[MS] Fix C++ destructor thunk line info for a declaration

Sometimes the MS ABI needs to emit thunks for declarations that don't
have bodies. Destructor thunks make calls to inlinable functions, so
they need line info or LLVM will complain.

Fixes PR31893

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@294465 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CodeGenFunction.cpp

@@ -1089,8 +1089,13 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn,
   if (FD->hasAttr<NoDebugAttr>())
     DebugInfo = nullptr; // disable debug info indefinitely for this function
 
+  // The function might not have a body if we're generating thunks for a
+  // function declaration.
   SourceRange BodyRange;
-  if (Stmt *Body = FD->getBody()) BodyRange = Body->getSourceRange();
+  if (Stmt *Body = FD->getBody())
+    BodyRange = Body->getSourceRange();
+  else
+    BodyRange = FD->getLocation();
   CurEHLocation = BodyRange.getEnd();
 
   // Use the location of the start of the function to determine where

test/CodeGenCXX/debug-info-ms-dtor-thunks.cpp

@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple i686--windows -emit-llvm -debug-info-kind=line-tables-only -x c++ %s -fms-extensions -o - | FileCheck %s
+
+struct __declspec(dllexport) S { virtual ~S(); };
+struct __declspec(dllexport) T { virtual ~T(); };
+struct __declspec(dllexport) U : S, T { virtual ~U(); };
+
+// CHECK-LABEL: define {{.*}} @"\01??_GS@@UAEPAXI@Z"
+// CHECK: call x86_thiscallcc void @"\01??_DS@@UAE@XZ"(%struct.S* %this1){{.*}}!dbg !{{[0-9]+}}
+
+// CHECK-LABEL: define {{.*}} @"\01??_GT@@UAEPAXI@Z"
+// CHECK: call x86_thiscallcc void @"\01??_DT@@UAE@XZ"(%struct.T* %this1){{.*}}!dbg !{{[0-9]+}}
+
+// CHECK-LABEL: define {{.*}} @"\01??_GU@@UAEPAXI@Z"
+// CHECK: call x86_thiscallcc void @"\01??_DU@@UAE@XZ"(%struct.U* %this1){{.*}}!dbg !{{[0-9]+}}