Dear Jakub, Thank you for your reply promptly. I have tried many test cases, but I still cannot trigger the functions: decode_ieee_xxx(). Can you give me some cases for studying?
Thank you. Peng-Sheng On Mon, Sep 19, 2022 at 9:36 PM Jakub Jelinek <ja...@redhat.com> wrote: > On Mon, Sep 19, 2022 at 09:22:55PM +0800, pengsheng.chen--- via Gcc wrote: > > The functions encode_ieee_single()/encode_ieee_double() encode the GCC > > internal representation (i.e., REAL_VALUE_TYPE) to the corresponding IEEE > > single precision/double precision formats. The constant values in a > program > > (i.e., float a = 3.14;) will be parsed and then transferred to GCC > > REAL_VALUE_TYPE. Later, the REAL_VALUE_TYPE is encoded to IEEE > > single/double formats. However, I do not know why we need > > decode_ieee_single()/decode_ieee_double()? Which situations or C code > > fragments are these decode_ieee_xxx functions used in? > > Anywhere where real_from_target is called. > That is usually when you say have a union of one of the floating point > types and corresponding integral type, you store the integer into the > union and read back the floating point, so e.g. when folding > in the IL VIEW_CONVERT_EXPR <float> (some_int_value) etc. > Or e.g. when folding RTL NOT of a constant, that inverts all the bits, > so you need real_to_target, invert the bits and real_from_target back. > > Jakub > >
