Re: About GSOC.

[Tejas Joshi <tejasjoshi9673 at gmail dot com>]

Thanks.
> Did you add an entry for roundeven in builtins.def ?
Yes, I did.

Find here the attached patch.diff for which I did the changes to
implement roundeven. There might be some unnecessary changes and some
necessary changes which have not been made.

Regards,
-Tejas

On Mon, 4 Feb 2019 at 20:36, Prathamesh Kulkarni
<prathamesh.kulkarni@linaro.org> wrote:
>
> On Mon, 4 Feb 2019 at 20:10, Tejas Joshi <tejasjoshi9673@gmail.com> wrote:
> >
> > Hello.
> > I have implemented roundeven function in real.c as follows: (and
> > respective changes in real.h)
> It's a better idea to include all changes in patch instead of copy-pasting.
> Use the command:
> git diff > patch.diff
> which will create a file called "patch.diff" containing the changes
> and send it as an attachment.
> >
> > /* Round X to nearest even integer towards zero. */
> >
> > void
> > real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt,
> >         const REAL_VALUE_TYPE *x)
> > {
> >   REAL_VALUE_TYPE t;
> >
> >   do_fix_trunc (&t, x);
> >   HOST_WIDE_INT i = real_to_integer (&t);
> >   if(i % 2)
> >     do_add (r, &t, &dconstm1, 0);
> >   else
> >     *r = t;
> > }
> >
> > Although I cant get it to test like
> >
> > int foo()
> > {
> >     double x = __builtin_roundeven (3.5);
> >     printf("%f",x);
> >     return (int) x;
> > }
> > Because I do not know its dependencies through other files. I tried to
> > track them down by inspecting real_ceil function, but it also includes
> > other optimization procedures like folding. How do I know enough
> > declarations to be made in respective files?
> Did you add an entry for roundeven in builtins.def ?
>
> Thanks,
> Prathamesh
> >
> > Thanks.
> > -Tejas
> >
> > On Mon, 28 Jan 2019 at 22:33, Tejas Joshi <tejasjoshi9673@gmail.com> wrote:
> > >
> > > Hello.
> > > Representations of real numbers in real.c are a little complex to
> > > understand right now for me. I am still trying to understand them and
> > > figure them out using gdb and cscope. Though conventions are given in
> > > comments in real.c, I will still be trying to figure it out. The
> > > equation and its bitwise representation is not pretty elaborated in
> > > any documentation I could find.
> > >
> > > x = s * b^e * \sum_{k=1}^p f_k * b^{-k}
> > >
> > >     where
> > >         s = sign (+- 1)
> > >         b = base or radix, here always 2
> > >         e = exponent
> > >         p = precision (the number of base-b digits in the significand)
> > >         f_k = the digits of the significand.
> > >
> > > In mean time, I've tried real_round function to work like roundeven. I
> > > will try to submit a clean patch along with roundeven implemented
> > > separately with changes like in builtins.def, adding cases, etc.
> > >
> > > void
> > > real_round (REAL_VALUE_TYPE *r, format_helper fmt,
> > >         const REAL_VALUE_TYPE *x)
> > > {
> > > #if 0
> > >   do_add (r, x, &dconsthalf, x->sign);
> > >   do_fix_trunc (r, r);
> > >   if (fmt)
> > >     real_convert (r, fmt, r);
> > > #endif
> > >   fprintf (stderr, "\nhere\n");
> > >   real_value z;
> > >   do_fix_trunc (&z, x);
> > >   HOST_WIDE_INT i = real_to_integer (&z);
> > >   fprintf (stderr, "\n i = %ld\n", i);
> > >   if (i % 2)
> > >     do_add (r, &z, &dconstm1, 0);
> > >   else
> > >     *r = z;
> > > }
> > >
> > > Thanks.
> > > -Tejas
> > >
> > > On Sat, 26 Jan 2019 at 03:02, Joseph Myers <joseph@codesourcery.com> wrote:
> > > >
> > > > On Sat, 26 Jan 2019, Tejas Joshi wrote:
> > > >
> > > > > function with byte-byte comparison which also include mpfr. (Correct
> > > > > me if I am wrong.) What is the significance of mpfr related to these
> > > > > internal representations?
> > > >
> > > > real.c provides a fixed-size representation of floating-point numbers that
> > > > allows for various non-IEEE formats supported by GCC, and also allows
> > > > functions from dfp.c to be used for decimal floating-point formats.
> > > >
> > > > MPFR is used in GCC to provide operations that are nontrivial to
> > > > implement, especially those that are nontrivial to implement in such a
> > > > fixed-size context.  real.c operations wrap around MPFR ones where
> > > > appropriate, doing whatever's needed in cases where there are non-IEEE
> > > > semantics or sets of values.
> > > >
> > > > --
> > > > Joseph S. Myers
> > > > joseph@codesourcery.com

diff --git a/gcc/builtins.c b/gcc/builtins.c
index 25e01e4092b..25282d2122d 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -2067,6 +2067,7 @@ mathfn_built_in_2 (tree type, combined_fn fn)
     CASE_MATHFN (REMQUO)
     CASE_MATHFN_FLOATN (RINT)
     CASE_MATHFN_FLOATN (ROUND)
+    CASE_MATHFN_FLOATN (ROUNDEVEN)
     CASE_MATHFN (SCALB)
     CASE_MATHFN (SCALBLN)
     CASE_MATHFN (SCALBN)
diff --git a/gcc/builtins.def b/gcc/builtins.def
index ef89729fd0c..f1b6830a49c 100644
--- a/gcc/builtins.def
+++ b/gcc/builtins.def
@@ -308,6 +308,7 @@ DEF_C99_BUILTIN        (BUILT_IN_CBRT, "cbrt", BT_FN_DOUBLE_DOUBLE, ATTR_MATHFN_
 DEF_C99_BUILTIN        (BUILT_IN_CBRTF, "cbrtf", BT_FN_FLOAT_FLOAT, ATTR_MATHFN_FPROUNDING)
 DEF_C99_BUILTIN        (BUILT_IN_CBRTL, "cbrtl", BT_FN_LONGDOUBLE_LONGDOUBLE, ATTR_MATHFN_FPROUNDING)
 DEF_LIB_BUILTIN        (BUILT_IN_CEIL, "ceil", BT_FN_DOUBLE_DOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
+DEF_EXT_LIB_BUILTIN    (BUILT_IN_ROUNDEVEN, "roundeven", BT_FN_DOUBLE_DOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
 DEF_C99_C90RES_BUILTIN (BUILT_IN_CEILF, "ceilf", BT_FN_FLOAT_FLOAT, ATTR_CONST_NOTHROW_LEAF_LIST)
 DEF_C99_C90RES_BUILTIN (BUILT_IN_CEILL, "ceill", BT_FN_LONGDOUBLE_LONGDOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
 #define CEIL_TYPE(F) BT_FN_##F##_##F
diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index cda314e1121..b89918815f9 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -224,6 +224,7 @@ DEF_INTERNAL_FLT_FLOATN_FN (FLOOR, ECF_CONST, floor, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (NEARBYINT, ECF_CONST, nearbyint, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (RINT, ECF_CONST, rint, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (ROUND, ECF_CONST, round, unary)
+DEF_INTERNAL_FLT_FLOATN_FN (ROUNDEVEN, ECF_CONST, roundeven, unary)
 DEF_INTERNAL_FLT_FLOATN_FN (TRUNC, ECF_CONST, btrunc, unary)
 
 /* Binary math functions.  */
diff --git a/gcc/optabs.def b/gcc/optabs.def
index 5a67f5eed5e..eb9e22acd8f 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -267,6 +267,7 @@ OPTAB_D (fnms_optab, "fnms$a4")
 
 OPTAB_D (rint_optab, "rint$a2")
 OPTAB_D (round_optab, "round$a2")
+OPTAB_D (roundeven_optab, "roundeven$a2")
 OPTAB_D (floor_optab, "floor$a2")
 OPTAB_D (ceil_optab, "ceil$a2")
 OPTAB_D (btrunc_optab, "btrunc$a2")
diff --git a/gcc/real.c b/gcc/real.c
index f822ae82d61..9c57f50e8fc 100644
--- a/gcc/real.c
+++ b/gcc/real.c
@@ -5004,10 +5006,39 @@ void
+/* Round X to nearest even integer towards zero. */
+
+void
+real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt,
+		const REAL_VALUE_TYPE *x)
+{
+  REAL_VALUE_TYPE t;
+
+  do_fix_trunc (&t, x);
+  HOST_WIDE_INT i = real_to_integer (&t);
+  fprintf (stderr, "\nhere\n");
+  fprintf (stderr, "\n i = %ld\n", i);
+  if(i % 2)
+    do_add (r, &t, &dconstm1, 0);
+  else
+    *r = t;
 }
 
 /* Set the sign of R to the sign of X.  */
diff --git a/gcc/real.h b/gcc/real.h
index 0ce42565708..10898eae79e 100644
--- a/gcc/real.h
+++ b/gcc/real.h
@@ -499,6 +499,8 @@ 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 *);