On Sat, 21 Apr 2018, Jakub Jelinek wrote:
> Hi!
>
> This patch adds constant folding for next{after,toward}{,f,l}.
> It doesn't handle decimal (we don't have a builtins that would need it),
> nor composite modes (IBM double double; nextafter/nexttoward for variable
> precision types isn't really well defined; we handle nexttoward where long
> double is IBM double double) and for now punts also on formats without
> denormals or infinities (don't really know what the library nextafter does
> for those).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for stage1?
>
> 2018-04-21 Jakub Jelinek <[email protected]>
>
> PR libstdc++/85466
> * real.h (real_nextafter): Declare.
> * real.c (real_nextafter): New function.
> * fold-const-call.c (fold_const_nextafter): New function.
> (fold_const_call_sss): Call it for CASE_CFN_NEXTAFTER and
> CASE_CFN_NEXTTOWARD.
> (fold_const_call_1): For CASE_CFN_NEXTTOWARD call fold_const_call_sss
> even when arg1_mode is different from arg0_mode.
>
> * gcc.dg/nextafter-1.c: New test.
> * gcc.dg/nextafter-2.c: New test.
> * gcc.dg/nextafter-3.c: New test.
> * gcc.dg/nextafter-4.c: New test.
>
> --- gcc/real.h.jj 2018-01-03 10:19:54.349533828 +0100
> +++ gcc/real.h 2018-04-20 12:44:30.707350855 +0200
> @@ -507,6 +507,10 @@ extern void real_copysign (REAL_VALUE_TY
> extern bool real_isinteger (const REAL_VALUE_TYPE *, format_helper);
> extern bool real_isinteger (const REAL_VALUE_TYPE *, HOST_WIDE_INT *);
>
> +/* Calculate nextafter (X, Y) in format FMT. */
> +extern bool real_nextafter (REAL_VALUE_TYPE *, format_helper,
> + const REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *);
> +
> /* Write into BUF the maximum representable finite floating-point
> number, (1 - b**-p) * b**emax for a given FP format FMT as a hex
> float string. BUF must be large enough to contain the result. */
> --- gcc/real.c.jj 2018-01-03 10:19:55.003533933 +0100
> +++ gcc/real.c 2018-04-21 19:29:09.103584254 +0200
> @@ -5048,6 +5048,102 @@ real_isinteger (const REAL_VALUE_TYPE *c
> return false;
> }
>
> +/* Calculate nextafter (X, Y) or nexttoward (X, Y). Return true if
> + underflow or overflow needs to be raised. */
> +
> +bool
> +real_nextafter (REAL_VALUE_TYPE *r, format_helper fmt,
> + const REAL_VALUE_TYPE *x, const REAL_VALUE_TYPE *y)
> +{
> + int cmp = do_compare (x, y, 2);
> + /* If either operand is NaN, return qNaN. */
> + if (cmp == 2)
> + {
> + get_canonical_qnan (r, 0);
> + return false;
> + }
> + /* If x == y, return y cast to target type. */
> + if (cmp == 0)
> + {
> + real_convert (r, fmt, y);
> + return false;
> + }
> +
> + if (x->cl == rvc_zero)
> + {
> + get_zero (r, y->sign);
> + r->cl = rvc_normal;
> + SET_REAL_EXP (r, fmt->emin - fmt->p + 1);
> + r->sig[SIGSZ - 1] = SIG_MSB;
> + return false;
> + }
> +
> + int np2 = SIGNIFICAND_BITS - fmt->p;
> + /* For denormals adjust np2 correspondingly. */
> + if (x->cl == rvc_normal && REAL_EXP (x) < fmt->emin)
> + np2 += fmt->emin - REAL_EXP (x);
> +
> + REAL_VALUE_TYPE u;
> + get_zero (r, x->sign);
> + get_zero (&u, 0);
> + set_significand_bit (&u, np2);
> + r->cl = rvc_normal;
> + SET_REAL_EXP (r, REAL_EXP (x));
> +
> + if (x->cl == rvc_inf)
> + {
> + bool borrow = sub_significands (r, r, &u, 0);
> + gcc_assert (borrow);
> + SET_REAL_EXP (r, fmt->emax);
> + }
> + else if (cmp == (x->sign ? 1 : -1))
> + {
> + if (add_significands (r, x, &u))
> + {
> + /* Overflow. Means the significand had been all ones, and
> + is now all zeros. Need to increase the exponent, and
> + possibly re-normalize it. */
> + SET_REAL_EXP (r, REAL_EXP (r) + 1);
> + if (REAL_EXP (r) > fmt->emax)
> + {
> + get_inf (r, x->sign);
> + return true;
> + }
> + r->sig[SIGSZ - 1] = SIG_MSB;
> + }
> + }
> + else
> + {
> + if (REAL_EXP (x) > fmt->emin && x->sig[SIGSZ - 1] == SIG_MSB)
> + {
> + int i;
> + for (i = SIGSZ - 2; i >= 0; i--)
> + if (x->sig[i])
> + break;
> + if (i < 0)
> + {
> + /* When mantissa is 1.0, we need to subtract only
> + half of u: nextafter (1.0, 0.0) is 1.0 - __DBL_EPSILON__ / 2
> + rather than 1.0 - __DBL_EPSILON__. */
> + clear_significand_bit (&u, np2);
> + np2--;
> + set_significand_bit (&u, np2);
> + }
> + }
> + sub_significands (r, x, &u, 0);
> + }
> +
> + /* Clear out trailing garbage. */
> + clear_significand_below (r, np2);
> + normalize (r);
> + if (REAL_EXP (r) <= fmt->emin - fmt->p)
> + {
> + get_zero (r, x->sign);
> + return true;
> + }
> + return r->cl == rvc_zero;
> +}
> +
> /* Write into BUF the maximum representable finite floating-point
> number, (1 - b**-p) * b**emax for a given FP format FMT as a hex
> float string. LEN is the size of BUF, and the buffer must be large
> --- gcc/fold-const-call.c.jj 2018-01-14 17:16:52.873836266 +0100
> +++ gcc/fold-const-call.c 2018-04-20 19:36:40.987942433 +0200
> @@ -529,6 +529,49 @@ fold_const_pow (real_value *result, cons
>
> /* Try to evaluate:
>
> + *RESULT = nextafter (*ARG0, *ARG1)
> +
> + or
> +
> + *RESULT = nexttoward (*ARG0, *ARG1)
> +
> + in format FORMAT. Return true on success. */
> +
> +static bool
> +fold_const_nextafter (real_value *result, const real_value *arg0,
> + const real_value *arg1, const real_format *format)
> +{
> + if (flag_signaling_nans
HONOR_SNANS ()?
> + && (REAL_VALUE_ISSIGNALING_NAN (*arg0)
> + || REAL_VALUE_ISSIGNALING_NAN (*arg1)))
> + return false;
> +
> + /* Don't handle composite modes, nor decimal, nor modes without
> + inf or denorm at least for now. */
> + if (format->pnan < format->p
> + || format->b == 10
> + || !format->has_inf
> + || !format->has_denorm)
> + return false;
I wonder if we should assert in real_nextafter that we can actually
handle the input? It likely returns garbage if fed with decimal float
stuff?
Otherwise looks OK.
Thanks,
Richard.
> + if (real_nextafter (result, format, arg0, arg1)
> + /* If raising underflow or overflow and setting errno to ERANGE,
> + fail if we care about those side-effects. */
> + && (flag_trapping_math || flag_errno_math))
> + return false;
> + /* Similarly for nextafter (0, 1) raising underflow. */
> + else if (flag_trapping_math
> + && arg0->cl == rvc_zero
> + && result->cl != rvc_zero)
> + return false;
> +
> + real_convert (result, format, result);
> +
> + return true;
> +}
> +
> +/* Try to evaluate:
> +
> *RESULT = ldexp (*ARG0, ARG1)
>
> in format FORMAT. Return true on success. */
> @@ -1260,6 +1303,10 @@ fold_const_call_sss (real_value *result,
> CASE_CFN_POW:
> return fold_const_pow (result, arg0, arg1, format);
>
> + CASE_CFN_NEXTAFTER:
> + CASE_CFN_NEXTTOWARD:
> + return fold_const_nextafter (result, arg0, arg1, format);
> +
> default:
> return false;
> }
> @@ -1365,20 +1412,33 @@ fold_const_call_1 (combined_fn fn, tree
> machine_mode arg0_mode = TYPE_MODE (TREE_TYPE (arg0));
> machine_mode arg1_mode = TYPE_MODE (TREE_TYPE (arg1));
>
> - if (arg0_mode == arg1_mode
> + if (mode == arg0_mode
> && real_cst_p (arg0)
> && real_cst_p (arg1))
> {
> gcc_checking_assert (SCALAR_FLOAT_MODE_P (arg0_mode));
> - if (mode == arg0_mode)
> + REAL_VALUE_TYPE result;
> + if (arg0_mode == arg1_mode)
> {
> /* real, real -> real. */
> - REAL_VALUE_TYPE result;
> if (fold_const_call_sss (&result, fn, TREE_REAL_CST_PTR (arg0),
> TREE_REAL_CST_PTR (arg1),
> REAL_MODE_FORMAT (mode)))
> return build_real (type, result);
> }
> + else if (arg1_mode == TYPE_MODE (long_double_type_node))
> + switch (fn)
> + {
> + CASE_CFN_NEXTTOWARD:
> + /* real, long double -> real. */
> + if (fold_const_call_sss (&result, fn, TREE_REAL_CST_PTR (arg0),
> + TREE_REAL_CST_PTR (arg1),
> + REAL_MODE_FORMAT (mode)))
> + return build_real (type, result);
> + break;
> + default:
> + break;
> + }
> return NULL_TREE;
> }
>
> --- gcc/testsuite/gcc.dg/nextafter-1.c.jj 2018-04-20 20:53:15.418133039
> +0200
> +++ gcc/testsuite/gcc.dg/nextafter-1.c 2018-04-20 20:59:27.598468003
> +0200
> @@ -0,0 +1,159 @@
> +/* PR libstdc++/85466 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fno-math-errno -fno-trapping-math
> -fdump-tree-optimized" } */
> +/* { dg-add-options ieee } */
> +/* { dg-final { scan-tree-dump-not "nextafter" "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "nexttoward" "optimized" } } */
> +
> +float nextafterf (float, float);
> +double nextafter (double, double);
> +long double nextafterl (long double, long double);
> +float nexttowardf (float, long double);
> +double nexttoward (double, long double);
> +long double nexttowardl (long double, long double);
> +
> +#define CHECK(x) if (!(x)) __builtin_abort ()
> +
> +#ifndef NEED_ERRNO
> +#define NEED_ERRNO 0
> +#endif
> +#ifndef NEED_EXC
> +#define NEED_EXC 0
> +#endif
> +
> +#define TEST(name, fn, type, L1, L2, l1, l2, MIN1, \
> + MAX1, DENORM_MIN1, EPSILON1, MIN2, MAX2, DENORM_MIN2) \
> +void \
> +name (void) \
> +{ \
> + const type a = fn (0.0##L1, 0.0##L2);
> \
> + CHECK (a == 0.0##L1 && !__builtin_signbit (a)); \
> + const type b = fn (0.0##L1, -0.0##L2); \
> + CHECK (b == 0.0##L1 && __builtin_signbit (b)); \
> + const type c = fn (__builtin_nan##l1 (""), 0.0##L2);
> \
> + CHECK (__builtin_isnan##l1 (c)); \
> + const type d = fn (2.0##L1, __builtin_nan##l2 (""));
> \
> + CHECK (__builtin_isnan##l1 (d)); \
> + const type e = NEED_EXC ? DENORM_MIN1 : fn (0.0##L1, 8.0##L2); \
> + CHECK (e == DENORM_MIN1); \
> + const type f = fn (1.0##L1, 8.0##L2);
> \
> + CHECK (f == 1.0##L1 + EPSILON1); \
> + const type g = fn (1.0##L1, -8.0##L2); \
> + CHECK (g == 1.0##L1 - EPSILON1 / 2.0##L1); \
> + const type h = fn (__builtin_inf (), 0.0##L2); \
> + CHECK (h == MAX1); \
> + const type i = fn (-1.0##L1, -__builtin_inf ()); \
> + CHECK (i == -1.0##L1 - EPSILON1); \
> + const type j = fn (1.5##L1, __builtin_inf ()); \
> + CHECK (j == 1.5##L1 + EPSILON1); \
> + const type k = fn (1.5##L1 - EPSILON1, 100.0##L2); \
> + CHECK (k == 1.5##L1);
> \
> + const type l
> \
> + = (NEED_EXC || NEED_ERRNO) ? 0.0##L1 : fn (DENORM_MIN1, 0.0##L2);
> \
> + CHECK (l == 0.0##L1 && !__builtin_signbit (l)); \
> + const type m
> \
> + = (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); \
> + CHECK (n == 2.0##L1 * DENORM_MIN1);
> \
> + const type o = fn (n, 24.0##L2); \
> + CHECK (o == 3.0##L1 * DENORM_MIN1);
> \
> + const type p = fn (o, 132.0##L2); \
> + CHECK (p == 4.0##L1 * DENORM_MIN1);
> \
> + const type q = fn (2.0##L1 * DENORM_MIN1, -__builtin_inf ());
> \
> + CHECK (q == DENORM_MIN1); \
> + const type r = 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); \
> + CHECK (s == 3.0##L1 * DENORM_MIN1);
> \
> + const type t = fn (MIN1, 0.0##L2); \
> + CHECK (t == MIN1 - DENORM_MIN1); \
> + const type u = 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);
> \
> + CHECK (v == MIN1 - DENORM_MIN1); \
> + const type w = fn (MIN1 - DENORM_MIN1, MAX2);
> \
> + CHECK (w == MIN1); \
> + const type x = fn (MIN1, 17.0##L2);
> \
> + 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); \
> + CHECK (z == MIN1 / 2.0##L1 - DENORM_MIN1); \
> + const type aa = 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);
> \
> + const type ac = fn (MIN1 * 4.0##L1, MIN2); \
> + 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);
> \
> + CHECK (ae == MIN1 / 2.0##L1);
> \
> + const type af = 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);
> \
> + const type ah = fn (MIN1 * 4.0##L1 - 2.0##L1 * DENORM_MIN1, 100.0##L2);
> \
> + CHECK (ah == MIN1 * 4.0##L1);
> \
> + const type ai = fn (MIN1 * 64.0##L1 - 32.0##L1 * DENORM_MIN1, 100.0##L2);
> \
> + CHECK (ai == MIN1 * 64.0##L1); \
> + const type aj = fn (MIN1 * 64.0##L1, 100.0##L2); \
> + CHECK (aj == MIN1 * 64.0##L1 + 64.0##L1 * DENORM_MIN1); \
> + const type ak = fn (MIN1 * 64.0##L1 + DENORM_MIN1 * 64.0##L1, 1024.0##L2);
> \
> + CHECK (ak == MIN1 * 64.0##L1 + 128.0##L1 * DENORM_MIN1); \
> + const type al = fn (128.0##L1, 128.0##L2); \
> + CHECK (al == 128.0##L1); \
> + const type am = fn (128.0##L1, 129.0##L2); \
> + CHECK (am == 128.0##L1 + 128.0##L1 * EPSILON1); \
> + const type an = fn (-128.0##L1 + -128.0##L1 * EPSILON1, -130.0##L2);
> \
> + CHECK (an == -128.0##L1 - 256.0##L1 * EPSILON1); \
> + const type ao = fn (128.0##L1 + 256.0##L1 * EPSILON1, 256.0##L2); \
> + CHECK (ao == 128.0##L1 + 384.0##L1 * EPSILON1); \
> + const type ap = fn (128.0##L1 + 384.0##L1 * EPSILON1, -0.0##L2); \
> + CHECK (ap == 128.0##L1 + 256.0##L1 * EPSILON1); \
> + const type aq = fn (128.0##L1 + 256.0##L1 * EPSILON1, 1.0##L2); \
> + CHECK (aq == 128.0##L1 + 128.0##L1 * EPSILON1); \
> + const type ar = fn (128.0##L1 + 128.0##L1 * EPSILON1, 0.0##L2); \
> + CHECK (ar == 128.0##L1); \
> + const type as = fn (128.0##L1, 0.0##L2); \
> + CHECK (as == 128.0##L1 - 64.0##L1 * EPSILON1); \
> + const type at = fn (128.0##L1 - 64.0##L1 * EPSILON1, 5.0##L2); \
> + CHECK (at == 128.0##L1 - 128.0##L1 * EPSILON1); \
> +}
> +
> +TEST (test1, nextafterf, float, F, F, f, f, __FLT_MIN__, __FLT_MAX__,
> + __FLT_DENORM_MIN__, __FLT_EPSILON__, __FLT_MIN__, __FLT_MAX__,
> + __FLT_DENORM_MIN__)
> +TEST (test2, nextafter, double, , , , , __DBL_MIN__, __DBL_MAX__,
> + __DBL_DENORM_MIN__, __DBL_EPSILON__, __DBL_MIN__, __DBL_MAX__,
> + __DBL_DENORM_MIN__)
> +#if __LDBL_MANT_DIG__ != 106
> +TEST (test3, nextafterl, long double, L, L, l, l, __LDBL_MIN__, __LDBL_MAX__,
> + __LDBL_DENORM_MIN__, __LDBL_EPSILON__, __LDBL_MIN__, __LDBL_MAX__,
> + __LDBL_DENORM_MIN__)
> +TEST (test4, nexttowardf, float, F, L, f, l, __FLT_MIN__, __FLT_MAX__,
> + __FLT_DENORM_MIN__, __FLT_EPSILON__, __LDBL_MIN__, __LDBL_MAX__,
> + __LDBL_DENORM_MIN__)
> +TEST (test5, nexttoward, double, , L, , l, __DBL_MIN__, __DBL_MAX__,
> + __DBL_DENORM_MIN__, __DBL_EPSILON__, __LDBL_MIN__, __LDBL_MAX__,
> + __LDBL_DENORM_MIN__)
> +TEST (test6, nexttowardl, long double, L, L, l, l, __LDBL_MIN__,
> __LDBL_MAX__,
> + __LDBL_DENORM_MIN__, __LDBL_EPSILON__, __LDBL_MIN__, __LDBL_MAX__,
> + __LDBL_DENORM_MIN__)
> +#endif
> +
> +int
> +main ()
> +{
> + test1 ();
> + test2 ();
> +#if __LDBL_MANT_DIG__ != 106
> + test3 ();
> + test4 ();
> + test5 ();
> + test6 ();
> +#endif
> + return 0;
> +}
> --- gcc/testsuite/gcc.dg/nextafter-2.c.jj 2018-04-20 20:53:24.662141363
> +0200
> +++ gcc/testsuite/gcc.dg/nextafter-2.c 2018-04-20 20:54:01.031174134
> +0200
> @@ -0,0 +1,6 @@
> +/* PR libstdc++/85466 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fno-builtin" } */
> +/* { dg-add-options ieee } */
> +
> +#include "nextafter-1.c"
> --- gcc/testsuite/gcc.dg/nextafter-3.c.jj 2018-04-20 20:54:09.867182101
> +0200
> +++ gcc/testsuite/gcc.dg/nextafter-3.c 2018-04-20 20:59:48.280486574
> +0200
> @@ -0,0 +1,9 @@
> +/* PR libstdc++/85466 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fmath-errno -fno-trapping-math -fdump-tree-optimized"
> } */
> +/* { dg-add-options ieee } */
> +/* { dg-final { scan-tree-dump-not "nextafter" "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "nexttoward" "optimized" } } */
> +
> +#define NEED_ERRNO 1
> +#include "nextafter-1.c"
> --- gcc/testsuite/gcc.dg/nextafter-4.c.jj 2018-04-20 20:55:11.880237977
> +0200
> +++ gcc/testsuite/gcc.dg/nextafter-4.c 2018-04-20 20:59:54.927492541
> +0200
> @@ -0,0 +1,10 @@
> +/* PR libstdc++/85466 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fmath-errno -ftrapping-math -fdump-tree-optimized" } */
> +/* { dg-add-options ieee } */
> +/* { dg-final { scan-tree-dump-not "nextafter" "optimized" } } */
> +/* { dg-final { scan-tree-dump-not "nexttoward" "optimized" } } */
> +
> +#define NEED_ERRNO 1
> +#define NEED_EXC 1
> +#include "nextafter-1.c"
>
> Jakub
>
>
--
Richard Biener <[email protected]>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
