[VM] CompiledMethod header format?

Bob Arning arning at charm.net
Sat Dec 30 02:54:34 UTC 2000


On Fri, 29 Dec 2000 20:22:48 -0500 (EST) "Matthew S. Davis" <mdavis at cse.psu.edu> wrote:
>     I've determined the following header format from the Interpreter
>methods:
>
>bit  0       : constant 1 to indicate SmallInteger
>bits 1-9     : primitive index
>bits 10-17   : literal count
>bit  18      : not used?
>bits 19-25   : temporary count
>bits 25-28   : argument count
>bits 29-31   : primitive index
>
>     Could someone please explain why bit 25 is shared between two
>fields?  I'm not clear why this is the case.  Should the temporary count
>really be in bit positions 18-24?  If so, it does not look like they are.

Matthew,

Temporary count is definitely 6 bits in the header. Where did you see an indication that it was 7?

And the bit you have marked as unused is the Large/Small context flag.

Cheers,
Bob





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