[src/get_si.c] Code refactoring/simplification like what has been

done for get_ui.c in r13185, fixing also an integer overflow when
MPFR_LONG_WITHIN_LIMB is not defined.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@13200 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 18 insertions, 30 deletions

diff --git a/src/get_si.c b/src/get_si.c
index eff3c33a2..05ccecce6 100644
--- a/src/get_si.c
+++ b/src/get_si.c
@@ -57,44 +57,32 @@ mpfr_get_si (mpfr_srcptr f, mpfr_rnd_t rnd)
   MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
 
   /* warning: if x=0, taking its exponent is illegal */
-  if (MPFR_UNLIKELY (MPFR_IS_ZERO(x)))
+  if (MPFR_IS_ZERO (x))
     s = 0;
   else
-#ifdef MPFR_LONG_WITHIN_LIMB
     {
-      mp_limb_t a;
+      unsigned long u = 0;
       mp_size_t n;
       mpfr_exp_t exp;
 
-      /* now the result is in the most significant limb of x */
-      exp = MPFR_GET_EXP (x); /* since |x| >= 1, exp >= 1 */
-      n = MPFR_LIMB_SIZE(x);
-      a = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
-      s = MPFR_IS_POS (f) ? a : a <= LONG_MAX ? - (long) a : LONG_MIN;
-    }
+      exp = MPFR_GET_EXP (x);
+      MPFR_ASSERTD (exp >= 1); /* since |x| >= 1 */
+      n = MPFR_LIMB_SIZE (x);
+#ifdef MPFR_LONG_WITHIN_LIMB
+      MPFR_ASSERTD (exp <= GMP_NUMB_BITS);
 #else
-  {
-    mp_size_t n;
-    mpfr_exp_t exp;
-
-    exp = MPFR_GET_EXP (x);
-    n = MPFR_LIMB_SIZE(x);
-    /* invariant: the current word x[n-1] has to be multiplied by
-       2^(exp - GMP_NUMB_BITS) */
-    s = 0;
-    while (exp > 0)
-      {
-        MPFR_ASSERTD(n > 0);
-        if (exp <= GMP_NUMB_BITS)
-          s += MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
-        else
-          s += (unsigned long) MPFR_MANT(x)[n - 1] << (exp - GMP_NUMB_BITS);
-        n --;
-        exp -= GMP_NUMB_BITS;
-      }
-    s = MPFR_IS_POS (f) ? s : s <= LONG_MAX ? - (long) s : LONG_MIN;
-  }
+      while (exp > GMP_NUMB_BITS)
+        {
+          MPFR_ASSERTD (n > 0);
+          u += (unsigned long) MPFR_MANT(x)[n - 1] << (exp - GMP_NUMB_BITS);
+          n--;
+          exp -= GMP_NUMB_BITS;
+        }
 #endif
+      MPFR_ASSERTD (n > 0);
+      u += MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
+      s = MPFR_IS_POS (f) ? u : u <= LONG_MAX ? - (long) u : LONG_MIN;
+    }
 
   mpfr_clear (x);