[Haskell-cafe] Call pattern specialization limit messages

David Feuer david.feuer at gmail.com
Sat Jun 11 03:32:52 UTC 2016

When I compile Data.Sequence with -dppr-debug, I get several messages about
constructor specialization exceeding the call pattern limit. Things like

    Function ‘$j_ssfy{v} [lid]’
      has four call patterns, but the limit is 3
    Use -fspec-constr-count=n to set the bound
    Specialisations: [([sc_sAZr{v} [lid]],
                       [sc_sAZr{v} [lid], lvl_sdmH{v} [lid]]),
                      ([sc_sAZs{v} [lid]], [sc_sAZs{v} [lid], lvl_sw9X{v}
                      ([sc_sAZt{v} [lid]], [sc_sAZt{v} [lid], lvl_swa0{v}
                      ([sc_sAZu{v} [lid]], [sc_sAZu{v} [lid], lvl_swat{v}

How can I figure out what function this sort of thing is actually talking
about? I'd love to see what benchmarks say about whether tweaking
-fspec-constr-count is a good idea, but I don't know what to benchmark.

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