On Sun, Jul 14, 2024 at 4:05 AM Takayuki 'January June' Suwa
<jjsuwa_sys3...@yahoo.co.jp> wrote:
>
> [U]FLOAT.S machine instruction in Xtensa ISA, which converts an integer to
> a hardware single-precision FP register, has the ability to divide the
> result by power of two (0 to 15th).
>
> Similarly, [U]TRUNC.S instruction, which truncates single-precision FP to
> integer, can multiply the source value by power of two in advance, but
> neither of these currently uses this function (always specified with 0th
> power of two, i.e. a scaling factor of 1).
>
> This patch unleashes the scaling ability of the above instructions.
>
> /* example */
> float test0(int a) {
> return a / 2.f;
> }
> float test1(unsigned int a) {
> return a / 32768.f;
> }
> int test2(float a) {
> return a * 2;
> }
> unsigned int test3(float a) {
> return a * 32768;
> }
>
> ;; before
> test0:
> movi.n a9, 0x3f
> float.s f0, a2, 0
> slli a9, a9, 24
> wfr f1, a9
> mul.s f0, f0, f1
> rfr a2, f0
> ret.n
> test1:
> movi.n a9, 7
> ufloat.s f0, a2, 0
> slli a9, a9, 27
> wfr f1, a9
> mul.s f0, f0, f1
> rfr a2, f0
> ret.n
> test2:
> wfr f1, a2
> add.s f0, f1, f1
> trunc.s a2, f0, 0
> ret.n
> test3:
> movi.n a9, 0x47
> slli a9, a9, 24
> wfr f1, a2
> wfr f2, a9
> mul.s f0, f1, f2
> utrunc.s a2, f0, 0
> ret.n
>
> ;; after
> test0:
> float.s f0, a2, 1
> rfr a2, f0
> ret.n
> test1:
> ufloat.s f0, a2, 15
> rfr a2, f0
> ret.n
> test2:
> wfr f0, a2
> trunc.s a2, f0, 1
> ret.n
> test3:
> wfr f0, a2
> utrunc.s a2, f0, 15
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/predicates.md
> (fix_scaling_operand, float_scaling_operand): New predicates.
> * config/xtensa/xtensa.md
> (any_fix/m_fix/s_fix, any_float/m_float/s_float):
> New code iterators and their attributes.
> (fix<s_fix>_truncsfsi2): Change from "fix_truncsfsi2".
> (*fix<s_fix>_truncsfsi2_2x, *fix<s_fix>_truncsfsi2_scaled):
> New insn definitions.
> (float<s_float>sisf2): Change from "floatsisf2".
> (*float<s_float>sisf2_scaled): New insn definition.
> ---
> gcc/config/xtensa/predicates.md | 20 ++++++++++++
> gcc/config/xtensa/xtensa.md | 58 ++++++++++++++++++++++++++-------
> 2 files changed, 66 insertions(+), 12 deletions(-)
Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master
--
Thanks.
-- Max
