Tighten inferred width for PopCount #1033
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ucbjrl
approved these changes
Mar 15, 2019
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An artifact of SeqUtils.count's implementation strategy makes its result one bit too wide, except for the case that the number of inputs is exactly a power of two.
count(Seq(b, c))expands tob +& c, which is 2 bits wide, as you'd hope.count(Seq(a, b, c))expands tocount(Seq(a)) +& count(Seq(b, c)), which is 3 bits wide, even though only 2 bits are needed to represent the result.A simple fix is to truncate the sum at every step.
Type of change: other enhancement
Impact: API modification
Development Phase: implementation
Release Notes
Reduce width of PopCount output to minimal possible value.