rewrite DW_TAG_compile_unit during aotcompile (JuliaLang#49183)

The macOS linker requires these to be unique due to a bug, and we do not
care about this value at all as it does nothing, so just make it
something unique. However, keep the directory as ".", since it uses that
to compose the DW_AT_decl_file values for its subprograms.

Also try to save a little memory, since we have to leak all of these
objects (per LLVMContext), and we would like to avoid that.

Fix JuliaLang#49152
Fix JuliaLang#49151
Fix JuliaLang#49153

Author: vtjnash

src/aotcompile.cpp

@@ -1341,6 +1341,11 @@ static void add_output(Module &M, TargetMachine &TM, std::vector<std::string> &o
             timers[i].construct.startTimer();
             construct_vars(*M, partitions[i]);
             M->setModuleFlag(Module::Error, "julia.mv.suffix", MDString::get(M->getContext(), "_" + std::to_string(i)));
+            // The DICompileUnit file is not used for anything, but ld64 requires it be a unique string per object file
+            // or it may skip emitting debug info for that file. Here set it to ./julia#N
+            DIFile *topfile = DIFile::get(M->getContext(), "julia#" + std::to_string(i), ".");
+            for (DICompileUnit *CU : M->debug_compile_units())
+                CU->replaceOperandWith(0, topfile);
             timers[i].construct.stopTimer();
 
             timers[i].deletion.startTimer();

src/cgutils.cpp

@@ -153,6 +153,39 @@ Metadata *to_md_tree(jl_value_t *val, LLVMContext &ctxt) {
 
 // --- Debug info ---
 
+static DICompileUnit *getOrCreateJuliaCU(Module &M,
+    DICompileUnit::DebugEmissionKind emissionKind,
+    DICompileUnit::DebugNameTableKind tableKind)
+{
+    // TODO: share debug objects globally in the context, instead of allocating a new one every time
+    // or figure out how to delete them afterwards?
+    // But at least share them a little bit here
+    auto CUs = M.debug_compile_units();
+    for (DICompileUnit *CU : CUs) {
+        if (CU->getEmissionKind() == emissionKind &&
+            CU->getNameTableKind() == tableKind)
+        return CU;
+    }
+    DIFile *topfile = DIFile::get(M.getContext(), "julia", ".");
+    DIBuilder dbuilder(M);
+    DICompileUnit *CU =
+        dbuilder.createCompileUnit(llvm::dwarf::DW_LANG_Julia
+                                   ,topfile      // File
+                                   ,"julia"      // Producer
+                                   ,true         // isOptimized
+                                   ,""           // Flags
+                                   ,0            // RuntimeVersion
+                                   ,""           // SplitName
+                                   ,emissionKind // Kind
+                                   ,0            // DWOId
+                                   ,true         // SplitDebugInlining
+                                   ,false        // DebugInfoForProfiling
+                                   ,tableKind    // NameTableKind
+                                   );
+    dbuilder.finalize();
+    return CU;
+}
+
 static DIType *_julia_type_to_di(jl_codegen_params_t *ctx, jl_debugcache_t &debuginfo, jl_value_t *jt, DIBuilder *dbuilder, bool isboxed)
 {
     jl_datatype_t *jdt = (jl_datatype_t*)jt;

src/codegen.cpp

@@ -7149,47 +7149,26 @@ static jl_llvm_functions_t
     ctx.f = f;
 
     // Step 4b. determine debug info signature and other type info for locals
-    DIBuilder dbuilder(*M);
+    DICompileUnit::DebugEmissionKind emissionKind = (DICompileUnit::DebugEmissionKind) ctx.params->debug_info_kind;
+    DICompileUnit::DebugNameTableKind tableKind;
+    if (JL_FEAT_TEST(ctx, gnu_pubnames))
+        tableKind = DICompileUnit::DebugNameTableKind::GNU;
+    else
+        tableKind = DICompileUnit::DebugNameTableKind::None;
+    DIBuilder dbuilder(*M, true, ctx.debug_enabled ? getOrCreateJuliaCU(*M, emissionKind, tableKind) : NULL);
     DIFile *topfile = NULL;
     DISubprogram *SP = NULL;
     DebugLoc noDbg, topdebugloc;
     if (ctx.debug_enabled) {
-        DICompileUnit::DebugEmissionKind emissionKind = (DICompileUnit::DebugEmissionKind) ctx.params->debug_info_kind;
-        DICompileUnit::DebugNameTableKind tableKind;
-
-        if (JL_FEAT_TEST(ctx, gnu_pubnames)) {
-            tableKind = DICompileUnit::DebugNameTableKind::GNU;
-        }
-        else {
-            tableKind = DICompileUnit::DebugNameTableKind::None;
-        }
         topfile = dbuilder.createFile(ctx.file, ".");
-        DICompileUnit *CU =
-            dbuilder.createCompileUnit(llvm::dwarf::DW_LANG_Julia
-                                       ,topfile      // File
-                                       ,"julia"      // Producer
-                                       ,true         // isOptimized
-                                       ,""           // Flags
-                                       ,0            // RuntimeVersion
-                                       ,""           // SplitName
-                                       ,emissionKind // Kind
-                                       ,0            // DWOId
-                                       ,true         // SplitDebugInlining
-                                       ,false        // DebugInfoForProfiling
-                                       ,tableKind    // NameTableKind
-                                       );
-
         DISubroutineType *subrty;
-        if (jl_options.debug_level <= 1) {
+        if (jl_options.debug_level <= 1)
             subrty = debuginfo.jl_di_func_null_sig;
-        }
-        else if (!specsig) {
+        else if (!specsig)
             subrty = debuginfo.jl_di_func_sig;
-        }
-        else {
+        else
             subrty = get_specsig_di(ctx, debuginfo, jlrettype, lam->specTypes, dbuilder);
-        }
-        SP = dbuilder.createFunction(CU
+        SP = dbuilder.createFunction(nullptr
                                      ,dbgFuncName      // Name
                                      ,f->getName()     // LinkageName
                                      ,topfile          // File

src/jitlayers.cpp

@@ -1694,8 +1694,8 @@ void jl_merge_module(orc::ThreadSafeModule &destTSM, orc::ThreadSafeModule srcTS
             NamedMDNode *sNMD = src.getNamedMetadata("llvm.dbg.cu");
             if (sNMD) {
                 NamedMDNode *dNMD = dest.getOrInsertNamedMetadata("llvm.dbg.cu");
-                for (NamedMDNode::op_iterator I = sNMD->op_begin(), E = sNMD->op_end(); I != E; ++I) {
-                    dNMD->addOperand(*I);
+                for (MDNode *I : sNMD->operands()) {
+                    dNMD->addOperand(I);
                 }
             }
         });