[LLVMdev] Regression in 3.4's register allocator?

Evan Cheng evan.cheng at apple.com
Mon Jun 16 10:13:39 PDT 2014


Hi Niklas,

The attached patch has nothing to do with register allocation. r206094 changes how cpu auto-detection is done. I believe it's now the responsibility of the tools (e.g. llc) to detect the cpu. My guess is the proper fix is on the RoboVM side to handle the change.

Jim, can you confirm?

Evan

On Jun 1, 2014, at 1:45 PM, Niklas Therning <niklas at therning.org> wrote:

> I think we have located the revision which fixes this regression: r206094 (or commit 6bb00df in llvm-mirror on GitHub). I have attached a patch which can be applied to the current release_34 branch (tested against the release_34 branch in llvm-mirror). With this patch the attached reg-alloc-test.ll file doesn't fail with the "LLVM ERROR: ran out of registers during register allocation" error any longer. I haven't run any llvm tests to make sure this patch doesn't break anything else but as far as I can see it doesn't at least break anything when used in RoboVM.
> 
> Is it too late to get this into 3.4.2? Is there anything else I can do to make it easier for you to include this patch in 3.4.2 or the next possible point release?
> 
> 
> 
> On Wed, May 14, 2014 at 3:25 PM, Renato Golin <renato.golin at linaro.org> wrote:
> On 14 May 2014 14:15, Niklas Therning <niklas at therning.org> wrote:
> > I can confirm that this regression has been fixed in trunk. Should I report
> > this as a bug in 3.4?
> 
> The 3.4.2 release is coming, you might want to consider finding the
> patches responsible for the fix and proposing it for back-porting.
> 
> Please email Tom (cc'd) if you end up with a proposal.
> 
> cheers,
> --renato
> 
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