[PATCH] D78248: [RegisterCoalescer] Extend a subrange if needed when filling range gap

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


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Comment at: llvm/test/CodeGen/Hexagon/regalloc-coal-extend-short-subrange.mir:17
+body: |
+  bb.0:
+    successors: %bb.2(0x80000000)
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kparzysz wrote:
> kparzysz wrote:
> > arsenm wrote:
> > > Can you reduce this further?
> > Not by much if at all.  This is what I got from a bugpoint testcase that was reduced pretty much as far as it would go.
> I just tried removing some things (replacing function arguments with undefs), but the testcase stopped failing.
Reducing these kinds of thing is difficult and time consuming, but in my experience doable. One technique I've used before is dumping the MIR from the middle of the register coalescer before the final change that hits the verifier error (and a combination of manually coalescing some of the copies). If it's so fragile the test may not end up usefully stressing this situation in the future


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https://reviews.llvm.org/D78248