On Fri, 26 May 2017, Richard Biener wrote:
On Fri, May 26, 2017 at 11:52 AM, Marc Glisse <marc.gli...@inria.fr> wrote:
Hello,
coming back to https://gcc.gnu.org/ml/gcc-patches/2014-02/msg01378.html ,
Richard wanted a complete set of fenv functions instead of just the 2 I was
interested in. However, most functions in fenv.h handle a struch fenv_t or
fexcept_t, which makes them inconvenient to handle as builtins.
We do have stdio functions having FILE * arguments. There's 'fileptr_type_node'
(pointer to incomplete struct) to handle that. I suppose rth was looking for
sth similar for fenv_t * and fexcept_t *. I guess it's hard to implement a
dependency scheme other than "memory" without seeing the full set of
functions.
I'll see how hard it is to imitate FILE*...
Similarly, I
don't see div as a builtin in that file, only FILE* has special code, but
that doesn't seem worth the trouble here. So I am only declaring the 5
"simple" functions, with minimal properties: leaf, nothrow, and for
fegetround pure (glibc already declares it that way). We can then discuss
the safety of future optimizations on a case by case basis.
+DEF_C99_BUILTIN (BUILT_IN_FERAISEEXCEPT, "feraiseexcept",
BT_FN_INT_INT, ATTR_NOTHROW_LEAF_LIST)
I think feraiseexcept shouldn't be nothrow?
glibc marks it as nothrow. I can remove the nothrow flag for now, for
safety. It may trap, but it does not throw a C++ exception AFAIU.
But it may be pure?
It writes to the exception register (aka memory for now), so I would
hardly call it pure.
Likewise fetestexcept may be pure?
Too unsafe for now, since any FP operation can write to the memory that
fetestexcept reads.
--
Marc Glisse
