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18 Commits

Author SHA1 Message Date
Jannis Harder 7b74caa5db peepopt: Fix padding for the peepopt_shiftmul_right pattern 
The previous version could easily generate a large amount of padding
when the constant factor was significantly larger than the width of the
shift data input. This could lead to huge amounts of logic being
generated before then being optimized away at a huge performance and
memory cost.

Additionally and more critically, when the input width was not a
multiple of the constant factor, the input data was padded with 'x bits
to such a multiple before interspersing the 'x padding needed to align
the selectable windows to power-of-two offsets.

Such a final padding would not be correct for shifts besides $shiftx,
and the previous version did attempt to remove that final padding at the
end so that the native zero/sign/x-extension behavior of the shift cell
would be used, but since the last selectable window also got
power-of-two padding appended after the padding the code is trying to
remove got added, it did not actually fully remove it in some cases.

I changed the code to only add 'x padding between selectable windows,
leaving the last selectable window unpadded. This omits the need to add
final padding to a multiple of the constant factor in the first place.
In turn, that means the only 'x bits added are actually impossible to
select. As a side effect no padding is added when the constant factor is
equal to or larger than the width of the shift data input, also solving
the reported performance bug.

This fixes #4056
 2023-12-06 18:35:44 +01:00
Marcelina Kościelnicka a0e99a9f3f peepopt: Remove now-redundant dffmux pattern. 2020-08-07 13:21:34 +02:00
Eddie Hung 045f344038 Use `sat -tempinduct` and comments for why equiv_opt not sufficient 2019-10-03 11:11:50 -07:00
Eddie Hung e9645c7fa7 Fix broken CI, check reset even for constants, trim rstmux 2019-10-02 21:26:26 -07:00
Eddie Hung e4bd5aaebf Fix test 2019-10-02 18:12:25 -07:00
Eddie Hung f6fabc8fda Update test 2019-10-02 18:03:45 -07:00
Eddie Hung e730a595ee Add test 2019-10-02 18:01:41 -07:00
Eddie Hung f492567c87 Oops 2019-09-13 18:19:07 -07:00
Eddie Hung a2eee9ebef Add counter-example from @cliffordwolf 2019-09-13 16:41:10 -07:00
Eddie Hung 14d72c39c3 Revert "Make one check $shift(x)? only; change testcase to be 8b" 
This reverts commit e2c2d784c8.
 2019-09-13 16:33:18 -07:00
Eddie Hung bdb5e0f29c Cope with presence of reset muxes too 2019-09-11 13:36:37 -07:00
Eddie Hung f46ef47893 Add more tests 2019-09-11 13:22:41 -07:00
Eddie Hung 3a8582081e proc instead of prep 2019-09-11 00:14:06 -07:00
Eddie Hung 580faae8ad Add unsigned case 2019-09-11 00:07:17 -07:00
Eddie Hung 97e1520b13 Missing equiv_opt -assert 2019-09-06 22:50:03 -07:00
Eddie Hung e2c2d784c8 Make one check $shift(x)? only; change testcase to be 8b 2019-09-06 22:48:23 -07:00
Eddie Hung 51b559af2c Usee equiv_opt -assert 2019-09-06 22:48:04 -07:00
Eddie Hung ef0681ea4c simple/peepopt.v tests to various/peepopt.ys with equiv_opt & select 2019-09-05 08:43:22 -07:00