1 files changed, 56 insertions, 0 deletions
diff --git a/sysdeps/powerpc/fpu/s_logbf.c b/sysdeps/powerpc/fpu/s_logbf.c
new file mode 100644
index 0000000000..cf564ad294
--- /dev/null
+++ b/sysdeps/powerpc/fpu/s_logbf.c
@@ -0,0 +1,56 @@
+/* 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/flt-32/s_logbf.c>
+#else
+# include <math.h>
+# include <libm-alias-float.h>
+/* This implementation avoids FP to INT conversions by using VSX
+   bitwise instructions over FP values.  */
+float
+__logbf (float x)
+{
+  /* VSX operation are all done internally as double.  */
+  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 >> 52) - 1023.0, since ret is double.  */
+  ret = (ret * 0x1p-52) - 1023.0;
+  if (ret > 127.0)
+    /* Multiplication is used to set logb (+-INF) = INF.  */
+    return (x * x);
+  /* Since operations are done with double we don't need
+     additional tests for subnormal numbers.
+     The test is to avoid logb_downward (0.0) == -0.0.  */
+  return ret == -0.0 ? 0.0 : ret;
+}
+# ifndef __logbf
+libm_alias_float (__logb, logb)
+# endif
+#endif