[PATCH] D153774: [ARM] Generate out-of-line jump tables for XO without 32-bit branch

[Eli Friedman via Phabricator via llvm-commits]

efriedma accepted this revision.
efriedma added a comment.
This revision is now accepted and ready to land.

Oh, I didn't remember JUMPTABLE_INSTS was a thing.  This is making more sense now; Thumb2/armv8m.base defaults to jumping to a table of jumps, which works fine with execute-only, but Thumb1 (and apparently ARM-mode) loads offsets from a table instead, which doesn't work with execute-only.  So to make Thumb1 work, you force the table to be emitted out-of-line.

That makes sense, but depending how much we care, there are probably better sequences.  We can use "bl" as a 32-bit branch on Thumb1, like we do in other places.  And we can then compress those 32-bit branches to 16-bit branches if the offsets aren't too big.

If you just care about getting it working, this is okay as-is.  LGTM


Repository:
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https://reviews.llvm.org/D153774