C++ implementation of xSECND using time.h

PiperOrigin-RevId: 380898512

lapack/experimental/xsecnd.cpp

diff --git a/lapack/experimental/xsecnd.cpp b/lapack/experimental/xsecnd.cpp
new file mode 100644
index 0000000..d9e3879
--- /dev/null
+++ b/lapack/experimental/xsecnd.cpp
@@ -0,0 +1,16 @@
+#include <ctime>
+
+extern "C" {
+float second_();
+double dsecnd_();
+}
+
+// Elapsed CPU Time in seconds.
+float second_(float* x, float* y) {
+  return static_cast<float>(std::clock()) / static_cast<float>(CLOCKS_PER_SEC);
+}
+
+double dsecnd_(double* x, double* y) {
+  return static_cast<double>(std::clock()) /
+         static_cast<double>(CLOCKS_PER_SEC);
+}