Work around debug_compile_units skipping nodebug CUs (#59649)

Author: gbaraldi

src/aotcompile.cpp

@@ -1957,8 +1957,9 @@ static SmallVector<AOTOutputs, 16> add_output(Module &M, TargetMachine &TM, Stri
                 // 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);
+                if (M->getNamedMetadata("llvm.dbg.cu"))
+                    for (auto CU: M->getNamedMetadata("llvm.dbg.cu")->operands())
+                        CU->replaceOperandWith(0, topfile);
                 timers[i].construct.stopTimer();
 
                 outputs[i] = add_output_impl(*M, TM, timers[i], unopt_out, opt_out, obj_out, asm_out);

src/llvm-multiversioning.cpp

@@ -487,8 +487,9 @@ void CloneCtx::prepare_vmap(ValueToValueMapTy &vmap)
     // The `DISubprogram` cloning on LLVM 5.0 handles this
     // but it doesn't hurt to enforce the identity either.
     auto &MD = vmap.MD();
-    for (auto cu: M.debug_compile_units()) {
-        MD[cu].reset(cu);
+    if (M.getNamedMetadata("llvm.dbg.cu"))
+        for (auto cu: M.getNamedMetadata("llvm.dbg.cu")->operands()) {
+            MD[cu].reset(cu);
     }
 }
 

src/llvm-remove-addrspaces.cpp

@@ -336,9 +336,10 @@ bool removeAddrspaces(Module &M, AddrspaceRemapFunction ASRemapper)
     }
     // Same workaround as in CloneCtx::prepare_vmap to avoid LLVM bug when cloning
     auto &MD = VMap.MD();
-    for (auto cu: M.debug_compile_units()) {
-        MD[cu].reset(cu);
-    }
+    if (M.getNamedMetadata("llvm.dbg.cu"))
+        for (auto cu: M.getNamedMetadata("llvm.dbg.cu")->operands()) {
+            MD[cu].reset(cu);
+        }
     // Similarly, copy over and rewrite function bodies
     for (Function *F : Functions) {
         Function *NF = cast<Function>(VMap[F]);