Discontinue support for IA32 architecture

[alexmarkov]

IA32 architecture is somewhat special in Dart VM:

• AOT compilation is not supported on IA32.
• Type testing stubs are not supported on IA32.
• Due to a small number of registers, IA32 often has a custom implementation of various stubs or custom code generation patterns which are sufficiently different from other architectures.

Supporting IA32 carries additional burden when adding new features. At the same time, usage of IA32 declines over time.

We should consider if it is still useful to support IA32 architecture in the future versions of Dart, deprecate and eventually drop IA32.

/cc @mit-mit @a-siva @mraleph @mkustermann

[mit-mit]

cc @Hixie @tvolkert any known big Flutter uses of this?

[aam]

I thought android simulator used for internal testing only supports x86

[a-siva]

I thought android simulator used for internal testing only supports x86

The last time I checked it seemed like they were all migrating to use x64 simulators, maybe @xster has more information on this.

[tvolkert]

/cc @zanderso

[zanderso]

@a-siva right, AFAIK we're only keeping support for IA32 around for internal simulator testing. We can start the process to drop it as soon as it's no longer needed there.

[Hixie]

cc @khyati82

[Hixie]

(I'm fine with removing IA32 support.)

[mraleph]

It does seem that there is some dependency on IA32 target (e.g. on Windows) and some companies maintaining it as a target outside of Flutter tree, see comments on flutter/flutter#37777

I think we could try to find a way to keep IA32 alive, but potentially not very performant.

[khyati82]

Based on IA32 usage internally, we are going to revisit this issue once that migration is done.

[athomas]

Given that it seems unlikely that we will invest in adding support for Windows IA32 to Flutter based on the linked issue, is it really worth it to carry around this support in Dart? Assuming someone still needs to use Dart on Windows IA32, they can continue to use old versions until they are ready to upgrade. If you're on Windows XP/IA32 (one comment on the thread mentions Windows XP being widely used by their customers), you're already using old versions of most other software.