Merging r367753:

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r367753 | nikic | 2019-08-03 08:47:23 +0200 (Sat, 03 Aug 2019) | 12 lines

[Thumb] Fix invalid symbol redefinition due to duplicated jumptable (PR42760)

Fix for https://bugs.llvm.org/show_bug.cgi?id=42760. A tBR_JTr
instruction is duplicated by tail duplication, which results in
the same jumptable with the same label being emitted twice.

Fix this by marking tBR_JTr as not duplicable. The corresponding
ARM/Thumb instructions are already marked as not duplicable.
Additionally also mark tTBB_JT and tTBH_JT to be consistent with
Thumb2, even though this shouldn't be strictly necessary.

Differential Revision: https://reviews.llvm.org/D65606
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llvm-svn: 367808