* Re: [PATCH] Builtin function roundeven folding implementation [not found] ` <alpine.DEB.2.21.1908221426570.27000@digraph.polyomino.org.uk> @ 2019-08-22 16:28 ` Tejas Joshi 2019-08-22 16:35 ` Joseph Myers [not found] ` <CACMrGjA3UyUYcShruM-tiT=rqBiSLX9cmSVmpX0G6SfOq_r4EQ@mail.gmail.com> 1 sibling, 1 reply; 6+ messages in thread From: Tejas Joshi @ 2019-08-22 16:28 UTC (permalink / raw) To: gcc; +Cc: Martin Jambor, hubicka, joseph > I'm concerned that this would produce +0.0 for an argument of -0.5 (via > -0.5 - 0.5 - -1.0 producing +0.0) when it needs to produce -0.0. Would the following overhaul be acceptable as the condition is specialized for -0.5 and +0.5 only. This seems to solve the problem. I did test the roundeven tests and it passes the tests. void real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt, const REAL_VALUE_TYPE *x) { if (is_halfway_below (x)) { if (REAL_EXP (x) == 0) { *r = *x; clear_significand_below (r, SIGNIFICAND_BITS); } else { 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); } tests: /* { 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); if (__builtin_copysign (1, __builtin_roundeven (-0.5)) != -1) link_error (__LINE__); return 0; } Thanks, Tejas On Thu, 22 Aug 2019 at 20:03, Joseph Myers <joseph@codesourcery.com> wrote: > > On Thu, 22 Aug 2019, Martin Jambor wrote: > > > +/* 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); > > I'm concerned that this would produce +0.0 for an argument of -0.5 (via > -0.5 - 0.5 - -1.0 producing +0.0) when it needs to produce -0.0. > > Note that testcases for the sign of zero results need to check e.g. > !!__builtin_signbit on the result, or the result of calling > __builtin_copysign* to extract the sign of the result, since 0.0 == -0.0 > so checking with ==, while necessary, is not sufficient in that case. > > -- > Joseph S. Myers > joseph@codesourcery.com ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Builtin function roundeven folding implementation 2019-08-22 16:28 ` [PATCH] Builtin function roundeven folding implementation Tejas Joshi @ 2019-08-22 16:35 ` Joseph Myers 2019-08-22 16:56 ` Tejas Joshi 0 siblings, 1 reply; 6+ messages in thread From: Joseph Myers @ 2019-08-22 16:35 UTC (permalink / raw) To: Tejas Joshi; +Cc: gcc, Martin Jambor, hubicka On Thu, 22 Aug 2019, Tejas Joshi wrote: > > I'm concerned that this would produce +0.0 for an argument of -0.5 (via > > -0.5 - 0.5 - -1.0 producing +0.0) when it needs to produce -0.0. > > Would the following overhaul be acceptable as the condition is > specialized for -0.5 and +0.5 only. This seems to solve the problem. I > did test the roundeven tests and it passes the tests. I think that would be reasonable with a comment added to explain that it's ensuring the correct sign of a zero result. > if (__builtin_copysign (1, __builtin_roundeven (-0.5)) != -1) > link_error (__LINE__); I think you should have at least four tests of sign of zero result (arguments -0.5, -0.0, 0.0 and 0.5). Probably also tests of values between +/- 0.5 and 0, e.g. test -0.25 and 0.25 as well. -- Joseph S. Myers joseph@codesourcery.com ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Builtin function roundeven folding implementation 2019-08-22 16:35 ` Joseph Myers @ 2019-08-22 16:56 ` Tejas Joshi 2019-08-22 17:00 ` Joseph Myers 0 siblings, 1 reply; 6+ messages in thread From: Tejas Joshi @ 2019-08-22 16:56 UTC (permalink / raw) To: gcc; +Cc: Martin Jambor, hubicka, joseph > I think you should have at least four tests of sign of zero result > (arguments -0.5, -0.0, 0.0 and 0.5). Probably also tests of values > between +/- 0.5 and 0, e.g. test -0.25 and 0.25 as well. Okay, I have made the following changes and again, the tests pass for roundeven. void real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt, const REAL_VALUE_TYPE *x) { if (is_halfway_below (x)) { /* Special case as -0.5 rounds to -0.0 and similarly +0.5 rounds to +0.0. */ if (REAL_EXP (x) == 0) { *r = *x; clear_significand_below (r, SIGNIFICAND_BITS); } else { 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); } Tests : /* { 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); if (__builtin_copysign (1, __builtin_roundeven (-0.5)) != -1) link_error (__LINE__); if (__builtin_copysign (1, __builtin_roundeven (-0.0)) != -1) link_error (__LINE__); if (__builtin_copysign (-1, __builtin_roundeven (0.5)) != 1) link_error (__LINE__); if (__builtin_copysign (-1, __builtin_roundeven (0.0)) != 1) link_error (__LINE__); if (__builtin_copysign (1, __builtin_roundeven (-0.25)) != -1) link_error (__LINE__); if (__builtin_copysign (-1, __builtin_roundeven (0.25)) != 1) link_error (__LINE__); return 0; } Thanks, Tejas On Thu, 22 Aug 2019 at 22:05, Joseph Myers <joseph@codesourcery.com> wrote: > > On Thu, 22 Aug 2019, Tejas Joshi wrote: > > > > I'm concerned that this would produce +0.0 for an argument of -0.5 (via > > > -0.5 - 0.5 - -1.0 producing +0.0) when it needs to produce -0.0. > > > > Would the following overhaul be acceptable as the condition is > > specialized for -0.5 and +0.5 only. This seems to solve the problem. I > > did test the roundeven tests and it passes the tests. > > I think that would be reasonable with a comment added to explain that it's > ensuring the correct sign of a zero result. > > > if (__builtin_copysign (1, __builtin_roundeven (-0.5)) != -1) > > link_error (__LINE__); > > I think you should have at least four tests of sign of zero result > (arguments -0.5, -0.0, 0.0 and 0.5). Probably also tests of values > between +/- 0.5 and 0, e.g. test -0.25 and 0.25 as well. > > -- > Joseph S. Myers > joseph@codesourcery.com ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Builtin function roundeven folding implementation 2019-08-22 16:56 ` Tejas Joshi @ 2019-08-22 17:00 ` Joseph Myers 0 siblings, 0 replies; 6+ messages in thread From: Joseph Myers @ 2019-08-22 17:00 UTC (permalink / raw) To: Tejas Joshi; +Cc: gcc, Martin Jambor, hubicka On Thu, 22 Aug 2019, Tejas Joshi wrote: > > I think you should have at least four tests of sign of zero result > > (arguments -0.5, -0.0, 0.0 and 0.5). Probably also tests of values > > between +/- 0.5 and 0, e.g. test -0.25 and 0.25 as well. > > Okay, I have made the following changes and again, the tests pass for roundeven. Thanks, I look forward to seeing a full patch with these revisions on gcc-patches. -- Joseph S. Myers joseph@codesourcery.com ^ permalink raw reply [flat|nested] 6+ messages in thread
[parent not found: <CACMrGjA3UyUYcShruM-tiT=rqBiSLX9cmSVmpX0G6SfOq_r4EQ@mail.gmail.com>]
[parent not found: <alpine.DEB.2.21.1908232023080.19272@digraph.polyomino.org.uk>]
* Re: [PATCH] Builtin function roundeven folding implementation [not found] ` <alpine.DEB.2.21.1908232023080.19272@digraph.polyomino.org.uk> @ 2019-08-25 8:25 ` Tejas Joshi 2019-08-25 9:38 ` Martin Jambor 0 siblings, 1 reply; 6+ messages in thread From: Tejas Joshi @ 2019-08-25 8:25 UTC (permalink / raw) To: gcc; +Cc: Martin Jambor, hubicka, joseph I have made the respective changes and fixed the indentations and it passes the testing. > I encourage a followup looking for and fixing further places in the source > tree that handle round-to-integer function families (ceil / floor / trunc > / round / rint / nearbyint) and should handle roundeven as well, as that > would lead to more optimization of roundeven calls. Such places aren't > that easy to search for because most of those names are common words used > in other contexts in the compiler. But, for example, match.pd has > patterns I will follow up to make these optimizations for sure. Thanks, Tejas On Sat, 24 Aug 2019 at 02:08, Joseph Myers <joseph@codesourcery.com> wrote: > > On Fri, 23 Aug 2019, Tejas Joshi wrote: > > > diff --git a/gcc/builtins.c b/gcc/builtins.c > > index 9a766e4ad63..5149d901a96 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) > > This should use CASE_MATHFN_FLOATN, as for the other round-to-integer > functions. > > > + /* 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; > > Fix the indentation here (the braces should be indented two columns from > the "else", the contents then two columns from the braces). > > > + } > > + > > + else > > And remove the stray blank line before "else". > > > +/* 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; > > Explicitly check for rvc_zero and return false in that case (that seems to > be the convention in real.c, rather than relying on code using REAL_EXP to > do something sensible for zero, which has REAL_EXP of 0). > > > + else if (REAL_EXP (r) < SIGNIFICAND_BITS) > > + { > > Another place to fix indentation. > > > +void > > +real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt, > > + const REAL_VALUE_TYPE *x) > > +{ > > + if (is_halfway_below (x)) > > + { > > Again, fix indentation throughout this function. > > The patch is OK with those fixes, assuming the fixed patch passes testing. > I encourage a followup looking for and fixing further places in the source > tree that handle round-to-integer function families (ceil / floor / trunc > / round / rint / nearbyint) and should handle roundeven as well, as that > would lead to more optimization of roundeven calls. Such places aren't > that easy to search for because most of those names are common words used > in other contexts in the compiler. But, for example, match.pd has > patterns > > /* trunc(trunc(x)) -> trunc(x), etc. */ > > /* f(x) -> x if x is integer valued and f does nothing for such values. */ > > /* truncl(extend(x)) -> extend(trunc(x)), etc., if x is a double. */ > > /* truncl(extend(x)) and trunc(extend(x)) -> extend(truncf(x)), etc., > if x is a float. */ > > which should apply to roundeven as well. > > -- > Joseph S. Myers > joseph@codesourcery.com ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Builtin function roundeven folding implementation 2019-08-25 8:25 ` Tejas Joshi @ 2019-08-25 9:38 ` Martin Jambor 0 siblings, 0 replies; 6+ messages in thread From: Martin Jambor @ 2019-08-25 9:38 UTC (permalink / raw) To: Tejas Joshi, gcc; +Cc: hubicka, joseph Hi, On Sun, Aug 25 2019, Tejas Joshi wrote: > I have made the respective changes and fixed the indentations and it > passes the testing. Great, please send the patch (to me and to the mailing list too), so that I can commit it. Thanks, Martin ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-08-25 9:38 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <CACMrGjCu54zN+Smc7+3JF8MBZV76HXwaP-vk1HFTQGhRc=Toww@mail.gmail.com> [not found] ` <alpine.DEB.2.21.1908092021090.31221@digraph.polyomino.org.uk> [not found] ` <CACMrGjCPNr+Hjz--CL6ocV5y3GqGp13fpQCXtXJT4qeGQWk86A@mail.gmail.com> [not found] ` <ri636hug2zr.fsf@suse.cz> [not found] ` <alpine.DEB.2.21.1908211156360.6172@digraph.polyomino.org.uk> [not found] ` <ri6pnkye7ll.fsf@suse.cz> [not found] ` <alpine.DEB.2.21.1908211906340.25161@digraph.polyomino.org.uk> [not found] ` <ri6ftlte12y.fsf@suse.cz> [not found] ` <alpine.DEB.2.21.1908221426570.27000@digraph.polyomino.org.uk> 2019-08-22 16:28 ` [PATCH] Builtin function roundeven folding implementation Tejas Joshi 2019-08-22 16:35 ` Joseph Myers 2019-08-22 16:56 ` Tejas Joshi 2019-08-22 17:00 ` Joseph Myers [not found] ` <CACMrGjA3UyUYcShruM-tiT=rqBiSLX9cmSVmpX0G6SfOq_r4EQ@mail.gmail.com> [not found] ` <alpine.DEB.2.21.1908232023080.19272@digraph.polyomino.org.uk> 2019-08-25 8:25 ` Tejas Joshi 2019-08-25 9:38 ` Martin Jambor
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).