Re: [PATCH] xtensa: Implement l(ceil|floor|round|)sfsi2 insn patterns and their scaled variants

[Takayuki 'January June' Suwa]

On 2025/06/05 5:09, Max Filippov wrote:

Hi Suwa-san,

Hi Max, (thanks for every regtesting)

On Tue, Jun 3, 2025 at 7:44 AM Takayuki 'January June' Suwa
<jjsuwa_sys3...@yahoo.co.jp> wrote:

By using the previously unused CEIL|FLOOR|ROUND.S floating-point coprocessor
instructions.  In addition, two instruction operand format codes are added
to output the scale value as assembler source.

      /* example */
      int test0(float a) {
        return __builtin_lceilf(a);
      }
      int test1(float a) {
        return __builtin_lfloorf(a * 2);
      }
      int test2(float a) {
        /* __builtin_lroundf() requires -fno-math-errno */
        return __builtin_lroundf(a * 32768);
      }

      ;; result
      test0:
         entry   sp, 32
         wfr     f0, a2
         ceil.s  a2, f0, 0
         retw.n
      test1:
         entry   sp, 32
         wfr     f0, a2
         floor.s a2, f0, 1
         retw.n
      test2:
         entry   sp, 32
         wfr     f0, a2
         round.s a2, f0, 15
         retw.n

gcc/ChangeLog:

         * config/xtensa/xtensa.cc (printx, print_operand):
         Add two instruction operand format codes 'U' and 'V',
         whose represent scale factors of 0 to 15th positive/negative
         power of two.
         * gcc/config/xtensa/xtensa.md (c_enum "unspec"):
         Add UNSPEC_CEIL, UNSPEC_FLOOR and UNSPEC_ROUND.
         (int_iterator ANY_ROUND, int_attr m_round):
         New integer iterator and its attribute.
         (fix<s_fix>_truncsfsi2, *fix<s_fix>_truncsfsi2_2x,
         *fix<s_fix>_truncsfsi2_scaled, float<s_float>sisf2,
         *float<s_float>sisf2_scaled):
         Use output templates with the operand formats added above,
         instead of individual output statements.
         (l<m_round>sfsi2, *l<m_round>sfsi2_2x, *l<m_round>sfsi2_scaled):
         New insn patterns.
---
   gcc/config/xtensa/xtensa.cc | 16 ++++++++++++
   gcc/config/xtensa/xtensa.md | 52 ++++++++++++++++++++++++++++---------
   2 files changed, 56 insertions(+), 12 deletions(-)

This passes without new regressions on targets without FPU, but I see
a few new failures in the gfortran testsuite on a target with FPU:

+FAIL: gfortran.dg/nint_2.f90   -O0  execution test
+FAIL: gfortran.dg/out_of_range_1.f90   -O0  execution test
+FAIL: gfortran.dg/out_of_range_1.f90   -O1  execution test
+FAIL: gfortran.dg/out_of_range_1.f90   -O2  execution test
+FAIL: gfortran.dg/out_of_range_1.f90   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
+FAIL: gfortran.dg/out_of_range_1.f90   -O3 -g  execution test
+FAIL: gfortran.dg/out_of_range_1.f90   -Os  execution test
+FAIL: gfortran.dg/out_of_range_2.f90   -O0  execution test
+FAIL: gfortran.dg/out_of_range_2.f90   -O1  execution test
+FAIL: gfortran.dg/out_of_range_2.f90   -O2  execution test
+FAIL: gfortran.dg/out_of_range_2.f90   -O3 -fomit-frame-pointer
-funroll-loops -fpeel-loops -ftracer -finline-functions  execution
test
+FAIL: gfortran.dg/out_of_range_2.f90   -O3 -g  execution test
+FAIL: gfortran.dg/out_of_range_2.f90   -Os  execution test

At first glance they may be related to the rounding mode settings,
let me take a closer look.

gccint says l(ceil/floor/round)sfsi2 are not interested in the current
rounding mode.  Similary, Xtensa ISA refman says CEIL/FLOOR/ROUND.S will
not affect the current rounding mode.

IMHO I suspect that the behavior for out-of-range input values, e.g. values
​​that do not fit in signed 32 bits, infinity or NaN, may be different.

=====
jjsuwa_sys3...@yahoo.co.jp