On Tue, May 6, 2025 at 10:54 AM Liu, Hongtao <hongtao....@intel.com> wrote: > > > > > -----Original Message----- > > From: H.J. Lu <hjl.to...@gmail.com> > > Sent: Thursday, May 1, 2025 6:39 AM > > To: GCC Patches <gcc-patches@gcc.gnu.org>; Uros Bizjak > > <ubiz...@gmail.com>; Liu, Hongtao <hongtao....@intel.com> > > Subject: [PATCH] x86: Skip if the mode size is smaller than its natural size > > > > When generating a SUBREG from V16QI to V2HF, validate_subreg fails since > > the V2HF size (4 bytes) is smaller than its natural size (word size). > > Update remove_redundant_vector_load to skip if the mode size is smaller > > than its natural size. > I think we can also handle it in replace_vector_const by inserting an extra > move with > (Set (reg:v4qi) (subreg:v4qi (v16qi const0_rtx) 0)) > And then use subreg with same vector size (v2hf<->v4qi) > (set (reg:v2hf) (subreg:v2hf (reg:v4qi) 0))
What is the advantage of this approach? My patch uses a single instruction to write 4 bytes of 0s and 1s. Your suggestion needs at least one more instruction. > I think this can also pass validate_subreg. > > > > gcc/ > > > > PR target/120036 > > * config/i386/i386-features.cc (remove_redundant_vector_load): > > Also skip if the mode size is smaller than its natural size. > > > > gcc/testsuite/ > > > > PR target/120036 > > * g++.target/i386/pr120036.C: New test. > > > > -- > > H.J. -- H.J.
