[tests/tfmma.c] Merged the latest tests from the trunk

  (r12752,12759,13688,13696).
[src/sub1.c] Bug fix: the underflow case (possible with UBF, e.g. via
  mpfr_fmma or mpfr_fmms) was not tested in the case c small.
  (merged changeset r13694 from the trunk)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/branches/4.0@13697 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 114 insertions, 10 deletions

diff --git a/src/sub1.c b/src/sub1.c
index 9337cc235..5b475d9d3 100644
--- a/src/sub1.c
+++ b/src/sub1.c
@@ -123,11 +123,11 @@ mpfr_sub1 (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
       if (rnd_mode == MPFR_RNDF)
         return mpfr_set4 (a, b, MPFR_RNDZ, MPFR_SIGN (a));
 
-      MPFR_EXP (a) = exp_b;  /* may be up to MPFR_EXP_MAX */
+      exp_a = exp_b;  /* may be any out-of-range value due to UBF */
       MPFR_RNDRAW_EVEN (inexact, a, MPFR_MANT (b), bq,
                         rnd_mode, MPFR_SIGN (a),
-                        if (MPFR_EXP (a) != MPFR_EXP_MAX)
-                          ++ MPFR_EXP (a));
+                        if (exp_a != MPFR_EXP_MAX)
+                          exp_a ++);
       MPFR_LOG_MSG (("inexact=%d\n", inexact));
       if (inexact == 0)
         {
@@ -139,7 +139,7 @@ mpfr_sub1 (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
           if (! MPFR_IS_LIKE_RNDZ (rnd_mode, MPFR_IS_NEG (a)))
             {
               inexact = MPFR_INT_SIGN (a);
-              goto check_overflow;
+              goto end_of_c_small;
             }
         }
       else  /* inexact != 0 */
@@ -164,7 +164,7 @@ mpfr_sub1 (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
              which means we get a wrong rounded result if x == 1,
              i.e. inexact == MPFR_EVEN_INEX (for positive numbers). */
           if (MPFR_LIKELY (inexact != MPFR_EVEN_INEX * MPFR_INT_SIGN (a)))
-            goto check_overflow;
+            goto end_of_c_small;
         }
       /* We need to take the value preceding |a|. We can't use
          mpfr_nexttozero due to a possible out-of-range exponent.
@@ -174,16 +174,20 @@ mpfr_sub1 (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
       mpn_sub_1 (ap, ap, an, MPFR_LIMB_ONE << sh);
       if (MPFR_UNLIKELY (MPFR_LIMB_MSB (ap[an-1]) == 0))
         {
-          MPFR_EXP (a) --;
+          exp_a --;
           /* The following is valid whether an = 1 or an > 1. */
           ap[an-1] |= MPFR_LIMB_HIGHBIT;
         }
       inexact = - MPFR_INT_SIGN (a);
-    check_overflow:
-      if (MPFR_UNLIKELY (MPFR_EXP (a) > __gmpfr_emax))
+    end_of_c_small:
+      /* The underflow case is possibly only with UBF. The overflow case
+         is also possible with normal FP due to rounding. */
+      if (MPFR_UNLIKELY (exp_a > __gmpfr_emax))
         return mpfr_overflow (a, rnd_mode, MPFR_SIGN (a));
-      else
-        MPFR_RET (inexact);
+      if (MPFR_UNLIKELY (exp_a < __gmpfr_emin))
+        goto underflow;
+      MPFR_SET_EXP (a, exp_a);
+      MPFR_RET (inexact);
     }
 
   /* reserve a space to store b aligned with the result, i.e. shifted by
diff --git a/tests/tfmma.c b/tests/tfmma.c
index 602603377..a4243cca2 100644
--- a/tests/tfmma.c
+++ b/tests/tfmma.c
@@ -480,6 +480,103 @@ bug20170405 (void)
   mpfr_clears (x, y, z, (mpfr_ptr) 0);
 }
 
+static void
+underflow_tests (void)
+{
+  mpfr_t x, y, z;
+  mpfr_prec_t p;
+  mpfr_exp_t emin;
+
+  emin = mpfr_get_emin ();
+  mpfr_set_emin (-17);
+  for (p = MPFR_PREC_MIN; p <= 1024; p++)
+    {
+      mpfr_inits2 (p, x, y, (mpfr_ptr) 0);
+      mpfr_init2 (z, p + 1);
+      mpfr_set_str_binary (x, "1e-10");
+      mpfr_set_str_binary (y, "1e-11");
+      mpfr_clear_underflow ();
+      mpfr_fmms (z, x, x, y, y, MPFR_RNDN);
+      /* the exact result is 2^-20-2^-22, and should underflow */
+      MPFR_ASSERTN(mpfr_underflow_p ());
+      MPFR_ASSERTN(mpfr_zero_p (z));
+      MPFR_ASSERTN(mpfr_signbit (z) == 0);
+      mpfr_clears (x, y, z, (mpfr_ptr) 0);
+    }
+  mpfr_set_emin (emin);
+}
+
+static void
+bug20180604 (void)
+{
+  mpfr_t x, y, yneg, z;
+  mpfr_exp_t emin;
+  int ret;
+
+  emin = mpfr_get_emin ();
+  mpfr_set_emin (-1073741821);
+  mpfr_inits2 (564, x, y, yneg, (mpfr_ptr) 0);
+  mpfr_init2 (z, 2256);
+  mpfr_set_str_binary (x, "1.10010000111100110011001101111111101000111001011000110100110010000101000100010001000000111100010000101001011011111001111000110101111100101111001100001100011101100100011110000000011000010110111100111000100101010001011111010111011001110010001011101111001011001110110000010000011100010001010001011100100110111110101001001111001011101111110011101110101010110100010010111011111100010101111100011110111001011111101110101101101110100101111010000101011110100000000110111101000001100001000100010110100111010011011010110011100111010000101110010101111001011100110101100001100E-737194993");
+  mpfr_set_str_binary (y, "-1.00101000100001001101011110100010110011101010011011010111100110101011111100000100101000111010111101100100110010001110011011100100110110000001011001000111101111101111110101100110111000000011000001101001010100010010001110001000011010000100111001001100101111111100010101110101001101101101111010100011011110001000010000010100011000011000010110101100000111111110111001100100100001101011111011100101110111000100101010110100010011101010110010100110100111000000100111101101101000000011110000100110100100011000010011110010001010000110100011111101101101110001110001101101010E-737194903");
+
+  mpfr_clear_underflow ();
+  ret = mpfr_fmms (z, x, x, y, y, MPFR_RNDN);
+  MPFR_ASSERTN(mpfr_underflow_p ());
+  MPFR_ASSERTN(mpfr_zero_p (z));
+  MPFR_ASSERTN(mpfr_signbit (z) == 1);
+  MPFR_ASSERTN(ret > 0);
+
+  mpfr_clear_underflow ();
+  ret = mpfr_fmms (z, y, y, x, x, MPFR_RNDN);
+  MPFR_ASSERTN(mpfr_underflow_p ());
+  MPFR_ASSERTN(mpfr_zero_p (z));
+  MPFR_ASSERTN(mpfr_signbit (z) == 0);
+  MPFR_ASSERTN(ret < 0);
+
+  mpfr_neg (yneg, y, MPFR_RNDN);
+  mpfr_clear_underflow ();
+  ret = mpfr_fmms (z, x, x, y, yneg, MPFR_RNDN);
+  MPFR_ASSERTN(mpfr_underflow_p ());
+  MPFR_ASSERTN(mpfr_zero_p (z));
+  MPFR_ASSERTN(mpfr_signbit (z) == 0);
+  MPFR_ASSERTN(ret < 0);
+
+  mpfr_clear_underflow ();
+  ret = mpfr_fmms (z, y, yneg, x, x, MPFR_RNDN);
+  MPFR_ASSERTN(mpfr_underflow_p ());
+  MPFR_ASSERTN(mpfr_zero_p (z));
+  MPFR_ASSERTN(mpfr_signbit (z) == 1);
+  MPFR_ASSERTN(ret > 0);
+
+  mpfr_clears (x, y, yneg, z, (mpfr_ptr) 0);
+  mpfr_set_emin (emin);
+}
+
+/* this bug was discovered from mpc_mul */
+static void
+bug20200206 (void)
+{
+  mpfr_exp_t emin = mpfr_get_emin ();
+  mpfr_t xre, xim, yre, yim, zre;
+
+  mpfr_set_emin (-1073);
+  mpfr_inits2 (53, xre, xim, yre, yim, zre, (mpfr_ptr) 0);
+  mpfr_set_str (xre, "-0x8.294611b331c8p-904", 16, MPFR_RNDN);
+  mpfr_set_str (xim, "-0x1.859278c2992fap-676", 16, MPFR_RNDN);
+  mpfr_set_str (yre, "0x9.ac54802a95f8p-820", 16, MPFR_RNDN);
+  mpfr_set_str (yim, "0x3.17e59e7612aap-412", 16, MPFR_RNDN);
+  mpfr_fmms (zre, xre, yre, xim, yim, MPFR_RNDN);
+  if (mpfr_regular_p (zre) && mpfr_get_exp (zre) < -1073)
+    {
+      printf ("Error, mpfr_fmms returns an out-of-range exponent:\n");
+      mpfr_dump (zre);
+      exit (1);
+    }
+  mpfr_clears (xre, xim, yre, yim, zre, (mpfr_ptr) 0);
+  mpfr_set_emin (emin);
+}
+
 /* Test double-rounding cases in mpfr_set_1_2, which is called when
    all the precisions are the same. With set.c before r13347, this
    triggers errors for neg=0. */
@@ -548,6 +645,9 @@ main (int argc, char *argv[])
 {
   tests_start_mpfr ();
 
+  bug20200206 ();
+  bug20180604 ();
+  underflow_tests ();
   random_tests ();
   zero_tests ();
   max_tests ();