https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106117
Bug ID: 106117
Summary: Use of option -fexcess-precision for
operation-by-operation emulation for _Float16
arithmetics.
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: Zahira.Ammarguellat at intel dot com
Target Milestone: ---
We are adding in Clang the support of '_Float16' on X86 targets with SSE2
enabled.
When the target supports AVX512-FP16, Clang performs '_Float16' arithmetic
using native support. Otherwise, '_Float16' arithmetic is performed by
promoting to 'float', then performing the operation, and finally truncating to
'_Float16'.
This operation-by-operation emulation is the default in Clang, and is in line
with the C standard's rules for excess precision arithmetic. We would like to
adopt the option '-fexcess-precision' to request this operation-by-operation
emulation by setting '-fexcess-precision=none'.
First are there any objections in using this option to request
operation-by-operation emulation for '_Float16' arithmetic?
Second is 'none' the right value to use?
Thanks.
