Support Full NGEN with IBC

[brianrob]

Today, the target EnablePartialNGENOptimization unconditionally specifies -partialNGEN to ibcmerge.exe (

arcade/src/Microsoft.DotNet.Arcade.Sdk/tools/OptimizationData.targets

Line 119 in 660f6cd

<IbcMergeArgs>-q -f -partialNGEN -minify -delete -mo "%(_AssemblyWithRawIbcData.OptimizeAssemblyPath)" -incremental "%(_AssemblyWithRawIbcData.PreviousAssemblyCopyPath)"</IbcMergeArgs>

) which means that any users of this target will get partial NGEN.

The bulk of IBC users should be fully pre-compiling their assemblies. One way to address this would be to add a new target that uses most of the machinery of EnablePartialNGENOptimization but doesn't specify -partialNGEN to ibcmerge.exe.

@tmat, @billwert

[tmat]

The bulk of IBC users should be fully pre-compiling their assemblies.

I wouldn't say that. Anything that is inserted into VS needs to be partial NGEN'd.

One way to address this would be to add a new target that uses most of the machinery of EnablePartialNGENOptimization but doesn't specify -partialNGEN to ibcmerge.exe.

How does full NGEN differ from partial NGEN in terms of IBC merge logic? Is it just the absence of -partialNGEN parameter or is there something else?

[brianrob]

How does full NGEN differ from partial NGEN in terms of IBC merge logic? Is it just the absence of -partialNGEN parameter or is there something else?

Yes. The partialNGEN flag sets a bit in the binary that tells NGEN to perform a partial precompilation based on IBC data. If you remove the partialNGEN flag then it does a full precompilation.

I wouldn't say that. Anything that is inserted into VS needs to be partial NGEN'd.

Understood. However, the bulk of binaries don't get inserted into VS. Note that partial NGEN can be set at crossgen time in addition to setting the bit during IBC merge, so not setting the bit at merge time does not preclude the use of partial NGEN later on.

[tmat]

Sure, but we do not crossgen assemblies that target .NET Framework (those that are inserted to VS).

I think we can easily support full ngen by adding a property that removes the -partialNGEN flag.

Currently we have bool ApplyPartialNgenOptimization and bool EnablePartialNgenOptimization.
We can rename to NgenOptimization with values { full, partial, empty } and EnableNgenOptimization, respectively to make the names more fitting.

[brianrob]

Seems completely reasonable. Is this something that you can do?

[tmat]

Yup. When do you need it?

[brianrob]

1-2 weeks from now would be awesome. Thanks.

[brianrob]

@tmat are you able to make this change? Thanks.

[tmat]

Yes, I'm planning on doing it. Just waiting for Preview 3 to wrap up.

[brianrob]

Cool. Do you have an ETA?

[tmat]

Would EOW work?

[brianrob]

Absolutely. Thanks.

[tmat]

@brianrob Can we close this? You can now specify full/partial via ApplyNgenOptimization property.

[brianrob]

Yes, thanks again for doing this.