> to how ($var || 2) could be false. Can it

Nope, but a method of a tied variable could raise an exception or goto label.

A tied variable could also have side effects, like logging each access.

IOW the FETCH can't be short circuited, even if the result is of no interest.

Anyway optimizer rules are very simplistic, and if wanted such exotic edge cases could be forbidden in documentation.

Tied variables are hell for any optimizer, I remember a talk of Reini Urban in Kiev where he presented details of his optimizer with factor 2 speed gain. I was so puzzled how one technique works and asked how this can handle tied variables.

His answer was simple: tied variables are not allowed! :)

Anyway JS shows that JIT compiling is the way to go.

(NB no tied vars in ECMA JS)

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)

PS: Je suis Charlie!

update

There are several cases where optimization already causes strange effects.

For instance try to goto into a code chunk which is optimized away with 'if(0)'

In reply to Re^3: Compiler Optimization by LanX
in thread Compiler Optimization by three18ti

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