Auto merge of #84171 - ricobbe:raw-dylib-via-llvm, r=petrochenkov

Partial support for raw-dylib linkage

First cut of functionality for issue #58713: add support for `#[link(kind = "raw-dylib")]` on `extern` blocks in lib crates compiled to .rlib files.  Does not yet support `#[link_name]` attributes on functions, or the `#[link_ordinal]` attribute, or `#[link(kind = "raw-dylib")]` on `extern` blocks in bin crates; I intend to publish subsequent PRs to fill those gaps.  It's also not yet clear whether this works for functions in `extern "stdcall"` blocks; I also intend to investigate that shortly and make any necessary changes as a follow-on PR.

This implementation calls out to an LLVM function to construct the actual `.idata` sections as temporary `.lib` files on disk and then links those into the generated .rlib.

2 files changed, 116 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_llvm/src/back/archive.rs b/compiler/rustc_codegen_llvm/src/back/archive.rs
index 261affe2c42..64416bced31 100644
--- a/compiler/rustc_codegen_llvm/src/back/archive.rs
+++ b/compiler/rustc_codegen_llvm/src/back/archive.rs
@@ -8,9 +8,11 @@ use std::ptr;
 use std::str;
 
 use crate::llvm::archive_ro::{ArchiveRO, Child};
-use crate::llvm::{self, ArchiveKind};
+use crate::llvm::{self, ArchiveKind, LLVMMachineType, LLVMRustCOFFShortExport};
 use rustc_codegen_ssa::back::archive::{find_library, ArchiveBuilder};
 use rustc_codegen_ssa::{looks_like_rust_object_file, METADATA_FILENAME};
+use rustc_data_structures::temp_dir::MaybeTempDir;
+use rustc_middle::middle::cstore::DllImport;
 use rustc_session::Session;
 use rustc_span::symbol::Symbol;
 
@@ -61,6 +63,17 @@ fn archive_config<'a>(sess: &'a Session, output: &Path, input: Option<&Path>) ->
     }
 }
 
+/// Map machine type strings to values of LLVM's MachineTypes enum.
+fn llvm_machine_type(cpu: &str) -> LLVMMachineType {
+    match cpu {
+        "x86_64" => LLVMMachineType::AMD64,
+        "x86" => LLVMMachineType::I386,
+        "aarch64" => LLVMMachineType::ARM64,
+        "arm" => LLVMMachineType::ARM,
+        _ => panic!("unsupported cpu type {}", cpu),
+    }
+}
+
 impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
     /// Creates a new static archive, ready for modifying the archive specified
     /// by `config`.
@@ -175,6 +188,74 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
             self.config.sess.fatal(&format!("failed to build archive: {}", e));
         }
     }
+
+    fn inject_dll_import_lib(
+        &mut self,
+        lib_name: &str,
+        dll_imports: &[DllImport],
+        tmpdir: &MaybeTempDir,
+    ) {
+        let output_path = {
+            let mut output_path: PathBuf = tmpdir.as_ref().to_path_buf();
+            output_path.push(format!("{}_imports", lib_name));
+            output_path.with_extension("lib")
+        };
+
+        // we've checked for \0 characters in the library name already
+        let dll_name_z = CString::new(lib_name).unwrap();
+        // All import names are Rust identifiers and therefore cannot contain \0 characters.
+        // FIXME: when support for #[link_name] implemented, ensure that import.name values don't
+        // have any \0 characters
+        let import_name_vector: Vec<CString> = dll_imports
+            .iter()
+            .map(if self.config.sess.target.arch == "x86" {
+                |import: &DllImport| CString::new(format!("_{}", import.name.to_string())).unwrap()
+            } else {
+                |import: &DllImport| CString::new(import.name.to_string()).unwrap()
+            })
+            .collect();
+
+        let output_path_z = rustc_fs_util::path_to_c_string(&output_path);
+
+        tracing::trace!("invoking LLVMRustWriteImportLibrary");
+        tracing::trace!("  dll_name {:#?}", dll_name_z);
+        tracing::trace!("  output_path {}", output_path.display());
+        tracing::trace!(
+            "  import names: {}",
+            dll_imports.iter().map(|import| import.name.to_string()).collect::<Vec<_>>().join(", "),
+        );
+
+        let ffi_exports: Vec<LLVMRustCOFFShortExport> = import_name_vector
+            .iter()
+            .map(|name_z| LLVMRustCOFFShortExport::from_name(name_z.as_ptr()))
+            .collect();
+        let result = unsafe {
+            crate::llvm::LLVMRustWriteImportLibrary(
+                dll_name_z.as_ptr(),
+                output_path_z.as_ptr(),
+                ffi_exports.as_ptr(),
+                ffi_exports.len(),
+                llvm_machine_type(&self.config.sess.target.arch) as u16,
+                !self.config.sess.target.is_like_msvc,
+            )
+        };
+
+        if result == crate::llvm::LLVMRustResult::Failure {
+            self.config.sess.fatal(&format!(
+                "Error creating import library for {}: {}",
+                lib_name,
+                llvm::last_error().unwrap_or("unknown LLVM error".to_string())
+            ));
+        }
+
+        self.add_archive(&output_path, |_| false).unwrap_or_else(|e| {
+            self.config.sess.fatal(&format!(
+                "failed to add native library {}: {}",
+                output_path.display(),
+                e
+            ));
+        });
+    }
 }
 
 impl<'a> LlvmArchiveBuilder<'a> {
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 115aa74dcc4..91923251018 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -29,6 +29,31 @@ pub enum LLVMRustResult {
     Success,
     Failure,
 }
+
+// Rust version of the C struct with the same name in rustc_llvm/llvm-wrapper/RustWrapper.cpp.
+#[repr(C)]
+pub struct LLVMRustCOFFShortExport {
+    pub name: *const c_char,
+}
+
+impl LLVMRustCOFFShortExport {
+    pub fn from_name(name: *const c_char) -> LLVMRustCOFFShortExport {
+        LLVMRustCOFFShortExport { name }
+    }
+}
+
+/// Translation of LLVM's MachineTypes enum, defined in llvm\include\llvm\BinaryFormat\COFF.h.
+///
+/// We include only architectures supported on Windows.
+#[derive(Copy, Clone, PartialEq)]
+#[repr(C)]
+pub enum LLVMMachineType {
+    AMD64 = 0x8664,
+    I386 = 0x14c,
+    ARM64 = 0xaa64,
+    ARM = 0x01c0,
+}
+
 // Consts for the LLVM CallConv type, pre-cast to usize.
 
 /// LLVM CallingConv::ID. Should we wrap this?
@@ -2265,6 +2290,15 @@ extern "C" {
     ) -> &'a mut RustArchiveMember<'a>;
     pub fn LLVMRustArchiveMemberFree(Member: &'a mut RustArchiveMember<'a>);
 
+    pub fn LLVMRustWriteImportLibrary(
+        ImportName: *const c_char,
+        Path: *const c_char,
+        Exports: *const LLVMRustCOFFShortExport,
+        NumExports: usize,
+        Machine: u16,
+        MinGW: bool,
+    ) -> LLVMRustResult;
+
     pub fn LLVMRustSetDataLayoutFromTargetMachine(M: &'a Module, TM: &'a TargetMachine);
 
     pub fn LLVMRustBuildOperandBundleDef(