Fix PR35902: incorrect alignment used for ubsan check.

UBSan was using the complete-object align rather than nv alignment
when checking the "this" pointer of a method.

Furthermore, CGF.CXXABIThisAlignment was also being set incorrectly,
due to an incorrectly negated test. The latter doesn't appear to have
had any impact, due to it not really being used anywhere.

Differential Revision: https://reviews.llvm.org/D93072

clang/lib/CodeGen/CGCXXABI.cpp

@@ -135,8 +135,8 @@ void CGCXXABI::buildThisParam(CodeGenFunction &CGF, FunctionArgList &params) {
   // down to whether we know it's a complete object or not.
   auto &Layout = CGF.getContext().getASTRecordLayout(MD->getParent());
   if (MD->getParent()->getNumVBases() == 0 || // avoid vcall in common case
-      MD->getParent()->hasAttr<FinalAttr>() ||
-      !isThisCompleteObject(CGF.CurGD)) {
+      MD->getParent()->isEffectivelyFinal() ||
+      isThisCompleteObject(CGF.CurGD)) {
     CGF.CXXABIThisAlignment = Layout.getAlignment();
   } else {
     CGF.CXXABIThisAlignment = Layout.getNonVirtualAlignment();

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -1137,11 +1137,9 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
           MD->getParent()->getLambdaCaptureDefault() == LCD_None)
         SkippedChecks.set(SanitizerKind::Null, true);
 
-      EmitTypeCheck(isa<CXXConstructorDecl>(MD) ? TCK_ConstructorCall
-                                                : TCK_MemberCall,
-                    Loc, CXXABIThisValue, ThisTy,
-                    getContext().getTypeAlignInChars(ThisTy->getPointeeType()),
-                    SkippedChecks);
+      EmitTypeCheck(
+          isa<CXXConstructorDecl>(MD) ? TCK_ConstructorCall : TCK_MemberCall,
+          Loc, CXXABIThisValue, ThisTy, CXXABIThisAlignment, SkippedChecks);
     }
   }
 

clang/test/CodeGenCXX/catch-undef-behavior.cpp

@@ -430,8 +430,8 @@ namespace VBaseObjectSize {
   // Note: C is laid out such that offsetof(C, B) + sizeof(B) extends outside
   // the C object.
   struct alignas(16) A { void *a1, *a2; };
-  struct B : virtual A { void *b; };
-  struct C : virtual A, virtual B {};
+  struct B : virtual A { void *b; void* g(); };
+  struct C : virtual A, virtual B { };
   // CHECK-LABEL: define {{.*}} @_ZN15VBaseObjectSize1fERNS_1BE(
   B &f(B &b) {
     // Size check: check for nvsize(B) == 16 (do not require size(B) == 32)
@@ -443,6 +443,15 @@ namespace VBaseObjectSize {
     // CHECK: and i64 [[PTRTOINT]], 7,
     return b;
   }
+
+  // CHECK-LABEL: define {{.*}} @_ZN15VBaseObjectSize1B1gEv(
+  void *B::g() {
+    // Ensure that the check on the "this" pointer also uses the proper
+    // alignment. We should be using nvalign(B) == 8, not 16.
+    // CHECK: [[PTRTOINT:%.+]] = ptrtoint {{.*}} to i64,
+    // CHECK: and i64 [[PTRTOINT]], 7
+    return nullptr;
+  }
 }
 
 namespace FunctionSanitizerVirtualCalls {