1 files changed, 64 insertions, 0 deletions
diff --git a/sysdeps/powerpc/fpu/s_logb.c b/sysdeps/powerpc/fpu/s_logb.c
new file mode 100644
index 0000000000..364f7f0cc3
--- /dev/null
+++ b/sysdeps/powerpc/fpu/s_logb.c
@@ -0,0 +1,64 @@
+/* Get exponent of a floating-point value.  PowerPC version.
+   Copyright (C) 2012-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* ISA 2.07 provides fast GPR to FP instruction (mfvsr{d,wz}) which make
+   generic implementation faster.  */
+#if defined(_ARCH_PWR8) || !defined(_ARCH_PWR7)
+# include <sysdeps/ieee754/dbl-64/s_logb.c>
+#else
+# include <math.h>
+# include <math_private.h>
+# include <math_ldbl_opt.h>
+# include <libm-alias-double.h>
+
+/* This implementation avoids FP to INT conversions by using VSX
+   bitwise instructions over FP values.  */
+double
+__logb (double x)
+{
+  double ret;
+
+  if (__glibc_unlikely (x == 0.0))
+    /* Raise FE_DIVBYZERO and return -HUGE_VAL[LF].  */
+    return -1.0 / fabs (x);
+
+  /* Mask to extract the exponent.  */
+  asm ("xxland %x0,%x1,%x2\n"
+       "fcfid  %0,%0"
+       : "=d" (ret)
+       : "d" (x), "d" (0x7ff0000000000000ULL));
+  ret = (ret * 0x1p-52) - 1023.0;
+  if (ret > 1023.0)
+    /* Multiplication is used to set logb (+-INF) = INF.  */
+    return (x * x);
+  else if (ret == -1023.0)
+    {
+      /* POSIX specifies that denormal numbers are treated as
+         though they were normalized.  */
+      int64_t ix;
+      EXTRACT_WORDS64 (ix, x);
+      ix &= UINT64_C (0x7fffffffffffffff);
+      return (double) (-1023 - (__builtin_clzll (ix) - 12));
+    }
+  /* Test to avoid logb_downward (0.0) == -0.0.  */
+  return ret == -0.0 ? 0.0 : ret;
+}
+# ifndef __logb
+libm_alias_double (__logb, logb)
+# endif
+#endif