> On 9/19/23 02:44, Jin Ma wrote:
> > gcc/ChangeLog:
> >
> > * config/riscv/iterators.md (HFBF): New.
> > * config/riscv/riscv-builtins.cc (riscv_init_builtin_types):
> > Initialize data type_Bfloat16.
> > * config/riscv/riscv-modes.def (FLOAT_MODE): New.
> > (ADJUST_FLOAT_FORMAT): New.
> > * config/riscv/riscv.cc (riscv_mangle_type): Support for BFmode.
> > (riscv_scalar_mode_supported_p): Ditto.
> > (riscv_libgcc_floating_mode_supported_p): Ditto.
> > (riscv_block_arith_comp_libfuncs_for_mode): New.
> > (riscv_init_libfuncs): Opening and closing some libfuncs for BFmode.
> > * config/riscv/riscv.md (mode" ): Add BF.
> > (truncdfbf2): New.
> > (movhf): Support for BFmode.
> > (mov<mode>): Ditto.
> > (*mov<mode>_softfloat): Ditto.
> > (fix_truncbf<GPR:mode>2): New.
> > (fixuns_truncbf<GPR:mode>2): New.
> > (float<mode>bf2): New.
> > (floatuns<mode>bf2): New.
> >
> > libgcc/ChangeLog:
> >
> > * config/riscv/sfp-machine.h (_FP_NANFRAC_B): New.
> > (_FP_NANSIGN_B): New.
> > * config/riscv/t-softfp32: Add support for BF libfuncs.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.target/riscv/bf16_arithmetic.c: New test.
> > * gcc.target/riscv/bf16_call.c: New test.
> > * gcc.target/riscv/bf16_comparisons.c: New test.
> > * gcc.target/riscv/bf16_convert-1.c: New test.
> > * gcc.target/riscv/bf16_convert-2.c: New test.
> > * gcc.target/riscv/bf16_convert_run.c: New test.
> So this can't go in the tree until the extension has moved into a frozen
> state. Hopefully that'll happen before we close stage1 development in Nov.
Ok, this is very reasonable.
>
>
> > diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
> > index e00b8ee3579..5048628c784 100644
> > --- a/gcc/config/riscv/riscv.md
> > +++ b/gcc/config/riscv/riscv.md
> > @@ -1631,6 +1631,20 @@ (define_insn "truncdfhf2"
> > [(set_attr "type" "fcvt")
> > (set_attr "mode" "HF")])
> >
> > +;; The conversion of DF to BF needs to be done with SF if there is a
> > +;; chance to generate at least one instruction, otherwise just using
> > +;; libfunc __truncdfbf2.
> > +(define_expand "truncdfbf2"
> > + [(set (match_operand:BF 0 "register_operand" "=f")
> > + (float_truncate:BF
> > + (match_operand:DF 1 "register_operand" " f")))]
> > + "TARGET_DOUBLE_FLOAT || TARGET_ZDINX"
> > + {
> > + convert_move (operands[0],
> > + convert_modes (SFmode, DFmode, operands[1], 0), 0);
> > + DONE;
> > + })
> So for conversions to/from BFmode, doesn't generic code take care of
> this for us? Search for convert_mode_scalar in expr.cc. That code will
> utilize SFmode as an intermediate step just like your expander. Is
> there some reason that generic code is insufficient?
>
> Similarly for the the other conversions.
As far as I can see, the function 'convert_mode_scalar' doesn't seem to be
perfect for
dealing with the conversions to/from BFmode. It can only handle BF to HF, SF,
DF and
SF to BF well, but the rest of the conversion without any processing, directly
using
the libcall.
Maybe I should choose to enhance its functionality? This seems to be a
good choice, I'm not sure.
Jin
>
> Otherwise it looks pretty good.
>
> Jeff
