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Re: [PATCH v3 12/12] target/ppc: Use gvec to decode XVTSTDC[DS]P


From: Richard Henderson
Subject: Re: [PATCH v3 12/12] target/ppc: Use gvec to decode XVTSTDC[DS]P
Date: Thu, 20 Oct 2022 10:25:24 +1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2

On 10/19/22 22:50, Lucas Mateus Castro(alqotel) wrote:
From: "Lucas Mateus Castro (alqotel)"<lucas.araujo@eldorado.org.br>

Used gvec to translate XVTSTDCSP and XVTSTDCDP.

xvtstdcsp:
rept    loop    imm     master version  prev version        current version
25      4000    0       0,206200        0,040730 (-80.2%)    0,040740 (-80.2%)
25      4000    1       0,205120        0,053650 (-73.8%)    0,053510 (-73.9%)
25      4000    3       0,206160        0,058630 (-71.6%)    0,058570 (-71.6%)
25      4000    51      0,217110        0,191490 (-11.8%)    0,192320 (-11.4%)
25      4000    127     0,206160        0,191490 (-7.1%)     0,192640 (-6.6%)
8000    12      0       1,234719        0,418833 (-66.1%)    0,386365 (-68.7%)
8000    12      1       1,232417        1,435979 (+16.5%)    1,462792 (+18.7%)
8000    12      3       1,232760        1,766073 (+43.3%)    1,743990 (+41.5%)
8000    12      51      1,239281        1,319562 (+6.5%)     1,423479 (+14.9%)
8000    12      127     1,231708        1,315760 (+6.8%)     1,426667 (+15.8%)

xvtstdcdp:
rept    loop    imm     master version  prev version    current version
25      4000    0       0,159930        0,040830 (-74.5%)    0,040610 (-74.6%)
25      4000    1       0,160640        0,053670 (-66.6%)    0,053480 (-66.7%)
25      4000    3       0,160020        0,063030 (-60.6%)    0,062960 (-60.7%)
25      4000    51      0,160410        0,128620 (-19.8%)    0,127470 (-20.5%)
25      4000    127     0,160330        0,127670 (-20.4%)    0,128690 (-19.7%)
8000    12      0       1,190365        0,422146 (-64.5%)    0,388417 (-67.4%)
8000    12      1       1,191292        1,445312 (+21.3%)    1,428698 (+19.9%)
8000    12      3       1,188687        1,980656 (+66.6%)    1,975354 (+66.2%)
8000    12      51      1,191250        1,264500 (+6.1%)     1,355083 (+13.8%)
8000    12      127     1,197313        1,266729 (+5.8%)     1,349156 (+12.7%)

Overall, these instructions are the hardest ones to measure performance
as the gvec implementation is affected by the immediate. Above there are
5 different scenarios when it comes to immediate and 2 when it comes to
rept/loop combination. The immediates scenarios are: all bits are 0
therefore the target register should just be changed to 0, with 1 bit
set, with 2 bits set in a combination the new implementation can deal
with using gvec, 4 bits set and the new implementation can't deal with
it using gvec and all bits set. The rept/loop scenarios are high loop
and low rept (so it should spend more time executing it than translating
it) and high rept low loop (so it should spend more time translating it
than executing this code).
These comparisons are between the upstream version, a previous similar
implementation and a one with a cleaner code(this one).
For a comparison with o previous different implementation:
<20221010191356.83659-13-lucas.araujo@eldorado.org.br>

Signed-off-by: Lucas Mateus Castro (alqotel)<lucas.araujo@eldorado.org.br>
---
  target/ppc/translate/vsx-impl.c.inc | 164 ++++++++++++++++++++++++++--
  1 file changed, 154 insertions(+), 10 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~



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