Merged with libbbid branch at revision 126349.

[pf3gnuchains/gcc-fork.git] / libgcc / config / libbid / bid128_logb.c

diff --git a/libgcc/config/libbid/bid128_logb.c b/libgcc/config/libbid/bid128_logb.c
new file mode 100644 (file)
index 0000000..38e22ae
--- /dev/null
+++ b/libgcc/config/libbid/bid128_logb.c
@@ -0,0 +1,86 @@
+/* Copyright (C) 2007  Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+In addition to the permissions in the GNU General Public License, the
+Free Software Foundation gives you unlimited permission to link the
+compiled version of this file into combinations with other programs,
+and to distribute those combinations without any restriction coming
+from the use of this file.  (The General Public License restrictions
+do apply in other respects; for example, they cover modification of
+the file, and distribution when not linked into a combine
+executable.)
+
+GCC 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 General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
+
+#define BID_128RES
+#include "bid_internal.h"
+
+BID128_FUNCTION_ARG1(__bid128_logb, x)
+
+  UINT128 CX, L, res;
+  UINT64 sign_x, sign_e, logb_sign;
+  SINT64 D;
+  int_float f64, fx;
+  int exponent_x, bin_expon_cx, digits;
+
+  if (!unpack_BID128_value (&sign_x, &exponent_x, &CX, x)) {
+    res.w[1] = x.w[1];
+    res.w[0] = x.w[0];
+    // x is Infinity?
+    if ((x.w[1] & 0x7800000000000000ull) == 0x7800000000000000ull) {
+      if ((x.w[1] & 0x7c00000000000000ull) != 0x7c00000000000000ull)
+        // +/-Inf, return Inf
+        res.w[1] = 0x7800000000000000ull;
+      BID_RETURN (res);
+    }
+    // x is 0 otherwise
+
+#ifdef SET_STATUS_FLAGS
+    // set status flags
+    __set_status_flags (pfpsf, ZERO_DIVIDE_EXCEPTION);
+#endif
+    res.w[1] = 0xf800000000000000ull;
+    res.w[0] = 0;
+    BID_RETURN (res);
+  }
+  // find number of digits in coefficient
+  // 2^64
+  f64.i = 0x5f800000;
+  // fx ~ CX
+  fx.d = (float) CX.w[1] * f64.d + (float) CX.w[0];
+  bin_expon_cx = ((fx.i >> 23) & 0xff) - 0x7f;
+  digits = __bid_estimate_decimal_digits[bin_expon_cx];
+  // scale = 38-__bid_estimate_decimal_digits[bin_expon_cx];
+  D = CX.w[1] - __bid_power10_index_binexp_128[bin_expon_cx].w[1];
+  if (D > 0
+      || (!D && CX.w[0] >= __bid_power10_index_binexp_128[bin_expon_cx].w[0]))
+    digits++;
+
+  exponent_x = exponent_x - DECIMAL_EXPONENT_BIAS_128 - 1 + digits;
+
+  // extract sign and absolute value from exponent_x
+  sign_e = ((SINT32) exponent_x) >> 31;
+  exponent_x = (exponent_x + sign_e) ^ sign_e;
+
+  L.w[0] = exponent_x;
+  L.w[1] = 0;
+  logb_sign = sign_e << 63;
+
+  get_BID128_very_fast (&res, logb_sign, DECIMAL_EXPONENT_BIAS_128, L);
+  BID_RETURN (res);
+
+}