I mention WPO because of other procedures calling them. It would be
very impractical to go back to procedures that have already gone through
the peephole optimizer etc and change the references, especially if said
reference is converted into a raw offset (I'm not absolutely sure when
it's converted into a raw offset and when it's a reference that's
converted by the assembler).
Gareth aka. Kit
On 19/07/2021 00:37, Martin Frb via fpc-devel wrote:
On 19/07/2021 01:24, J. Gareth Moreton via fpc-devel wrote:
The final assembly language of each method is identical.
(Note that the trunk is not this efficient just yet... it still
leaves a "movq %rcx,%rax" instruction prior to "movl $1,%r8d" and
then calls "movq (%rax),%rax" instead of "movq (%rcx),%rax" - it's
still all identical though).
Would it be plausible to calculate and store a form of message digest
(hash) of the final form of the tai entries or machine code and
identify collisions and potential duplicate procedures for
whole-program optimization? Granted I don't know anything about WPO
yet so I don't know how plausible this is. This wouldn't be
somethind done on quick or debug builds because you'll need to be
able to do proper stack traces, and having identical procedures
merged into one might cause confusion.
Why WPO?
When you compute this hash, you could immediately check if it already
exists. (either in this unit, or any unit used).
The only miss would be, if 2 units, that do not see each other include
identical code. That part could then still be a WPO.
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