Optimize Compilation of nested Lambdas

[jogibear9988]

Net Frameworks compile of Lambda's sometimes inserts nested Lambdas directly to the Parent Lambda! See Test: Issue83_linq2db.TestLambdaInvokeSupported2 and view IL of both compiled methods

[dadhi]

Interesing, the only case for this I eould imagine in creating lambda and immediately invoking.

[jogibear9988]

why? also when it‘s only invoked once it makes sence! why should we then do the overhead?

[jogibear9988]

When I looked at the IL, the Lambda is always included!

[dadhi]

Of course, if we can detect such cases we may inline the lambda body.

[dadhi]

We may also consider other expression reductions, like the Block with the single expression, may be others.

[jogibear9988]

as there is no code for a block emited, what would you optimize if there is only one expression contained?
could you count in the first parse round, how often a lambda is used?

[dadhi]

Regarding the emitted code for block there is no gains, but regarding infrastructure, e.g. BlockInfo, stack depth, etc. it maybe useful.

Lambda usage, maybe. Need to think it out.

[dadhi]

More thoughts..

It happens that we may safely replace the labda invocation with the lambda body if has no arguments.

For lambda with args, there is need to be a substitution process, which is unclear to me.

So we win only in rare cases, adding complexity to the code (and affecting hot path). The case also may be solved on consumer side, by simplifying such invocations in the first place!

Does not worth it in my oppinion.

[jogibear9988]

in linq2db it‘s used. and microsoft code does it.
but I think it‘s not critical. and i also dont know why we use two lambdas at linq2db.

maybe I look to fix it, when I‘ve time.

[dadhi]

@jogibear9988 fixed, check my commit for details

[jogibear9988]

Do you now inline it always? Independed of the invocation count?

[dadhi]

Yep. if you have a big-big lambda, without arguments, you may always precompile it separately.

I doubt that it will create more cons vs pros.