[ubsan] Have -fsanitize=vptr emit a null check if -fsanitize=null isn't available

In r309007, I made -fsanitize=null a hard prerequisite for -fsanitize=vptr. I
did not see the need for the two checks to have separate null checking logic
for the same pointer. I expected the two checks to either always be enabled
together, or to be mutually compatible.

In the mailing list discussion re: r309007 it became clear that that isn't the
case. If a codebase is -fsanitize=vptr clean but not -fsanitize=null clean,
it's useful to have -fsanitize=vptr emit its own null check. That's what this
patch does: with it, -fsanitize=vptr can be used without -fsanitize=null.

Differential Revision: https://reviews.llvm.org/D36112

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@309846 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 5 deletions

diff --git a/test/CodeGenCXX/ubsan-type-checks.cpp b/test/CodeGenCXX/ubsan-type-checks.cpp
index cc2d4d6e79..e53ab2466e 100644
--- a/test/CodeGenCXX/ubsan-type-checks.cpp
+++ b/test/CodeGenCXX/ubsan-type-checks.cpp
@@ -44,17 +44,22 @@ struct Dog : Animal {
 
 // VPTR-LABEL: define void @_Z12invalid_castP3Cat
 void invalid_cast(Cat *cat = nullptr) {
-  // First, null check the pointer:
+  // If -fsanitize=null is available, we'll reuse its check:
   //
   // VPTR: [[ICMP:%.*]] = icmp ne %struct.Dog* {{.*}}, null
   // VPTR-NEXT: br i1 [[ICMP]]
   // VPTR: call void @__ubsan_handle_type_mismatch
-  //
-  // Once we're done emitting the null check, reuse the check to see if we can
-  // proceed to the vptr check:
-  //
+  // VPTR-NOT: icmp ne %struct.Dog* {{.*}}, null
   // VPTR: br i1 [[ICMP]]
   // VPTR: call void @__ubsan_handle_dynamic_type_cache_miss
+  //
+  // Fall back to the vptr sanitizer's null check when -fsanitize=null isn't
+  // available.
+  //
+  // VPTR_NO_NULL-NOT: call void @__ubsan_handle_type_mismatch
+  // VPTR_NO_NULL: [[ICMP:%.*]] = icmp ne %struct.Dog* {{.*}}, null
+  // VPTR_NO_NULL-NEXT: br i1 [[ICMP]]
+  // VPTR_NO_NULL: call void @__ubsan_handle_dynamic_type_cache_miss
   auto *badDog = reinterpret_cast<Dog *>(cat);
   badDog->speak();
 }