CodeGenTBAA/CGExpr: fix cases with may_alias arrays

Author: brunodf-snps

clang/lib/CodeGen/CGExpr.cpp

@@ -4524,11 +4524,8 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
       // If the array lvalue had no base type, there is no point trying to
       // generate one, since an array itself is not a valid base type.
 
-      // The access size must be updated to the size of an individual element.
-      // We also reset the access type using the original element type: in case
-      // of type decoration on the element type they may have been lost when
-      // the array type was canonicalized.
-      EltTBAAInfo.AccessType = CGM.getTBAATypeInfo(E->getType());
+      // We also retain the access type from the base lvalue, but the access
+      // size must be updated to the size of an individual element.
       EltTBAAInfo.Size =
           getContext().getTypeSizeInChars(E->getType()).getQuantity();
     }

clang/lib/CodeGen/CodeGenTBAA.cpp

@@ -130,6 +130,13 @@ static bool TypeHasMayAlias(QualType QTy) {
       return true;
     QTy = TT->desugar();
   }
+
+  // Also consider an array type as may_alias when its element type (at
+  // any level) is marked as such.
+  if (auto *ArrayTy = QTy->getAsArrayTypeUnsafe())
+    if (TypeHasMayAlias(ArrayTy->getElementType()))
+      return true;
+
   return false;
 }
 

clang/test/CodeGen/tbaa-array.cpp

@@ -13,6 +13,12 @@ struct C { int i; int x[3]; };
 struct D { int n; int arr[]; }; // flexible array member
 extern int AA[];                // incomplete array type
 
+typedef int __attribute__((may_alias)) aliasing_int;
+typedef int __attribute__((may_alias)) aliasing_array[10];
+struct E {
+    aliasing_int x[4]; aliasing_array y;
+};
+
 int foo(B *b) {
 // CHECK-LABEL: _Z3fooP1B
 // CHECK: load i32, {{.*}}, !tbaa [[TAG_A_i:!.*]]
@@ -54,6 +60,18 @@ int bar5(int j) {
     return AA[2] + AA[j];
 }
 
+int bar6(E *e, int j) {
+// CHECK-NEW-LABEL: _Z4bar6P1Ei
+// CHECK-NEW: load i32, {{.*}}, !tbaa [[TAG_E_x:!.*]]
+    return e->x[j];
+}
+
+int bar7(E *e, int j) {
+// CHECK-NEW-LABEL: _Z4bar7P1Ei
+// CHECK-NEW: load i32, {{.*}}, !tbaa [[TAG_E_y:!.*]]
+    return e->y[j];
+}
+
 // CHECK-DAG: [[TAG_A_i]] = !{[[TYPE_A:!.*]], [[TYPE_int:!.*]], i64 0}
 // CHECK-DAG: [[TYPE_A]] = !{!"_ZTS1A", !{{.*}}, i64 0}
 // CHECK-DAG: [[TYPE_int]] = !{!"int", !{{.*}}, i64 0}
@@ -64,5 +82,8 @@ int bar5(int j) {
 // CHECK-NEW-DAG: [[TYPE_A:!.*]] = !{[[TYPE_char]], i64 4, !"_ZTS1A", [[TYPE_int]], i64 0, i64 4}
 // CHECK-NEW-DAG: [[TAG_A_i]] = !{[[TYPE_A]], [[TYPE_int]], i64 0, i64 4}
 // CHECK-NEW-DAG: [[TYPE_C:!.*]] = !{[[TYPE_char]], i64 16, !"_ZTS1C", [[TYPE_int]], i64 0, i64 4, [[TYPE_int]], i64 4, i64 12}
-// CHECK-NEW-DAG: [[TAG_C_i]] = !{[[TYPE_C:!.*]], [[TYPE_int:!.*]], i64 0, i64 4}
-// CHECK-NEW-DAG: [[TAG_C_x]] = !{[[TYPE_C:!.*]], [[TYPE_int:!.*]], i64 4, i64 4}
+// CHECK-NEW-DAG: [[TAG_C_i]] = !{[[TYPE_C]], [[TYPE_int]], i64 0, i64 4}
+// CHECK-NEW-DAG: [[TAG_C_x]] = !{[[TYPE_C]], [[TYPE_int]], i64 4, i64 4}
+// CHECK-NEW-DAG: [[TYPE_E:!.*]] = !{[[TYPE_char]], i64 56, !"_ZTS1E", [[TYPE_char]], i64 0, i64 16, [[TYPE_char]], i64 16, i64 40}
+// CHECK-NEW-DAG: [[TAG_E_x]] = !{[[TYPE_E]], [[TYPE_char]], i64 0, i64 4}
+// CHECK-NEW-DAG: [[TAG_E_y]] = !{[[TYPE_E]], [[TYPE_char]], i64 16, i64 4}