Re: [PATCH] Builtin function roundeven folding implementation

[Martin Jambor <mjambor@suse.cz>]

Hi Joseph,

can you please have look at this patch from Tejas, whether it is perhaps
ready to be committed to trunk or what things still need to be
addressed?

Thanks a lot,

Martin



On Fri, Jun 28 2019, Tejas Joshi wrote:
> Hi.
> This patch includes implementation of new function roundeven along
> with two utility functions. The patch bootstraps on x86_64-linux-gnu
> and passes regression tests.
>
> Thanks,
> Tejas
>
> gcc/ChangeLog:
>
> 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 function
>     call and fold_const_conversion call for roundeven function.
>     * 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.
> diff --git a/gcc/builtins.c b/gcc/builtins.c
> index 3463ffb1539..85a945877a4 100644
> --- a/gcc/builtins.c
> +++ b/gcc/builtins.c
> @@ -2085,6 +2085,7 @@ 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..d9b546e6803 100644
> --- a/gcc/fold-const-call.c
> +++ b/gcc/fold-const-call.c
> @@ -836,6 +836,15 @@ fold_const_call_ss (real_value *result, combined_fn fn,
>  	}
>        return false;
>  
> +    CASE_CFN_ROUNDEVEN:
> +    CASE_CFN_ROUNDEVEN_FN:
> +      if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
> +  {
> +    real_roundeven (result, format, arg);
> +    return true;
> +  }
> +      return false;
> +
>      CASE_CFN_LOGB:
>        return fold_const_logb (result, arg, format);
>  
> @@ -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);
> +
>      CASE_CFN_IRINT:
>      CASE_CFN_LRINT:
>      CASE_CFN_LLRINT:
> 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..ab71430709f 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..76889bff0ea 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