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Re: [PATCH] Builtin function roundeven folding implementation
Hi Tejas,
On Wed, Aug 14 2019, Tejas Joshi wrote:
> Hi.
> Here is a clean patch that does not fold roundeven resulting for
> integer type and the conditions for folding functions
> round/ceil/floor/roundeven and trunc only checks for signaling NaN.
wouldn't checking for *signalling* NaNs mean using the macro
REAL_VALUE_ISSIGNALING_NAN rather than REAL_VALUE_ISNAN?
Joseph, would fixing this make the patch good to go? Tejas's GSoC
project results would look much better if we could get this and the
(already approved) follow-up patch committed by the end of the week.
Thanks a lot,
Martin
> 2019-06-12 Tejas Joshi <tejasjoshi9673@gmail.com>
>
> * builtins.c (mathfn_built_in_2): Added CASE_MATHFN for ROUNDEVEN.
> * builtins.def: Added function definitions for roundeven function
> variants.
> * fold-const-call.c (fold_const_call_ss): Added case for roundeven
> function call.
> * fold-const.c (negate_mathfn_p): Added case for roundeven function.
> (tree_call_nonnegative_warnv_p): Added case for roundeven function.
> (integer_valued_real_call_p): Added case for roundeven function.
> * real.c (is_even): New function. Returns true if real number is
> even, otherwise returns false.
> (is_halfway_below): New function. Returns true if real number is
> halfway between two integers, else return false.
> (real_roundeven): New function. Round real number to nearest
> integer, rounding halfway cases towards even.
> * real.h (real_value): Added descriptive comments.
> Added function declaration for roundeven function.
>
> gcc/testsuite/ChangeLog:
>
> 2019-06-12 Tejas Joshi <tejasjoshi9673@gmail.com>
>
> * gcc.dg/torture/builtin-round-roundeven.c: New test.
> * gcc.dg/torture/builtin-round-roundevenf128.c: New test.
>
> On Sat, 10 Aug 2019 at 02:15, Joseph Myers <joseph@codesourcery.com> wrote:
>>
>> On Fri, 28 Jun 2019, Tejas Joshi wrote:
>>
>> > + CASE_CFN_ROUNDEVEN:
>> > + CASE_CFN_ROUNDEVEN_FN:
>> > + if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
>>
>> Checking flag_errno_math here does not make sense. roundeven never sets
>> errno (at least, TS 18661-1 makes it implementation-defined whether sNaN
>> input counts as a domain error, but I'm not aware of implementations that
>> make it a domain error and set errno, and typically GCC follows glibc in
>> such cases in the absence of known implementations requiring a different
>> approach).
>>
>> The only case where you need to avoid folding is where the argument is a
>> signaling NaN (it's fine to fold for quiet NaNs). In that case, you need
>> to avoid folding to avoid losing an exception (if the user cares about
>> signaling NaNs, they probably care about exceptions) - so it still doesn't
>> matter whether the library implementation also sets errno or not.
>>
>> (Yes, this means the existing ceil / floor / round checks should be
>> adjusted just to check for signaling NaN, though that's fairly cosmetic as
>> calls to those functions with quiet NaN argument still get folded via
>> match.pd. trunc ought also check for signaling NaN rather than folding
>> unconditionally, so all those functions should end up with the same
>> conditions for folding.)
>>
>> > @@ -898,6 +907,10 @@ fold_const_call_ss (wide_int *result, combined_fn fn,
>> > return fold_const_conversion (result, real_round, arg,
>> > precision, format);
>> >
>> > + CASE_CFN_ROUNDEVEN:
>> > + CASE_CFN_ROUNDEVEN_FN:
>> > + return fold_const_conversion (result, real_roundeven, arg, precision, format);
>> > +
>>
>> This is the version of fold_const_call_ss for functions returning a result
>> of integer type; roundeven returns an integer value in a floating-point
>> type. I don't think this code should be there, and I don't think this
>> version of the function should be called at all for roundeven.
>>
>> --
>> Joseph S. Myers
>> joseph@codesourcery.com
> diff --git a/gcc/builtins.c b/gcc/builtins.c
> index e2ba356c0d3..8ceb077b0bf 100644
> --- a/gcc/builtins.c
> +++ b/gcc/builtins.c
> @@ -2056,6 +2056,7 @@ mathfn_built_in_2 (tree type, combined_fn fn)
> CASE_MATHFN (REMQUO)
> CASE_MATHFN_FLOATN (RINT)
> CASE_MATHFN_FLOATN (ROUND)
> + CASE_MATHFN (ROUNDEVEN)
> CASE_MATHFN (SCALB)
> CASE_MATHFN (SCALBLN)
> CASE_MATHFN (SCALBN)
> diff --git a/gcc/builtins.def b/gcc/builtins.def
> index 6d41bdb4f44..8bb7027aac7 100644
> --- a/gcc/builtins.def
> +++ b/gcc/builtins.def
> @@ -542,12 +542,18 @@ DEF_C99_BUILTIN (BUILT_IN_RINTL, "rintl", BT_FN_LONGDOUBLE_LONGDOUBLE, AT
> #define RINT_TYPE(F) BT_FN_##F##_##F
> DEF_EXT_LIB_FLOATN_NX_BUILTINS (BUILT_IN_RINT, "rint", RINT_TYPE, ATTR_CONST_NOTHROW_LEAF_LIST)
> #undef RINT_TYPE
> +DEF_EXT_LIB_BUILTIN (BUILT_IN_ROUNDEVEN, "roundeven", BT_FN_DOUBLE_DOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
> +DEF_EXT_LIB_BUILTIN (BUILT_IN_ROUNDEVENF, "roundevenf", BT_FN_FLOAT_FLOAT, ATTR_CONST_NOTHROW_LEAF_LIST)
> +DEF_EXT_LIB_BUILTIN (BUILT_IN_ROUNDEVENL, "roundevenl", BT_FN_LONGDOUBLE_LONGDOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_C99_BUILTIN (BUILT_IN_ROUND, "round", BT_FN_DOUBLE_DOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_C99_BUILTIN (BUILT_IN_ROUNDF, "roundf", BT_FN_FLOAT_FLOAT, ATTR_CONST_NOTHROW_LEAF_LIST)
> DEF_C99_BUILTIN (BUILT_IN_ROUNDL, "roundl", BT_FN_LONGDOUBLE_LONGDOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
> #define ROUND_TYPE(F) BT_FN_##F##_##F
> DEF_EXT_LIB_FLOATN_NX_BUILTINS (BUILT_IN_ROUND, "round", ROUND_TYPE, ATTR_CONST_NOTHROW_LEAF_LIST)
> #undef ROUND_TYPE
> +#define ROUNDEVEN_TYPE(F) BT_FN_##F##_##F
> +DEF_EXT_LIB_FLOATN_NX_BUILTINS (BUILT_IN_ROUNDEVEN, "roundeven", ROUNDEVEN_TYPE, ATTR_CONST_NOTHROW_LEAF_LIST)
> +#undef ROUNDEVEN_TYPE
> DEF_EXT_LIB_BUILTIN (BUILT_IN_SCALB, "scalb", BT_FN_DOUBLE_DOUBLE_DOUBLE, ATTR_MATHFN_FPROUNDING_ERRNO)
> DEF_EXT_LIB_BUILTIN (BUILT_IN_SCALBF, "scalbf", BT_FN_FLOAT_FLOAT_FLOAT, ATTR_MATHFN_FPROUNDING_ERRNO)
> DEF_EXT_LIB_BUILTIN (BUILT_IN_SCALBL, "scalbl", BT_FN_LONGDOUBLE_LONGDOUBLE_LONGDOUBLE, ATTR_MATHFN_FPROUNDING_ERRNO)
> diff --git a/gcc/fold-const-call.c b/gcc/fold-const-call.c
> index 702c8b4057a..73dfb6980f1 100644
> --- a/gcc/fold-const-call.c
> +++ b/gcc/fold-const-call.c
> @@ -806,7 +806,7 @@ fold_const_call_ss (real_value *result, combined_fn fn,
>
> CASE_CFN_FLOOR:
> CASE_CFN_FLOOR_FN:
> - if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
> + if (!REAL_VALUE_ISNAN (*arg))
> {
> real_floor (result, format, arg);
> return true;
> @@ -815,7 +815,7 @@ fold_const_call_ss (real_value *result, combined_fn fn,
>
> CASE_CFN_CEIL:
> CASE_CFN_CEIL_FN:
> - if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
> + if (!REAL_VALUE_ISNAN (*arg))
> {
> real_ceil (result, format, arg);
> return true;
> @@ -824,18 +824,31 @@ fold_const_call_ss (real_value *result, combined_fn fn,
>
> CASE_CFN_TRUNC:
> CASE_CFN_TRUNC_FN:
> - real_trunc (result, format, arg);
> - return true;
> + if (!REAL_VALUE_ISNAN (*arg))
> + {
> + real_trunc (result, format, arg);
> + return true;
> + }
> + return false;
>
> CASE_CFN_ROUND:
> CASE_CFN_ROUND_FN:
> - if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
> + if (!REAL_VALUE_ISNAN (*arg))
> {
> real_round (result, format, arg);
> return true;
> }
> return false;
>
> + CASE_CFN_ROUNDEVEN:
> + CASE_CFN_ROUNDEVEN_FN:
> + if (!REAL_VALUE_ISNAN (*arg))
> + {
> + real_roundeven (result, format, arg);
> + return true;
> + }
> + return false;
> +
> CASE_CFN_LOGB:
> return fold_const_logb (result, arg, format);
>
> diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> index 0ca472d422f..07d82a17e25 100644
> --- a/gcc/fold-const.c
> +++ b/gcc/fold-const.c
> @@ -329,6 +329,8 @@ negate_mathfn_p (combined_fn fn)
> CASE_CFN_LLROUND:
> CASE_CFN_LROUND:
> CASE_CFN_ROUND:
> + CASE_CFN_ROUNDEVEN:
> + CASE_CFN_ROUNDEVEN_FN:
> CASE_CFN_SIN:
> CASE_CFN_SINH:
> CASE_CFN_TAN:
> @@ -13063,6 +13065,8 @@ tree_call_nonnegative_warnv_p (tree type, combined_fn fn, tree arg0, tree arg1,
> CASE_CFN_RINT_FN:
> CASE_CFN_ROUND:
> CASE_CFN_ROUND_FN:
> + CASE_CFN_ROUNDEVEN:
> + CASE_CFN_ROUNDEVEN_FN:
> CASE_CFN_SCALB:
> CASE_CFN_SCALBLN:
> CASE_CFN_SCALBN:
> @@ -13586,6 +13590,8 @@ integer_valued_real_call_p (combined_fn fn, tree arg0, tree arg1, int depth)
> CASE_CFN_RINT_FN:
> CASE_CFN_ROUND:
> CASE_CFN_ROUND_FN:
> + CASE_CFN_ROUNDEVEN:
> + CASE_CFN_ROUNDEVEN_FN:
> CASE_CFN_TRUNC:
> CASE_CFN_TRUNC_FN:
> return true;
> diff --git a/gcc/real.c b/gcc/real.c
> index 0164f097a53..0c0d8c51fe4 100644
> --- a/gcc/real.c
> +++ b/gcc/real.c
> @@ -5010,6 +5010,89 @@ real_round (REAL_VALUE_TYPE *r, format_helper fmt,
> real_convert (r, fmt, r);
> }
>
> +/* Return true including 0 if integer part of R is even, else return
> + false. The function is not valid for rvc_inf and rvc_nan classes. */
> +
> +bool
> +is_even (REAL_VALUE_TYPE *r)
> +{
> + gcc_assert (r->cl != rvc_inf);
> + gcc_assert (r->cl != rvc_nan);
> +
> + if (r->cl == rvc_zero)
> + return true;
> +
> + /* For (-1,1), number is even. */
> + if (REAL_EXP (r) <= 0)
> + return true;
> +
> + /* Check lowest bit, if not set, return true. */
> + else if (REAL_EXP (r) <= SIGNIFICAND_BITS)
> + {
> + unsigned int n = SIGNIFICAND_BITS - REAL_EXP (r);
> + int w = n / HOST_BITS_PER_LONG;
> +
> + unsigned long num = ((unsigned long)1 << (n % HOST_BITS_PER_LONG));
> +
> + if ((r->sig[w] & num) == 0)
> + return true;
> + }
> +
> + else
> + return true;
> +
> + return false;
> +}
> +
> +/* Return true if R is halfway between two integers, else return
> + false. The function is not valid for rvc_inf and rvc_nan classes. */
> +
> +bool
> +is_halfway_below (const REAL_VALUE_TYPE *r)
> +{
> + gcc_assert (r->cl != rvc_inf);
> + gcc_assert (r->cl != rvc_nan);
> + int i;
> +
> + /* For numbers (-0.5,0) and (0,0.5). */
> + if (REAL_EXP (r) < 0)
> + return false;
> +
> + else if (REAL_EXP (r) < SIGNIFICAND_BITS)
> + {
> + unsigned int n = SIGNIFICAND_BITS - REAL_EXP (r) - 1;
> + int w = n / HOST_BITS_PER_LONG;
> +
> + for (i = 0; i < w; ++i)
> + if (r->sig[i] != 0)
> + return false;
> +
> + unsigned long num = ((unsigned long)1 << (n % HOST_BITS_PER_LONG));
> +
> + if (((r->sig[w] & num) != 0) && ((r->sig[w] & (num-1)) == 0))
> + return true;
> + }
> + return false;
> +}
> +
> +/* Round X to nearest integer, rounding halfway cases towards even. */
> +
> +void
> +real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt,
> + const REAL_VALUE_TYPE *x)
> +{
> + if (is_halfway_below (x))
> + {
> + do_add (r, x, &dconsthalf, x->sign);
> + if (!is_even (r))
> + do_add (r, r, &dconstm1, x->sign);
> + if (fmt)
> + real_convert (r, fmt, r);
> + }
> + else
> + real_round (r, fmt, x);
> +}
> +
> /* Set the sign of R to the sign of X. */
>
> void
> diff --git a/gcc/real.h b/gcc/real.h
> index 95b9db83d24..2f41834ecfd 100644
> --- a/gcc/real.h
> +++ b/gcc/real.h
> @@ -41,11 +41,18 @@ struct GTY(()) real_value {
> sure they're packed together, otherwise REAL_VALUE_TYPE_SIZE will
> be miscomputed. */
> unsigned int /* ENUM_BITFIELD (real_value_class) */ cl : 2;
> + /* 1 if number is decimal floating point. */
> unsigned int decimal : 1;
> + /* 1 if number is negative. */
> unsigned int sign : 1;
> + /* 1 if number is signalling. */
> unsigned int signalling : 1;
> + /* 1 if number is canonical
> + All are generally used for handling cases in real.c. */
> unsigned int canonical : 1;
> + /* unbiased exponent of the number. */
> unsigned int uexp : EXP_BITS;
> + /* significand of the number. */
> unsigned long sig[SIGSZ];
> };
>
> @@ -500,6 +507,8 @@ extern void real_ceil (REAL_VALUE_TYPE *, format_helper,
> const REAL_VALUE_TYPE *);
> extern void real_round (REAL_VALUE_TYPE *, format_helper,
> const REAL_VALUE_TYPE *);
> +extern void real_roundeven (REAL_VALUE_TYPE *, format_helper,
> + const REAL_VALUE_TYPE *);
>
> /* Set the sign of R to the sign of X. */
> extern void real_copysign (REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *);
> diff --git a/gcc/testsuite/gcc.dg/torture/builtin-round-roundeven.c b/gcc/testsuite/gcc.dg/torture/builtin-round-roundeven.c
> new file mode 100644
> index 00000000000..f75adf6ec8a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/torture/builtin-round-roundeven.c
> @@ -0,0 +1,23 @@
> +/* { dg-do link } */
> +
> +extern int link_error (int);
> +
> +#define TEST(FN, VALUE, RESULT) \
> + if (__builtin_##FN (VALUE) != RESULT) link_error (__LINE__);
> +
> +int
> +main (void)
> +{
> + TEST(roundeven, 0, 0);
> + TEST(roundeven, 0.5, 0);
> + TEST(roundeven, -0.5, 0);
> + TEST(roundeven, 6, 6);
> + TEST(roundeven, -8, -8);
> + TEST(roundeven, 2.5, 2);
> + TEST(roundeven, 3.5, 4);
> + TEST(roundeven, -1.5, -2);
> + TEST(roundeven, 3.499, 3);
> + TEST(roundeven, 3.501, 4);
> +
> + return 0;
> +}
> \ No newline at end of file
> diff --git a/gcc/testsuite/gcc.dg/torture/builtin-round-roundevenf128.c b/gcc/testsuite/gcc.dg/torture/builtin-round-roundevenf128.c
> new file mode 100644
> index 00000000000..592bad49623
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/torture/builtin-round-roundevenf128.c
> @@ -0,0 +1,20 @@
> +/* { dg-do link } */
> +/* { dg-add-options float128 } */
> +/* { dg-require-effective-target float128 } */
> +
> +extern int link_error (int);
> +
> +#define TEST(FN, VALUE, RESULT) \
> + if (__builtin_##FN##f128 (VALUE) != RESULT) link_error (__LINE__);
> +
> +int
> +main (void)
> +{
> + TEST(roundeven, (0x1p64+0.5f128), (0x1p64f128));
> + TEST(roundeven, (0x1p63+0.5f128), (0x1p63f128));
> + TEST(roundeven, (0x1p63-0.5f128), (0x1p63f128));
> + TEST(roundeven, (0x1p64-0.5f128), (0x1p64f128));
> + TEST(roundeven, (0x1p64+0.501f128), (0x1p64+1.0f128));
> + TEST(roundeven, (0x1.C00000000000039A5653p1f128), (0x1p2f128))
> + return 0;
> +}
> \ No newline at end of file