[RemoveDIs] Update Clang front end to handle DbgRecords (#84756)

This patch fixes problems that pop up when clang emits DbgRecords
instead of debug intrinsics.

Note: this doesn't mean clang is emitting DbgRecords yet, because the
modules it creates are still always in the old debug mode. That will
come in a future patch.

Depends on #84739

Author: OCHyams

clang/lib/CodeGen/CGBlocks.cpp

@@ -1540,7 +1540,10 @@ llvm::Function *CodeGenFunction::GenerateBlockFunction(
   llvm::BasicBlock *resume = Builder.GetInsertBlock();
 
   // Go back to the entry.
-  ++entry_ptr;
+  if (entry_ptr->getNextNonDebugInstruction())
+    entry_ptr = entry_ptr->getNextNonDebugInstruction()->getIterator();
+  else
+    entry_ptr = entry->end();
   Builder.SetInsertPoint(entry, entry_ptr);
 
   // Emit debug information for all the DeclRefExprs.

clang/lib/CodeGen/CGStmtOpenMP.cpp

@@ -4749,20 +4749,32 @@ void CodeGenFunction::EmitOMPTaskBasedDirective(
           if (CGF.CGM.getCodeGenOpts().hasReducedDebugInfo())
             (void)DI->EmitDeclareOfAutoVariable(SharedVar, ContextValue,
                                                 CGF.Builder, false);
-          llvm::Instruction &Last = CGF.Builder.GetInsertBlock()->back();
           // Get the call dbg.declare instruction we just created and update
           // its DIExpression to add offset to base address.
-          if (auto DDI = dyn_cast<llvm::DbgVariableIntrinsic>(&Last)) {
+          auto UpdateExpr = [](llvm::LLVMContext &Ctx, auto *Declare,
+                               unsigned Offset) {
             SmallVector<uint64_t, 8> Ops;
             // Add offset to the base address if non zero.
             if (Offset) {
               Ops.push_back(llvm::dwarf::DW_OP_plus_uconst);
               Ops.push_back(Offset);
             }
             Ops.push_back(llvm::dwarf::DW_OP_deref);
-            auto &Ctx = DDI->getContext();
-            llvm::DIExpression *DIExpr = llvm::DIExpression::get(Ctx, Ops);
-            Last.setOperand(2, llvm::MetadataAsValue::get(Ctx, DIExpr));
+            Declare->setExpression(llvm::DIExpression::get(Ctx, Ops));
+          };
+          llvm::Instruction &Last = CGF.Builder.GetInsertBlock()->back();
+          if (auto DDI = dyn_cast<llvm::DbgVariableIntrinsic>(&Last))
+            UpdateExpr(DDI->getContext(), DDI, Offset);
+          // If we're emitting using the new debug info format into a block
+          // without a terminator, the record will be "trailing".
+          assert(!Last.isTerminator() && "unexpected terminator");
+          if (auto *Marker =
+                  CGF.Builder.GetInsertBlock()->getTrailingDbgRecords()) {
+            for (llvm::DPValue &DPV : llvm::reverse(
+                     llvm::filterDbgVars(Marker->getDbgRecordRange()))) {
+              UpdateExpr(Last.getContext(), &DPV, Offset);
+              break;
+            }
           }
         }
       }

clang/test/CodeGenObjC/debug-info-blocks.m

@@ -5,8 +5,8 @@
 
 // CHECK: define {{.*}}_block_invoke
 // CHECK: store ptr %.block_descriptor, ptr %[[ALLOCA:block.addr]], align
-// CHECK-NEXT: call void @llvm.dbg.declare(metadata ptr %[[ALLOCA]], metadata ![[SELF:[0-9]+]], metadata !{{.*}})
 // CHECK-NEXT: call void @llvm.dbg.declare(metadata ptr %d, metadata ![[D:[0-9]+]], metadata !{{.*}})
+// CHECK-NEXT: call void @llvm.dbg.declare(metadata ptr %[[ALLOCA]], metadata ![[SELF:[0-9]+]], metadata !{{.*}})
 
 // Test that we do emit scope info for the helper functions, and that the
 // parameters to these functions are marked as artificial (so the debugger