[beta] box large variants in MIR

[arielb1]

Beta backport of #41926.

Operand: 72 -> 24 B
Statement: 192 -> 96 B
Terminator: 256 -> 112 B
librustc translation memory usage: 1795 -> 1669 MB

next step would be interning lvalues, I suppose?

[rust-highfive]

r? @nikomatsakis

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[rust-highfive]

Warning

• Pull requests are usually filed against the master branch for this repo, but this one is against beta. Please double check that you specified the right target!

[nikomatsakis]

@bors r+

[bors]

📌 Commit 74fe27f has been approved by nikomatsakis

[aidanhs]

(not a legit PR build failure, it just failed to clone (#42117) on the OSX builder which wouldn't do anything anyway. Nothing to to retry since bors hasn't had a look yet)

[aidanhs]

(realised I have the power to retry jobs, so I did so and all is green)

[brson]

@bors p=1

[bors]

⌛ Testing commit 74fe27f with merge f40fad5...

[bors]

💔 Test failed - status-travis

[alexcrichton]

@bors: r=nikomatsakis

[bors]

📌 Commit ea239f2 has been approved by nikomatsakis

[bors]

⌛ Testing commit ea239f2 with merge cf77445...

[bors]

💔 Test failed - status-appveyor

[alexcrichton]

@bors: retry

• ar.exe error fixed on master

[bors]

⌛ Testing commit ea239f2 with merge e9f90f7...

[bors]

💔 Test failed - status-travis

[Mark-Simulacrum]

@bors retry

• Spurious segfault in tests for musl #38618 musl segfault

[bors]

⌛ Testing commit ea239f2 with merge 4644612...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 4644612 to beta...