Add Chromium-only Blender WebEngine parity work

blender-5.2.0/extern/gmp-source/mpn/generic/powlo.c

@@ -0,0 +1,188 @@
+/* mpn_powlo -- Compute R = U^E mod B^n, where B is the limb base.
+
+Copyright 2007-2009, 2012, 2015, 2016, 2018, 2020 Free Software
+Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP 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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+#define getbit(p,bi) \
+  ((p[(bi - 1) / GMP_LIMB_BITS] >> (bi - 1) % GMP_LIMB_BITS) & 1)
+
+static inline mp_limb_t
+getbits (const mp_limb_t *p, mp_bitcnt_t bi, unsigned nbits)
+{
+  unsigned nbits_in_r;
+  mp_limb_t r;
+  mp_size_t i;
+
+  if (bi <= nbits)
+    {
+      return p[0] & (((mp_limb_t) 1 << bi) - 1);
+    }
+  else
+    {
+      bi -= nbits;			/* bit index of low bit to extract */
+      i = bi / GMP_NUMB_BITS;		/* word index of low bit to extract */
+      bi %= GMP_NUMB_BITS;		/* bit index in low word */
+      r = p[i] >> bi;			/* extract (low) bits */
+      nbits_in_r = GMP_NUMB_BITS - bi;	/* number of bits now in r */
+      if (nbits_in_r < nbits)		/* did we get enough bits? */
+	r += p[i + 1] << nbits_in_r;	/* prepend bits from higher word */
+      return r & (((mp_limb_t) 1 << nbits) - 1);
+    }
+}
+
+static inline unsigned
+win_size (mp_bitcnt_t eb)
+{
+  unsigned k;
+  static mp_bitcnt_t x[] = {7,25,81,241,673,1793,4609,11521,28161,~(mp_bitcnt_t)0};
+  ASSERT (eb > 1);
+  for (k = 0; eb > x[k++];)
+    ;
+  return k;
+}
+
+/* rp[n-1..0] = bp[n-1..0] ^ ep[en-1..0] mod B^n, B is the limb base.
+   Requires that ep[en-1] is non-zero.
+   Uses scratch space tp[3n-1..0], i.e., 3n words.  */
+/* We only use n words in the scratch space, we should pass tp + n to
+   mullo/sqrlo as a temporary area, it is needed. */
+void
+mpn_powlo (mp_ptr rp, mp_srcptr bp,
+	   mp_srcptr ep, mp_size_t en,
+	   mp_size_t n, mp_ptr tp)
+{
+  unsigned cnt;
+  mp_bitcnt_t ebi;
+  unsigned windowsize, this_windowsize;
+  mp_limb_t expbits;
+  mp_limb_t *pp;
+  long i;
+  int flipflop;
+  TMP_DECL;
+
+  ASSERT (en > 1 || (en == 1 && ep[0] > 1));
+
+  TMP_MARK;
+
+  MPN_SIZEINBASE_2EXP(ebi, ep, en, 1);
+
+  windowsize = win_size (ebi);
+  if (windowsize > 1)
+    {
+      mp_limb_t *this_pp, *last_pp;
+      ASSERT (windowsize < ebi);
+
+      pp = TMP_ALLOC_LIMBS ((n << (windowsize - 1)));
+
+      this_pp = pp;
+
+      MPN_COPY (this_pp, bp, n);
+
+      /* Store b^2 in tp.  */
+      mpn_sqrlo (tp, bp, n);
+
+      /* Precompute odd powers of b and put them in the temporary area at pp.  */
+      i = (1 << (windowsize - 1)) - 1;
+      do
+	{
+	  last_pp = this_pp;
+	  this_pp += n;
+	  mpn_mullo_n (this_pp, last_pp, tp, n);
+	} while (--i != 0);
+
+      expbits = getbits (ep, ebi, windowsize);
+      ebi -= windowsize;
+
+      /* THINK: Should we initialise the case expbits % 4 == 0 with a mullo? */
+      count_trailing_zeros (cnt, expbits);
+      ebi += cnt;
+      expbits >>= cnt;
+
+      MPN_COPY (rp, pp + n * (expbits >> 1), n);
+    }
+  else
+    {
+      pp = tp + n;
+      MPN_COPY (pp, bp, n);
+      MPN_COPY (rp, bp, n);
+      --ebi;
+    }
+
+  flipflop = 0;
+
+  do
+    {
+      while (getbit (ep, ebi) == 0)
+	{
+	  mpn_sqrlo (tp, rp, n);
+	  MP_PTR_SWAP (rp, tp);
+	  flipflop = ! flipflop;
+	  if (--ebi == 0)
+	    goto done;
+	}
+
+      /* The next bit of the exponent is 1.  Now extract the largest block of
+	 bits <= windowsize, and such that the least significant bit is 1.  */
+
+      expbits = getbits (ep, ebi, windowsize);
+      this_windowsize = MIN (windowsize, ebi);
+
+      count_trailing_zeros (cnt, expbits);
+      this_windowsize -= cnt;
+      ebi -= this_windowsize;
+      expbits >>= cnt;
+
+      while (this_windowsize > 1)
+	{
+	  mpn_sqrlo (tp, rp, n);
+	  mpn_sqrlo (rp, tp, n);
+	  this_windowsize -= 2;
+	}
+
+      if (this_windowsize != 0)
+	mpn_sqrlo (tp, rp, n);
+      else
+	{
+	  MP_PTR_SWAP (rp, tp);
+	  flipflop = ! flipflop;
+	}
+
+      mpn_mullo_n (rp, tp, pp + n * (expbits >> 1), n);
+    } while (ebi != 0);
+
+ done:
+  if (flipflop)
+    MPN_COPY (tp, rp, n);
+  TMP_FREE;
+}