Hi!
So, apparently I've misread when exceptions are raised by
nextafter/nexttoward (and errno set).
if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
return x+y;
I believe the above only raises exception if either operand is sNaN and thus
we should handle it:
if (REAL_VALUE_ISSIGNALING_NAN (*arg0)
|| REAL_VALUE_ISSIGNALING_NAN (*arg1))
return false;
Then:
if(x==y) return y; /* x=y, return y */
If arguments are equal, no exception is raised even if it is denormal,
we handle this with:
/* If x == y, return y cast to target type. */
if (cmp == 0)
{
real_convert (r, fmt, y);
return false;
}
Next:
if((ix|lx)==0) { /* x == 0 */
double u;
INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
u = math_opt_barrier (x);
u = u*u;
math_force_eval (u); /* raise underflow flag */
return x;
}
going from zero to +/- ulp should only raise underflow, but not set errno,
handled with:
/* Similarly for nextafter (0, 1) raising underflow. */
else if (flag_trapping_math
&& arg0->cl == rvc_zero
&& result->cl != rvc_zero)
return false;
Then overflow:
hy = hx&0x7ff00000;
if(hy>=0x7ff00000) {
double u = x+x; /* overflow */
math_force_eval (u);
__set_errno (ERANGE);
}
should be handled with:
if (REAL_EXP (r) > fmt->emax)
{
get_inf (r, x->sign);
return true;
}
And finally there is:
if(hy<0x00100000) {
double u = x*x; /* underflow */
math_force_eval (u); /* raise underflow flag */
__set_errno (ERANGE);
}
which I've misread as raising exception and setting errno only if
the result is 0 and first arg isn't:
return r->cl == rvc_zero;
but actually it is true also for all denormal returns except for the x == y
case, so the following patch uses:
return r->cl == rvc_zero || REAL_EXP (r) < fmt->emin;
instead.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-07-07 Jakub Jelinek <[email protected]>
PR c/86420
* real.c (real_nextafter): Return true if result is denormal.
* gcc.dg/nextafter-1.c (TEST): Adjust the tests that expect denormals
to be returned and when first argument is not 0, so that they don't do
anything for NEED_EXC or NEED_ERRNO.
--- gcc/real.c.jj 2018-05-06 23:12:49.211619736 +0200
+++ gcc/real.c 2018-07-06 18:42:44.761026632 +0200
@@ -5141,7 +5141,7 @@ real_nextafter (REAL_VALUE_TYPE *r, form
get_zero (r, x->sign);
return true;
}
- return r->cl == rvc_zero;
+ return r->cl == rvc_zero || REAL_EXP (r) < fmt->emin;
}
/* Write into BUF the maximum representable finite floating-point
--- gcc/testsuite/gcc.dg/nextafter-1.c.jj 2018-05-10 09:38:03.040250709
+0200
+++ gcc/testsuite/gcc.dg/nextafter-1.c 2018-07-06 19:17:55.138355524 +0200
@@ -58,23 +58,41 @@ name (void)
\
= (NEED_EXC || NEED_ERRNO) ? __builtin_inf##l1 () \
: fn (MAX1, __builtin_inf ()); \
CHECK (__builtin_isinf##l1 (m) && !__builtin_signbit (m)); \
- const type n = fn (DENORM_MIN1, 12.0##L2); \
+ const type n \
+ = (NEED_EXC || NEED_ERRNO) ? 2.0##L1 * DENORM_MIN1 \
+ : fn (DENORM_MIN1, 12.0##L2); \
CHECK (n == 2.0##L1 * DENORM_MIN1); \
- const type o = fn (n, 24.0##L2); \
+ const type o \
+ = (NEED_EXC || NEED_ERRNO) ? 3.0##L1 * DENORM_MIN1 \
+ : fn (n, 24.0##L2); \
CHECK (o == 3.0##L1 * DENORM_MIN1); \
- const type p = fn (o, 132.0##L2); \
+ const type p \
+ = (NEED_EXC || NEED_ERRNO) ? 4.0##L1 * DENORM_MIN1 \
+ : fn (o, 132.0##L2); \
CHECK (p == 4.0##L1 * DENORM_MIN1); \
- const type q = fn (2.0##L1 * DENORM_MIN1, -__builtin_inf ());
\
+ const type q \
+ = (NEED_EXC || NEED_ERRNO) ? DENORM_MIN1 \
+ : fn (2.0##L1 * DENORM_MIN1, -__builtin_inf ()); \
CHECK (q == DENORM_MIN1); \
- const type r = fn (3.0##L1 * DENORM_MIN1, DENORM_MIN2); \
+ const type r \
+ = (NEED_EXC || NEED_ERRNO) ? 2.0##L1 * DENORM_MIN1 \
+ : fn (3.0##L1 * DENORM_MIN1, DENORM_MIN2); \
CHECK (r == 2.0##L1 * DENORM_MIN1); \
- const type s = fn (4.0##L1 * DENORM_MIN1, 2.0##L2 * DENORM_MIN2); \
+ const type s \
+ = (NEED_EXC || NEED_ERRNO) ? 3.0##L1 * DENORM_MIN1 \
+ : fn (4.0##L1 * DENORM_MIN1, 2.0##L2 * DENORM_MIN2); \
CHECK (s == 3.0##L1 * DENORM_MIN1); \
- const type t = fn (MIN1, 0.0##L2); \
+ const type t \
+ = (NEED_EXC || NEED_ERRNO) ? MIN1 - DENORM_MIN1 \
+ : fn (MIN1, 0.0##L2); \
CHECK (t == MIN1 - DENORM_MIN1); \
- const type u = fn (MIN1 - DENORM_MIN1, -MIN2); \
+ const type u \
+ = (NEED_EXC || NEED_ERRNO) ? MIN1 - 2.0##L1 * DENORM_MIN1 \
+ : fn (MIN1 - DENORM_MIN1, -MIN2);
\
CHECK (u == MIN1 - 2.0##L1 * DENORM_MIN1); \
- const type v = fn (MIN1 - 2.0##L1 * DENORM_MIN1, 100.0##L2); \
+ const type v \
+ = (NEED_EXC || NEED_ERRNO) ? MIN1 - DENORM_MIN1 \
+ : fn (MIN1 - 2.0##L1 * DENORM_MIN1, 100.0##L2); \
CHECK (v == MIN1 - DENORM_MIN1); \
const type w = fn (MIN1 - DENORM_MIN1, MAX2);
\
CHECK (w == MIN1); \
@@ -82,9 +100,13 @@ name (void)
\
CHECK (x == MIN1 + DENORM_MIN1); \
const type y = fn (MIN1 + DENORM_MIN1, __builtin_inf##l2 ());
\
CHECK (y == MIN1 + 2.0##L1 * DENORM_MIN1); \
- const type z = fn (MIN1 / 2.0##L1, -MIN2); \
+ const type z \
+ = (NEED_EXC || NEED_ERRNO) ? MIN1 / 2.0##L1 - DENORM_MIN1 \
+ : fn (MIN1 / 2.0##L1, -MIN2); \
CHECK (z == MIN1 / 2.0##L1 - DENORM_MIN1); \
- const type aa = fn (-MIN1 / 4.0##L1, MIN2); \
+ const type aa
\
+ = (NEED_EXC || NEED_ERRNO) ? -MIN1 / 4.0##L1 + DENORM_MIN1 \
+ : fn (-MIN1 / 4.0##L1, MIN2); \
CHECK (aa == -MIN1 / 4.0##L1 + DENORM_MIN1); \
const type ab = fn (MIN1 * 2.0##L1, -MIN2); \
CHECK (ab == MIN1 * 2.0##L1 - DENORM_MIN1); \
@@ -92,9 +114,13 @@ name (void)
\
CHECK (ac == MIN1 * 4.0##L1 - DENORM_MIN1 * 2.0##L1);
\
const type ad = fn (MIN1 * 64.0##L1, MIN2); \
CHECK (ad == MIN1 * 64.0##L1 - DENORM_MIN1 * 32.0##L1); \
- const type ae = fn (MIN1 / 2.0##L1 - DENORM_MIN1, 100.0##L2);
\
+ const type ae
\
+ = (NEED_EXC || NEED_ERRNO) ? MIN1 / 2.0##L1
\
+ : fn (MIN1 / 2.0##L1 - DENORM_MIN1, 100.0##L2); \
CHECK (ae == MIN1 / 2.0##L1);
\
- const type af = fn (-MIN1 / 4 + DENORM_MIN1, -100.0##L2); \
+ const type af
\
+ = (NEED_EXC || NEED_ERRNO) ? -MIN1 / 4.0##L1 \
+ : fn (-MIN1 / 4 + DENORM_MIN1, -100.0##L2); \
CHECK (af == -MIN1 / 4.0##L1); \
const type ag = fn (MIN1 * 2.0##L1 - DENORM_MIN1, 100.0##L2);
\
CHECK (ag == MIN1 * 2.0##L1);
\
Jakub
