Fix logic for generating llvm.type.test()s

[vlad.tsyrklevich]

Summary

CodeGenFunction::EmitTypeMetadataCodeForVCall() could output an llvm.assume(llvm.type.test())when CFI was enabled, optimizing out the vcall check. This case was only reached when: 1) CFI-vcall was enabled, 2) -fwhole-program-tables was specified, and 3) -fno-sanitize-trap=cfi-vcall was specified.

This change is blocked on D36012 as it uncovers that bug.

[pcc]

LGTM

test/CodeGenCXX/cfi-vcall-no-trap.cpp

3

I don't think you need the -cc1 here, it should be implied by %clang_cc1.

11

I'd also test for presence of llvm.type.test to make sure that we're following the non-trapping CFI code path.

lib/CodeGen/CGClass.cpp

LeastDerivedClassWithSameLayout(const CXXRecordDecl *RD) {
 
   return LeastDerivedClassWithSameLayout(
       RD->bases_begin()->getType()->getAsCXXRecordDecl());
 }
 
 void CodeGenFunction::EmitTypeMetadataCodeForVCall(const CXXRecordDecl *RD,
                                                    llvm::Value *VTable,
                                                    SourceLocation Loc) {
-  if (CGM.getCodeGenOpts().WholeProgramVTables &&
+  if (SanOpts.has(SanitizerKind::CFIVCall))
+    EmitVTablePtrCheckForCall(RD, VTable, CodeGenFunction::CFITCK_VCall, Loc);
+  else if (CGM.getCodeGenOpts().WholeProgramVTables &&
            CGM.HasHiddenLTOVisibility(RD)) {
     llvm::Metadata *MD =
         CGM.CreateMetadataIdentifierForType(QualType(RD->getTypeForDecl(), 0));
     llvm::Value *TypeId =
         llvm::MetadataAsValue::get(CGM.getLLVMContext(), MD);
 
     llvm::Value *CastedVTable = Builder.CreateBitCast(VTable, Int8PtrTy);
     llvm::Value *TypeTest =
         Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::type_test),
                            {CastedVTable, TypeId});
     Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::assume), TypeTest);
   }
-
-  if (SanOpts.has(SanitizerKind::CFIVCall))
-    EmitVTablePtrCheckForCall(RD, VTable, CodeGenFunction::CFITCK_VCall, Loc);
 }
 
 void CodeGenFunction::EmitVTablePtrCheckForCall(const CXXRecordDecl *RD,
                                                 llvm::Value *VTable,
                                                 CFITypeCheckKind TCK,
                                                 SourceLocation Loc) {
   if (!SanOpts.has(SanitizerKind::CFICastStrict))
     RD = LeastDerivedClassWithSameLayout(RD);

test/CodeGenCXX/cfi-vcall-no-trap.cpp

+// Only output llvm.assume(llvm.type.test()) if cfi-vcall is disabled and whole-program-vtables is enabled
+// RUN: %clang_cc1 -fvisibility hidden -fsanitize=cfi-vcall -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=CFI %s
+// RUN: %clang_cc1 -fvisibility hidden -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=NOCFI %s
+
+struct S1 {
+  virtual void f();
+};
+
+// CHECK: define{{.*}}s1f
+// CHECK: llvm.type.test
+// CFI-NOT: llvm.assume
+// NOCFI: llvm.assume
+void s1f(S1 *s1) {
+  s1->f();
+}