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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