Happy New Year, everybody! A colleague just had a question for me about DW_OP_implicit_value which led me to wonder why we have both that and DW_OP_stack_value. Looking at http://dwarfstd.org/ShowIssue.php?issue=071227.1 which introduced the latter, it says in part:
(This operator is similar to DW_OP_implicit_value, issue "070426.1". The latter only permits the description of values known to be literals at compile-time; this proposal permits the description of values which have known expressions at compile-time. It is more general; since a sequence of DW_OP_constxx, DW_OP_value can replace every instance of DW_OP_implicit_value, this proposal also includes the removal of DW_OP_implicit value from the standard.) ...although I don't think "the removal of DW_OP_implicit_value" actually happened. I have come up with only two advantages that DW_OP_implicit_value would have, compared to DW_OP_stack_value: 1) it can express a value larger than one expression-stack element in a single operation; 2) it's faintly possible that it's simpler for a producer to produce. But, DW_OP_stack_value would frequently result in a more compact representation, for example: DW_OP_implicit_value 4 0 0 0 0 => 6 bytes DW_OP_lit0 DW_stack_value => 2 bytes I don't see much value 😉 in actually deprecating or removing DW_OP_implicit_value, now that it's out in the world; is it worth adding a non-normative note that DW_OP_stack_value is actually more general? Thanks, --paulr _______________________________________________ Dwarf-Discuss mailing list Dwarf-Discuss@lists.dwarfstd.org http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org
