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- From: Tejas Joshi <tejasjoshi9673 at gmail dot com>
- To: gcc at gcc dot gnu dot org
- Date: Sat, 13 Oct 2018 10:13:00 +0530
- Subject: About GSOC.
- References: <CACMrGjCeaZ7EoYqjLYiAJXjOtOfpJNo9zcbWhfarfkiLMN8YYA@mail.gmail.com>
I reached asking about GCC GSoC project about adding and
like roundeven. I could not apply for the idea this year but
interested in the peoject and
really hoping it would be carry forwarded. Since I've been studying
source code and about the project, I think working on this from now
would give me some heads up and hands on with the source code.
I did study <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1778.pdf>.
It does tell that roundeven rounds its argument to nearest integral
ties to even (least significant bit 0) returning integral value
provided that the resulting value is exact.
So, for the start, I'd be implementing this functionality for roundeven.
As ita said in earlier mails that, similar functions like
real_ceil are implemented
in real.c and are used in fold-const-call.c.
Roundeven might be implemented in similar way. Is it built-in
(internal) function means not to be exposed to end-user?
Studying some functions like real_ceil, there are call checks
(flag_errno_math) so I believe similar would be needed for roundeven.
In real.c where real_ceil is implemented, there are function calls
(and implementations) like do_fix_trunc which also then call functions
like decimal_do_dix_trunc (maybe the main functionality of
do_fix_trunc?, other are just checks, like NaN or qNaN). I did not
understand these functions really and what do they do. Also I did not
understand the structure of REAL_VALUE_TYPE (r->cl and etc?)
Also when does the real.c and fold-const-call.c comes in picture in
the flow of GCC (Is it for GIMPLE level instruction selection (gimple
stmnt to corresponding rtl instruction))?