[Libre-soc-bugs] [Bug 784] Implement cl* instructions for carry-less operations

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=784

--- Comment #41 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #40)
> 
> ah, missed that.
> 
> apparently yosys isn't optimizing the adder chain to just 1 add per clock
> cycle

fixed that:
commit 4ee201e6cae8475621647f7b3b9839292ed0b46f (HEAD -> master, origin/master)
Author: Jacob Lifshay <programmerjake at gmail.com>
Date:   Thu May 5 20:10:32 2022 -0700

    split step counter into clock and substep

    this allows substep to be completely optimized away by yosys for
CLDivRemFSMStage

I ran the comparison by running:
python src/nmigen_gf/hdl/test/test_cldivrem.py -k test_64_step_8
yosys <<'EOF'                                                   
read_rtlil sim_test_out/__main__.TestCLDivRemFSM.test_64_step_8/0.il
flatten
synth
;;;
stat
ltp -noff
EOF

old unsplit step algorithm:
https://git.libre-soc.org/?p=nmigen-gf.git;a=commit;h=e59b7ccf6c066fc0ecac6410e9b6447d5af77533

   Number of cells:               5046
     $_ANDNOT_                     302
     $_AND_                         67
     $_MUX_                       3283
     $_NAND_                        12
     $_NOR_                         77
     $_NOT_                        323
     $_ORNOT_                       61
     $_OR_                          58
     $_SDFFE_PP0P_                  72
     $_SDFF_PP0_                   197
     $_SDFF_PP1_                     1
     $_XNOR_                       149
     $_XOR_                        444

Longest topological path in top (length=36):

New algorithm where step is split into clock and substep:
https://git.libre-soc.org/?p=nmigen-gf.git;a=commit;h=4ee201e6cae8475621647f7b3b9839292ed0b46f

   Number of cells:               4818
     $_ANDNOT_                     290
     $_AND_                         45
     $_MUX_                       3297
     $_NAND_                         6
     $_NOR_                         68
     $_NOT_                        196
     $_ORNOT_                       41
     $_OR_                          62
     $_SDFFE_PP0N_                   6
     $_SDFFE_PP0P_                  70
     $_SDFF_PP0_                   190
     $_SDFF_PP1_                     1
     $_XNOR_                       136
     $_XOR_                        410

Longest topological path in top (length=31):

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