[Issue 13061] New: [GC] investigate using compressed bitmaps for attribute bits

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13061

          Issue ID: 13061
           Summary: [GC] investigate using compressed bitmaps for
                    attribute bits
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: safety0ff.bugz at gmail.com

We're currently using a considerable amount of space storing bitmaps.
I suspect the  bit patterns within them are good candidates for compression.

The attributes which aren't aren't used during marking inner loop are good
candidates for compression as they are less performance sensitive.

There's even room for improvement with the eagerly allocated "scan" bit set
which are only used for deferred scanning of blocks when a deep heap graph is
encountered.

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