Add codegen tests to verify constexpr passthrough for non-constexpr const initialization

Author: chaitanyav

clang/test/CodeGenCXX/builtin-assume-dereferenceable-constexpr.cpp

@@ -0,0 +1,50 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --include-generated-funcs
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -std=c++14 -emit-llvm -o - %s | FileCheck %s
+
+constexpr int b = 10;
+int test_char_cast() {
+  const int f = (__builtin_assume_dereferenceable((char*)&b + 1, 3), 12);
+  return f;
+}
+
+constexpr long long ll = 100;
+int test_void_cast() {
+  const int h = (__builtin_assume_dereferenceable((void*)&ll, 8), 99);
+  return h;
+}
+
+constexpr int gb = 10;
+const int gf = (__builtin_assume_dereferenceable((char*)&gb + 1, 3), 12);
+int ga = gf;
+
+// CHECK-LABEL: test_char_castv
+// CHECK:         [[F:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    call void @llvm.assume(i1 true) [ "dereferenceable"(ptr getelementptr inbounds (i8, ptr @_ZL1b, i64 1), i64 3) ]
+// CHECK-NEXT:    store i32 12, ptr [[F]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[F]], align 4
+// CHECK-NEXT:    ret i32 [[TMP0]]
+//
+//
+// CHECK-LABEL: test_void_castv
+// CHECK:         [[H:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i32 99, ptr [[H]], align 4
+// CHECK-NEXT:    ret i32 99
+//
+//
+// CHECK-LABEL: __cxx_global_var_init
+// CHECK:         [[TMP0:%.*]] = load i32, ptr @_ZL2gf, align 4
+// CHECK-NEXT:    store i32 [[TMP0]], ptr @ga, align 4
+// CHECK-NEXT:    ret void
+//
+//
+// CHECK-LABEL: __cxx_global_var_init.1
+// CHECK:         call void @llvm.assume(i1 true) [ "dereferenceable"(ptr getelementptr inbounds (i8, ptr @_ZL2gb, i64 1), i64 3) ]
+// CHECK-NEXT:    store i32 12, ptr @_ZL2gf, align 4
+// CHECK-NEXT:    ret void
+//
+//
+// CHECK-LABEL: _GLOBAL__sub_I_builtin_assume_dereferenceable_constexpr.cpp
+// CHECK:         call void @__cxx_global_var_init.1()
+// CHECK-NEXT:    call void @__cxx_global_var_init()
+// CHECK-NEXT:    ret void
+//

clang/test/SemaCXX/builtin-assume-dereferenceable-constexpr.cpp

@@ -58,8 +58,8 @@ static_assert(test_zero_size(), "");
 
 constexpr bool test_struct_member() {
   struct S {
-    int x;
-    int y;
+  int x;
+  int y;
   };
   constexpr S s = {1, 2};
   __builtin_assume_dereferenceable(&s.x, 4);
@@ -90,24 +90,3 @@ constexpr int arr2[5] = {1, 2, 3, 4, 5};
 constexpr int too_large = (__builtin_assume_dereferenceable(arr2, 6 * sizeof(int)), 12); // expected-error {{constexpr variable 'too_large' must be initialized by a constant expression}} expected-note {{read of dereferenced one-past-the-end pointer is not allowed in a constant expression}}
 
 constexpr int null = (__builtin_assume_dereferenceable(nullptr, 4), 12); // expected-error {{constexpr variable 'null' must be initialized by a constant expression}} expected-note {{read of dereferenced null pointer is not allowed in a constant expression}}
-
-int b = 10;
-const int f = (__builtin_assume_dereferenceable((char*)&b + 1, 3), 12);
-int a = f;
-
-int c[10] = {};
-const int g = (__builtin_assume_dereferenceable((unsigned char*)c + 5, 35), 42);
-int d = g;
-
-long long ll = 100;
-const int h = (__builtin_assume_dereferenceable((void*)&ll, 8), 99);
-int e = h;
-
-struct Foo { int x; int y; int z; };
-Foo foo = {1, 2, 3};
-const int i = (__builtin_assume_dereferenceable((short*)&foo + 2, 8), 77);
-int j = i;
-
-double darr[10] = {};
-const int k = (__builtin_assume_dereferenceable((int*)darr, 40), 55);
-int l = k;