On Mon, 21 Jan 2019, H.J. Lu wrote:
> TI->SF and TI->DF conversions in libgcc2.c:
>
> FSTYPE
> FUNC (DWtype u)
> {
> ...
> }
>
> have no rounding mode support. We should replace __floattisf, __floattidf,
> __floatuntisf and __floatuntidf in libgcc2.c with these from soft-fp.
Please explain what you mean by "have no rounding mode support" (i.e., the
exact flow through a function that is incorrect in a non-default rounding
mode). This patch is missing testcases - which of course should be
architecture-independent. (Any bug in libgcc2.c should first have an
architecture-independent fix - it can't be considered fixed based on a fix
for one architecture. Then, if some other approach is optimal on
particular architectures, they can get optimized variants.)
I believe all those function implementations are designed so that only a
single rounding occurs, which is for the final result, so no explicit
handling of rounding modes is ever needed (the integer code before then
may set up sticky bits appropriately to ensure the floating-point parts of
the code only need a single rounding, which works in all modes), but maybe
there are bugs in certain cases. To identify the correct fix, we need
details of the exact code path being used (the exact values of the various
macros, choices for the various conditional parts of the function, values
each variable has at each point) and where the existing,
rounding-mode-independent logic goes wrong.
--
Joseph S. Myers
jos...@codesourcery.com
