llvm: update ffi bindings for split dwarf

This commit modifies the FFI bindings to LLVM required for Split DWARF
support in rustc. In particular:

- `addPassesToEmitFile`'s wrapper, `LLVMRustWriteOutputFile` now takes
  a `DwoPath` `const char*`. When disabled, `nullptr` should be provided
  which will preserve existing behaviour. When enabled, the path to the
  `.dwo` file should be provided.
- `createCompileUnit`'s wrapper, `LLVMRustDIBuilderCreateCompileUnit`
  now has two additional arguments, for the `DWOId` and to enable
  `SplitDebugInlining`. `DWOId` should always be zero.
- `createTargetMachine`'s wrapper, `LLVMRustCreateTargetMachine` has an
  additional argument which should be provided the path to the `.dwo`
  when enabled.

Signed-off-by: David Wood <david@davidtw.co>

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -53,7 +53,14 @@ pub fn write_output_file(
 ) -> Result<(), FatalError> {
     unsafe {
         let output_c = path_to_c_string(output);
-        let result = llvm::LLVMRustWriteOutputFile(target, pm, m, output_c.as_ptr(), file_type);
+        let result = llvm::LLVMRustWriteOutputFile(
+            target,
+            pm,
+            m,
+            output_c.as_ptr(),
+            std::ptr::null(),
+            file_type,
+        );
         result.into_result().map_err(|()| {
             let msg = format!("could not write output to {}", output.display());
             llvm_err(handler, &msg)
@@ -164,6 +171,7 @@ pub fn target_machine_factory(
         !sess.opts.debugging_opts.use_ctors_section.unwrap_or(sess.target.use_ctors_section);
 
     Arc::new(move || {
+        let split_dwarf_file = std::ptr::null();
         let tm = unsafe {
             llvm::LLVMRustCreateTargetMachine(
                 triple.as_ptr(),
@@ -182,6 +190,7 @@ pub fn target_machine_factory(
                 emit_stack_size_section,
                 relax_elf_relocations,
                 use_init_array,
+                split_dwarf_file,
             )
         };
 

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -1039,6 +1039,8 @@ pub fn compile_unit_metadata(
             split_name.as_ptr().cast(),
             split_name.len(),
             kind,
+            0,
+            true,
         );
 
         if tcx.sess.opts.debugging_opts.profile {

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1830,6 +1830,8 @@ extern "C" {
         SplitName: *const c_char,
         SplitNameLen: size_t,
         kind: DebugEmissionKind,
+        DWOId: u64,
+        SplitDebugInlining: bool,
     ) -> &'a DIDescriptor;
 
     pub fn LLVMRustDIBuilderCreateFile(
@@ -2151,6 +2153,7 @@ extern "C" {
         EmitStackSizeSection: bool,
         RelaxELFRelocations: bool,
         UseInitArray: bool,
+        SplitDwarfFile: *const c_char,
     ) -> Option<&'static mut TargetMachine>;
     pub fn LLVMRustDisposeTargetMachine(T: &'static mut TargetMachine);
     pub fn LLVMRustAddBuilderLibraryInfo(
@@ -2179,6 +2182,7 @@ extern "C" {
         PM: &PassManager<'a>,
         M: &'a Module,
         Output: *const c_char,
+        DwoOutput: *const c_char,
         FileType: FileType,
     ) -> LLVMRustResult;
     pub fn LLVMRustOptimizeWithNewPassManager(

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -450,7 +450,8 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
     bool AsmComments,
     bool EmitStackSizeSection,
     bool RelaxELFRelocations,
-    bool UseInitArray) {
+    bool UseInitArray,
+    const char *SplitDwarfFile) {
 
   auto OptLevel = fromRust(RustOptLevel);
   auto RM = fromRust(RustReloc);
@@ -476,6 +477,9 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
   Options.MCOptions.AsmVerbose = AsmComments;
   Options.MCOptions.PreserveAsmComments = AsmComments;
   Options.MCOptions.ABIName = ABIStr;
+  if (SplitDwarfFile) {
+      Options.MCOptions.SplitDwarfFile = SplitDwarfFile;
+  }
   Options.RelaxELFRelocations = RelaxELFRelocations;
   Options.UseInitArray = UseInitArray;
 
@@ -610,7 +614,7 @@ static TargetMachine::CodeGenFileType fromRust(LLVMRustFileType Type) {
 
 extern "C" LLVMRustResult
 LLVMRustWriteOutputFile(LLVMTargetMachineRef Target, LLVMPassManagerRef PMR,
-                        LLVMModuleRef M, const char *Path,
+                        LLVMModuleRef M, const char *Path, const char *DwoPath,
                         LLVMRustFileType RustFileType) {
   llvm::legacy::PassManager *PM = unwrap<llvm::legacy::PassManager>(PMR);
   auto FileType = fromRust(RustFileType);
@@ -626,8 +630,22 @@ LLVMRustWriteOutputFile(LLVMTargetMachineRef Target, LLVMPassManagerRef PMR,
   }
 
   buffer_ostream BOS(OS);
-  unwrap(Target)->addPassesToEmitFile(*PM, BOS, nullptr, FileType, false);
-  PM->run(*unwrap(M));
+  if (DwoPath) {
+    raw_fd_ostream DOS(DwoPath, EC, sys::fs::F_None);
+    EC.clear();
+    if (EC)
+        ErrorInfo = EC.message();
+    if (ErrorInfo != "") {
+      LLVMRustSetLastError(ErrorInfo.c_str());
+      return LLVMRustResult::Failure;
+    }
+    buffer_ostream DBOS(DOS);
+    unwrap(Target)->addPassesToEmitFile(*PM, BOS, &DBOS, FileType, false);
+    PM->run(*unwrap(M));
+  } else {
+    unwrap(Target)->addPassesToEmitFile(*PM, BOS, nullptr, FileType, false);
+    PM->run(*unwrap(M));
+  }
 
   // Apparently `addPassesToEmitFile` adds a pointer to our on-the-stack output
   // stream (OS), so the only real safe place to delete this is here? Don't we

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -690,13 +690,14 @@ extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateCompileUnit(
     const char *Producer, size_t ProducerLen, bool isOptimized,
     const char *Flags, unsigned RuntimeVer,
     const char *SplitName, size_t SplitNameLen,
-    LLVMRustDebugEmissionKind Kind) {
+    LLVMRustDebugEmissionKind Kind,
+    uint64_t DWOId, bool SplitDebugInlining) {
   auto *File = unwrapDI<DIFile>(FileRef);
 
   return wrap(Builder->createCompileUnit(Lang, File, StringRef(Producer, ProducerLen),
                                          isOptimized, Flags, RuntimeVer,
                                          StringRef(SplitName, SplitNameLen),
-                                         fromRust(Kind)));
+                                         fromRust(Kind), DWOId, SplitDebugInlining));
 }
 
 extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateFile(