Add another C++14 constexpr test case.

llvm-svn: 187096

clang/test/SemaCXX/constexpr-duffs-device.cpp

@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -std=c++1y -verify %s
+
+// expected-no-diagnostics
+constexpr void copy(const char *from, unsigned long count, char *to) {
+        unsigned long n = (count + 7) / 8;
+        switch(count % 8) {
+        case 0: do {    *to++ = *from++;
+        case 7:         *to++ = *from++;
+        case 6:         *to++ = *from++;
+        case 5:         *to++ = *from++;
+        case 4:         *to++ = *from++;
+        case 3:         *to++ = *from++;
+        case 2:         *to++ = *from++;
+        case 1:         *to++ = *from++;
+                } while(--n > 0);
+        }
+}
+
+struct S {
+  char stuff[14];
+  constexpr S() : stuff{} {
+    copy("Hello, world!", 14, stuff);
+  }
+};
+
+constexpr bool streq(const char *a, const char *b) {
+  while (*a && *a == *b) ++a, ++b;
+  return *a == *b;
+}
+
+static_assert(streq(S().stuff, "Hello, world!"), "should be same");
+static_assert(!streq(S().stuff, "Something else"), "should be different");