Add C++ implementations for xLACGV - conjugate a vector.

PiperOrigin-RevId: 380897960

lapack/experimental/xlacgv.cpp

diff --git a/lapack/experimental/xlacgv.cpp b/lapack/experimental/xlacgv.cpp
new file mode 100644
index 0000000..d022a3b
--- /dev/null
+++ b/lapack/experimental/xlacgv.cpp
@@ -0,0 +1,27 @@
+#include "../../Eigen/Core"
+
+extern "C" {
+void clacgv_(int *n, std::complex<float> *x, int *incx);
+void zlacgv_(int *n, std::complex<double> *x, int *incx);
+}
+
+using Eigen::Map;
+using Eigen::Matrix;
+using Eigen::Dynamic;
+using Eigen::InnerStride;
+
+// Conjugate the entries of the vector x.
+template <typename T>
+void xlacgv(const int n,  T *x, const int incx) {
+  using StridedVector = Map<Matrix<T, Dynamic, 1>, 0, InnerStride<Dynamic>>;
+  StridedVector xvec(x, n, InnerStride<Dynamic>(std::abs(incx)));
+  xvec = xvec.conjugate();
+}
+
+void clacgv_(int *n, std::complex<float> *x, int *incx) {
+  xlacgv(*n, x, *incx);
+}
+
+void zlacgv_(int *n, std::complex<double> *x, int *incx) {
+  xlacgv(*n, x, *incx);
+}