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Removed the limit on the number of traces in dumpVCD #3083

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Merged
DigitalBrains1 merged 6 commits into from
Dec 15, 2025
Merged

Removed the limit on the number of traces in dumpVCD #3083

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4009d73
Removed the limit on the number of traces in dumpVCD
The-Redstar Nov 17, 2025
8c6d1f8
Updated copyright
The-Redstar Nov 18, 2025
2a98eef
Added Peter's suggested changes
The-Redstar Nov 20, 2025
b2bda38
Removed unnecessary newlines in the VCD
The-Redstar Dec 15, 2025
a60f3a7
And added that to the changelog entry.
The-Redstar Dec 15, 2025
180e148
Minor tweaks to documentation
The-Redstar Dec 15, 2025
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1 change: 1 addition & 0 deletions changelog/2025-11-17T21_35_22+01_00_fixed_dumpvcd_trace_limit
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
FIXED: Removed the limit on the number of traces in `dumpVCD`. Also removed unnecessary double newlines after 1-bit signals. [#3082](https://github.com/clash-lang/clash-compiler/issues/3082)
22 changes: 12 additions & 10 deletions clash-prelude/src/Clash/Signal/Trace.hs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
{-|
Copyright : (C) 2018, Google Inc.
2019, Myrtle Software Ltd
2022-2024, QBayLogic B.V.
2022-2025, QBayLogic B.V.
License : BSD2 (see the file LICENSE)
Maintainer : QBayLogic B.V. <devops@qbaylogic.com>

Expand Down Expand Up @@ -115,6 +115,7 @@ import Data.IORef
import Data.List (foldl')
#endif
import Data.List (foldl1', unzip4, transpose, uncons)
import Data.List.Extra (snoc)
import qualified Data.Map.Strict as Map
import Data.Maybe (fromMaybe, catMaybes)
import qualified Data.Text as Text
Expand Down Expand Up @@ -349,8 +350,6 @@ dumpVCD## (offset, cycles) traceMap now
error $ "dumpVCD: cycles was " ++ show cycles ++ ", but cannot be negative."
| null traceMap =
error $ "dumpVCD: no traces found. Extend the given trace names."
| Map.size traceMap > 126 - 33 =
Left $ "Tracemap contains more than 93 traces, which is not supported by VCD."
| (nm:_) <- offensiveNames =
Left $ unwords [ "Trace '" ++ nm ++ "' contains"
, "non-printable ASCII characters, which is not"
Expand All @@ -373,7 +372,10 @@ dumpVCD## (offset, cycles) traceMap now
where
offensiveNames = filter (any (not . printable)) traceNames

labels = map chr [33..126]
-- Generate labels in the pattern a,b,c,aa,ab,ac,ba,bb,bc,ca,cb,cc,aaa,...
labels = concatMap (\s -> map (snoc s) alphabet) ([]: labels)
where
alphabet = map chr [33..126]

timescale = foldl1' gcd (Map.keys periodMap)
periodMap = toPeriodMap traceMap
Expand Down Expand Up @@ -413,22 +415,22 @@ dumpVCD## (offset, cycles) traceMap now
headerTimescale = ["$timescale", (show timescale) ++ "ps", "$end"]
headerWires = [ Text.unwords $ headerWire w l n
| (w, l, n) <- (zip3 widths labels traceNames)]
headerWire w l n = map Text.pack ["$var wire", show w, [l], n, "$end"]
headerWire w l n = map Text.pack ["$var wire", show w, l, n, "$end"]
initValues = map Text.pack $ zipWith ($) formatters inits

formatters = zipWith format widths labels
inits = map (maybe (error "dumpVCD##: empty value") fst . uncons) valuess'
tails = map changed valuess'

-- | Format single value according to VCD spec
format :: Width -> Char -> Value -> String
format 1 label (0,0) = ['0', label, '\n']
format 1 label (0,1) = ['1', label, '\n']
format 1 label (1,_) = ['x', label, '\n']
format :: Width -> String -> Value -> String
format 1 label (0,0) = '0': label
format 1 label (0,1) = '1': label
format 1 label (1,_) = 'x': label
format 1 label (mask,val) =
error $ "Can't format 1 bit wide value for " ++ show label ++ ": value " ++ show val ++ " and mask " ++ show mask
format n label (mask,val) =
"b" ++ map digit (reverse [0..n-1]) ++ " " ++ [label]
"b" ++ map digit (reverse [0..n-1]) ++ " " ++ label
where
digit d = case (testBit mask d, testBit val d) of
(False,False) -> '0'
Expand Down