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Re: About GSOC.
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Tejas Joshi <tejasjoshi9673 at gmail dot com>
- Cc: <gcc at gcc dot gnu dot org>
- Date: Mon, 21 Jan 2019 23:02:59 +0000
- Subject: Re: About GSOC.
- References: <CACMrGjCeaZ7EoYqjLYiAJXjOtOfpJNo9zcbWhfarfkiLMN8YYA@mail.gmail.com> <CACMrGjCJ3r9+iNnFUOdajH+73HYHexv+mn7p_MHtn4jUn0d7-Q@mail.gmail.com> <ri6k1m9q6rm.fsf@suse.cz> <alpine.DEB.2.21.1810231631010.17157@digraph.polyomino.org.uk> <CACMrGjB6WLp0YS17b3prvbxvYnKtEsxhN3NOePN5SPVazNRM3A@mail.gmail.com> <alpine.DEB.2.21.1811161645480.12454@digraph.polyomino.org.uk> <CACMrGjC64UmP5-_hSiXyXrb2+cyqDqZ9iQMYJNn+mOKZ6G_LeQ@mail.gmail.com>
On Tue, 22 Jan 2019, Tejas Joshi wrote:
> the number like nan or normal in the functions. Though, attributes of
> struct real_value are pretty unclear to me regarding to the number it
> represents. (Am I right within this grasp?).
It may be helpful to run the compiler under a debugger to examine how
particular real numbers are represented in real_value - that should help
answer questions such as what endianness is used for the significand, or
whether floating point values with a given exponent are in the range
[2^EXP, 2^(EXP+1)) or [2^(EXP-1), 2^EXP), where conventions commonly
differ. (It's the unoptimized, stage1 cc1 that should be run under a
debugger. See <https://gcc.gnu.org/wiki/DebuggingGCC> for more details.)
And of course contribute comments in real.h once you've determined the
answers - because there are such areas where conventions about
representation of floating-point numbers commonly differ, it's
particularly valuable to have such comments because even someone familiar
with floating-point won't know which convention has been chosen by this
code in GCC.
--
Joseph S. Myers
joseph@codesourcery.com