[PATCH v3 0/5] target/s390x: Implement DIVIDE TO INTEGER

[Ilya Leoshkevich <iii@linux.ibm.com>]

v2: https://lore.kernel.org/qemu-devel/20260127153736.62730-1-iii@linux.ibm.com/
v2 -> v3: Use FloatParts64 (Richard).
          Improve "smallish" comment (Richard).
          Use parts_muladd_scalbn (Richard).
          Get rid of manual precision rounding (Richard).
          New patch: parts_round_to_int_normal() improvement.
          New 64-bit testcase for a fuzzer finding on one of the
          intermediate versions. I have to admit I did not put down and
          then forgot what exactly it was about, but it must be
          interesting, so I decided to keep it.

v1: https://lore.kernel.org/qemu-devel/20260121222116.713325-1-iii@linux.ibm.com/
v1 -> v2: Move the implementatation to fpu/ and rewrite using
          FloatParts (Richard). I can't say I particularly like the way
          it looks, but at least most macros are gone and it survives
          fuzzing.
          Explain why we need -O0 for the test (Alex).
          New patch: s390_get_bfp_rounding_mode().
          Add a few comments with calculation examples to the test.

Hi,

This series implements DIVIDE TO INTEGER instruction, which is
required to run LuaJIT.

Patch 1 is a debugging helper, patch 2 is a small refactoring, patch 3
is an improvement for an FPU rounding helper, patch 4 is the
implementation.

Since the instruction is quite complex, I've extensively tested it
using a libFuzzer-based harness [1] that compares emulation with native
execution at ~15k exec/s. The tests (patch 5) use data generated
this way.

Best regards,
Ilya

[1] https://github.com/iii-i/qemu/commits/iii/wip/fuzz-tcg-v1/

Ilya Leoshkevich (5):
  target/s390x: Dump Floating-Point-Control Register
  target/s390x: Extract s390_get_bfp_rounding_mode()
  fpu: Restrict parts_round_to_int_normal to target precision
  target/s390x: Implement DIVIDE TO INTEGER
  tests/tcg/s390x: Test DIVIDE TO INTEGER

 fpu/softfloat-parts.c.inc           |   7 +-
 fpu/softfloat.c                     | 144 +++++++++++++++
 include/fpu/softfloat.h             |  11 ++
 target/s390x/cpu-dump.c             |   1 +
 target/s390x/helper.h               |   1 +
 target/s390x/tcg/fpu_helper.c       | 118 +++++++++----
 target/s390x/tcg/insn-data.h.inc    |   5 +-
 target/s390x/tcg/translate.c        |  26 +++
 tests/tcg/s390x/Makefile.target     |   5 +
 tests/tcg/s390x/divide-to-integer.c | 265 ++++++++++++++++++++++++++++
 10 files changed, 545 insertions(+), 38 deletions(-)
 create mode 100644 tests/tcg/s390x/divide-to-integer.c

-- 
2.52.0