The following adds X86_TUNE_AVX512_TWO_EPILOGUES tuning and directs the vectorizer to produce both a vector AVX2 and SSE epilogue for AVX512 vectorized loops when set. The tuning is enabled by default for Zen4 and Zen5 where I benchmarked it to be overall positive on SPEC CPU 2017 both in performance and overall code size. In particular it speeds up 525.x264_r which with only an AVX2 epilogue ends up in unvectorized code at the moment.
Re-bootstrap and regtest running on x86_64-unknown-linux-gnu (I've added znver4 to the defaults after benchmarking there and have to double-check no -mtune=znver4 testcase is affected). Note that znver4|znver5 is all AMD CPUs with AVX512. I did not do any benchmarking on Intel CPUs with AVX512 but I do expect 525.x264_r to improve there as well. OK for trunk if testing succeeds? Thanks, Richard. * config/i386/i386.cc (ix86_vector_costs::finish_cost): Set m_suggested_epilogue_mode according to X86_TUNE_AVX512_TWO_EPILOGUES. * config/i386/x86-tune.def (X86_TUNE_AVX512_TWO_EPILOGUES): Add. Enable for znver4 and znver5. --- gcc/config/i386/i386.cc | 12 ++++++++++++ gcc/config/i386/x86-tune.def | 5 +++++ 2 files changed, 17 insertions(+) diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index 6ac3a5d55f2..526c9df7618 100644 --- a/gcc/config/i386/i386.cc +++ b/gcc/config/i386/i386.cc @@ -25353,6 +25353,18 @@ ix86_vector_costs::finish_cost (const vector_costs *scalar_costs) && TARGET_AVX256_AVOID_VEC_PERM) m_costs[i] = INT_MAX; + /* When X86_TUNE_AVX512_TWO_EPILOGUES is enabled arrange for both + a AVX2 and a SSE epilogue for AVX512 vectorized loops. */ + if (loop_vinfo + && ix86_tune_features[X86_TUNE_AVX512_TWO_EPILOGUES]) + { + if (GET_MODE_SIZE (loop_vinfo->vector_mode) == 64) + m_suggested_epilogue_mode = V32QImode; + else if (LOOP_VINFO_EPILOGUE_P (loop_vinfo) + && GET_MODE_SIZE (loop_vinfo->vector_mode) == 32) + m_suggested_epilogue_mode = V16QImode; + } + vector_costs::finish_cost (scalar_costs); } diff --git a/gcc/config/i386/x86-tune.def b/gcc/config/i386/x86-tune.def index 6ebb2fd3414..6bbfc3c3b90 100644 --- a/gcc/config/i386/x86-tune.def +++ b/gcc/config/i386/x86-tune.def @@ -597,6 +597,11 @@ DEF_TUNE (X86_TUNE_AVX512_MOVE_BY_PIECES, "avx512_move_by_pieces", DEF_TUNE (X86_TUNE_AVX512_STORE_BY_PIECES, "avx512_store_by_pieces", m_SAPPHIRERAPIDS | m_ZNVER4 | m_ZNVER5) +/* X86_TUNE_AVX512_TWO_EPILOGUES: Use two vector epilogues for 512-bit + vectorized loops. */ +DEF_TUNE (X86_TUNE_AVX512_TWO_EPILOGUES, "avx512_two_epilogues", + m_ZNVER5) + /*****************************************************************************/ /*****************************************************************************/ /* Historical relics: tuning flags that helps a specific old CPU designs */ -- 2.43.0