================
@@ -0,0 +1,64 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++14 -triple
x86_64-unknown-unknown %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++14 -triple
x86_64-unknown-unknown %s -fexperimental-new-constant-interpreter
+
+constexpr int arr[10] = {};
+
+constexpr bool test_constexpr_valid() {
+ __builtin_assume_dereferenceable(arr, 40);
+ return true;
+}
+static_assert(test_constexpr_valid(), "");
+
+constexpr bool test_constexpr_partial() {
+ __builtin_assume_dereferenceable(&arr[5], 20);
+ return true;
+}
+static_assert(test_constexpr_partial(), "");
+
+constexpr bool test_constexpr_nullptr() {
+ __builtin_assume_dereferenceable(nullptr, 4);
+ return true;
+}
+static_assert(test_constexpr_nullptr(), ""); // expected-error {{not an
integral constant expression}}
+
+constexpr bool test_constexpr_too_large() {
+ __builtin_assume_dereferenceable(arr, 100);
+ return true;
+}
+static_assert(test_constexpr_too_large(), ""); // expected-error {{not an
integral constant expression}}
+
+constexpr int single_var = 42;
+constexpr bool test_single_var() {
+ __builtin_assume_dereferenceable(&single_var, 4);
+ return true;
+}
+static_assert(test_single_var(), "");
+
+constexpr bool test_exact_boundary() {
+ __builtin_assume_dereferenceable(&arr[9], 4);
+ return true;
+}
+static_assert(test_exact_boundary(), "");
+
+constexpr bool test_one_over() {
+ __builtin_assume_dereferenceable(&arr[9], 5);
+ return true;
+}
+static_assert(test_one_over(), ""); // expected-error {{not an integral
constant expression}}
+
+constexpr bool test_zero_size() {
+ __builtin_assume_dereferenceable(arr, 0);
+ return true;
+}
+static_assert(test_zero_size(), ""); // expected-error {{not an integral
constant expression}}
+
+struct S {
+ int x;
+ int y;
+};
+constexpr S s = {1, 2};
+constexpr bool test_struct_member() {
+ __builtin_assume_dereferenceable(&s.x, 4);
+ return true;
+}
+static_assert(test_struct_member(), "");
----------------
tbaederr wrote:
Right, I thought the builtin meant "we can dereference that pointer and read X
bytes from it", not "starting from that pointer, X bytes can be read" (the
latter meaning we can basically to a memcpy from it).
What about
```c++
int b = 10;
const int f = (__builtin_assume_dereferenceable((char*)&b + 1, 3), 12);
int a = f;
```
, shouldn't that work?
https://github.com/llvm/llvm-project/pull/169869
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