Mem2Reg: Fix lifetime completion for enum case values.

[eeckstein]

Enum types may have incomplete lifetimes in address form for trivial case values. When promoted to value form, they will end up with incomplete ossa lifetimes. Because we know that the incomplete enum values are trivial enum cases we complete their lifetimes with end_lifetime instead of destroy_value. This is especially important for Embedded Swift where we are not allowed to insert destroys which were not there before.

Fixes a compiler crash in Embedded Swift caused by de-virtualizing such an inserted destroy and ending up with a non-specialized generic function.

rdar://158807801

[eeckstein]

@swift-ci test

[eeckstein]

@swift-ci test windows

[nate-chandler]

Please add some specify_test tests that illustrate why this is an argument that should be passed into the utility rather than something that it should discover on its own for example by checking that a value is trivial.

[eeckstein]

I added a test.

that illustrate why this is an argument that should be passed into the utility rather than something that it should discover on its own for example by checking that a value is trivial.

This is not about the value being trivial. The utility cannot know that an end_lifetime should be used, because this is something only the caller (in this case mem2reg) knows: It needs to use end_lifetime because the incomplete values are (non-trivial) enums with a trivial or no payload.

[eeckstein]

@swift-ci test

[meg-gupta]

lgtm