[PATCH] D35816: [Greedy RegAlloc] Add logic to greedy reg alloc to avoid bad eviction chains

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet requested changes to this revision.
qcolombet added a comment.
This revision now requires changes to proceed.

Hi,

The greedy allocator is already very complicated and I am not sure the additional complexity of the eviction track is worth it.
Is it something that could be cleaned up in machine copy propagation? The problem is very local so that sounds doable.

I will have a closer look to the patch because fixing the problem from the start is obviously better that patching up later, but given how rare that problem is I really believe exploring other, less complex avenue is interesting.

Cheers,
Quentin



================
Comment at: test/CodeGen/X86/bug26810.ll:1
+; RUN: llc < %s -march=x86 -regalloc=greedy | FileCheck %s
+; Make sure bad eviction sequence doesnt occur
----------------
Could you use a .mir test to make the test more robust?


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Comment at: test/CodeGen/X86/bug26810.ll:3
+; Make sure bad eviction sequence doesnt occur
+; XFAIL: *
+
----------------
That sounds wrong for a new test.

Testing should be positive as much as possible IMO.


Repository:
  rL LLVM

https://reviews.llvm.org/D35816