[llvm] r271925 - [MBP] Reduce code size by running tail merging in MBP.

[Haicheng Wu via llvm-commits]

Thank you for creating a bug for me, Diana.

If you have a reduced test case, please help me attach it to PR28049.  If not, I can work on it.

Do you think it is better for me to reapply r271925 but leave it turned off by default so that whoever tries to fix PR28049 does not need to rebase my reverted patch?

Best,

Haicheng

-----Original Message-----
From: Diana Picus [mailto:diana.picus at linaro.org] 
Sent: Wednesday, June 08, 2016 5:41 AM
To: Haicheng Wu <haicheng at codeaurora.org>
Cc: llvm-commits <llvm-commits at lists.llvm.org>; Renato Golin <renato.golin at linaro.org>; Tim Northover <t.p.northover at gmail.com>; james.molloy at arm.com
Subject: Re: [llvm] r271925 - [MBP] Reduce code size by running tail merging in MBP.

On 8 June 2016 at 08:44,  <haicheng at codeaurora.org> wrote:
> I am not an expert of Thumb2 backend.  Is it a bug of the 
> implementation of ReplaceTailWithBranchTo()?  Or BB#187 is mistakenly 
> treated as an IT block (no t2IT instruction)?  Or I should not call 
> tail merging after Block Placement for Thumb2 at all?

I'm not an expert either. I'll try to have a look, and I've also created a bug for it: https://llvm.org/bugs/show_bug.cgi?id=28049
If anyone feels like they have a better chance of fixing this, please go ahead :)

> I think Thumb2 cares the code size and my patch is beneficial to Thumb2.
> Please let me know what you think.

I think we should try to get it to work.

Diana