1 files changed, 53 insertions, 0 deletions
diff --git a/pl/math/sv_powi.c b/pl/math/sv_powi.c
new file mode 100644
index 0000000..1bb0eb3
--- /dev/null
+++ b/pl/math/sv_powi.c
@@ -0,0 +1,53 @@
+/*
+ * Double-precision SVE powi(x, n) function.
+ *
+ * Copyright (c) 2020-2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#include "sv_math.h"
+#if SV_SUPPORTED
+
+/* Optimized double-precision vector powi (double base, long integer power).
+   powi is developed for environments in which accuracy is of much less
+   importance than performance, hence we provide no estimate for worst-case
+   error.  */
+svfloat64_t
+__sv_powi_x (svfloat64_t as, svint64_t ns, svbool_t p)
+{
+  /* Compute powi by successive squaring, right to left.  */
+  svfloat64_t acc = svdup_n_f64 (1.0);
+  svbool_t want_recip = svcmplt_n_s64 (p, ns, 0);
+  svuint64_t ns_abs = svreinterpret_u64_s64 (svabs_s64_x (p, ns));
+
+  /* We use a max to avoid needing to check whether any lane != 0 on each
+     iteration.  */
+  uint64_t max_n = svmaxv_u64 (p, ns_abs);
+
+  svfloat64_t c = as;
+  /* Successively square c, and use merging predication (_m) to determine
+     whether or not to perform the multiplication or keep the previous
+     iteration.  */
+  while (true)
+    {
+      svbool_t px = svcmpeq_n_u64 (p, svand_n_u64_x (p, ns_abs, 1ull), 1ull);
+      acc = svmul_f64_m (px, acc, c);
+      max_n >>= 1;
+      if (max_n == 0)
+	break;
+
+      ns_abs = svlsr_n_u64_x (p, ns_abs, 1);
+      c = svmul_f64_x (p, c, c);
+    }
+
+  /* Negative powers are handled by computing the abs(n) version and then
+     taking the reciprocal.  */
+  if (svptest_any (want_recip, want_recip))
+    acc = svdivr_n_f64_m (want_recip, acc, 1.0);
+
+  return acc;
+}
+
+strong_alias (__sv_powi_x, _ZGVsMxvv_powk)
+
+#endif // SV_SUPPORTED