cpp")
+        .file("llvm-wrapper/Linker.cpp")
         .cpp(true)
         .cpp_link_stdlib(None) // we handle this below
-        .compile("rustllvm");
+        .compile("llvm-wrapper");
 
     let (llvm_kind, llvm_link_arg) = detect_llvm_link();
 
@@ -259,7 +259,7 @@ fn main() {
     }
 
     // Some LLVM linker flags (-L and -l) may be needed even when linking
-    // librustc_llvm, for example when using static libc++, we may need to
+    // rustc_llvm, for example when using static libc++, we may need to
     // manually specify the library search path and -ldl -lpthread as link
     // dependencies.
     let llvm_linker_flags = tracked_env_var_os("LLVM_LINKER_FLAGS");

src/rustllvm/.editorconfig renamed to compiler/rustc_llvm/llvm-wrapper/.editorconfig

@@ -1,4 +1,4 @@
-#include "rustllvm.h"
+#include "LLVMWrapper.h"
 
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/ArchiveWriter.h"

src/rustllvm/ArchiveWrapper.cpp renamed to compiler/rustc_llvm/llvm-wrapper/ArchiveWrapper.cpp

@@ -1,4 +1,4 @@
-#include "rustllvm.h"
+#include "LLVMWrapper.h"
 #include "llvm/ProfileData/Coverage/CoverageMapping.h"
 #include "llvm/ProfileData/Coverage/CoverageMappingWriter.h"
 #include "llvm/ProfileData/InstrProf.h"

src/rustllvm/CoverageMappingWrapper.cpp renamed to compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp

@@ -1,6 +1,6 @@
 #include "llvm/Linker/Linker.h"
 
-#include "rustllvm.h"
+#include "LLVMWrapper.h"
 
 using namespace llvm;