Support 16-bit pointers in MIR

[shepmaster]

No description provided.

[rust-highfive]

r? @Aatch

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[shepmaster]

This seems a bit suspicious to me as my local AVR work is based on 4b240fe, which AFAICT shouldn't have MIR enabled by default. Nonetheless, I was getting assertions in this code. Anything to be worried about here?

[Aatch]

@shepmaster we always build the MIR, it's just not used for code generation by default yet, so it's not surprising that you got an assertion.

[shepmaster]

In relation to #33460.

[shepmaster]

we always build the MIR

@Aatch ah, good to know. Do you think that I'm likely to have covered most of the MIR codebase then, purely by accident?

[Aatch]

@shepmaster grepping for sess.target.int_type in the librustc_mir and librustc_trans/mir folders would probably point to likely locations.

[shepmaster]

Good call. I've done that (and uint_type) and didn't find any new, obvious holes. However, I realized I could enable MIR and see what happens. Let me do that before this gets merged.

[shepmaster]

@Aatch I've compiled libcore to LLVM-IR with -Z orbit and found this additional aspect. It touches a bit more code, but I think the readability gained from the new function is a win!

[Aatch]

Theres a couple tidy errors, but looks good to me otherwise.

[shepmaster]

@Aatch tidy issues addressed.

[eddyb]

@bors r=Aatch

[bors]

📌 Commit 1858cfb has been approved by Aatch

[bors]

⌛ Testing commit 1858cfb with merge f80ff7d...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-32cross-opt, auto-linux-64-cargotest, auto-linux-64-cross-armhf, auto-linux-64-cross-armsf, auto-linux-64-cross-freebsd, auto-linux-64-cross-netbsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-cross-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-mir, auto-win-msvc-64-opt-rustbuild