[LLVMdev] basic block missing after MachineInstr packetizing

[Andrew Trick]

On Jan 8, 2014, at 6:12 PM, 杨勇勇 <triple.yang at gmail.com> wrote:

> Sergei, Thank you for your attention.
> 
> My target is a custom VLIW DSP. I am not sure dependency dag is correct when it gets scheduled and packetized. Months ago, I submitted a bug at http://llvm.org/bugs/show_bug.cgi?id=17894 which explained more details.
> 
> I am not sure my understanding of this bug is proper, but modified my local codes this way and it works for my target when scheduling and packetizing.
> 
> Well why this problem does not occur for Hexagon target?

FYI: if there is a bug in finalizeBundle() one possible fix is not calling it. Nothing in the MachineIR requires finalizeBundle to be called, bundles are perfectly valid without it. It is only there for legacy reasons because some targets want to see the extra BUNDLE marker with duplicate MachineOperands.

-Andy

> 
> Regards.
> 
> 
> 2014/1/9 Sergei Larin <slarin at codeaurora.org>
> Yang,
> 
>  
> 
>   There is not enough info here to understand what is going wrong – what is your target? Is dependency dag correct going into scheduling and packetization?
> 
>  
> 
> Sergei
> 
>  
> 
> ---
> 
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
> 
>  
> 
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of ???
> Sent: Sunday, November 10, 2013 8:31 PM
> To: LLVM-Dev ‎[llvmdev at cs.uiuc.edu]‎
> Subject: [LLVMdev] basic block missing after MachineInstr packetizing
> 
>  
> 
> Hi, all,
> 
>  
> 
> When I schedule machine instructions in a VLIW way and packetize them, a problem is encountered, and I will show it use a simplified case as follows.
> 
>  
> 
> ############ original instruction sequence
> 
> ...
> 
> insn1
> 
> ...
> 
> jump  LBB0_xx
> 
> ...
> 
> LBB0_xx:
> 
> ...
> 
>  
> 
> ############ expected instruction sequence after scheduling and packetizing
> 
> insn1; jump LBB0_xx
> 
> ...
> 
> LBB0_xx:
> 
> ...
> 
>  
> 
> ############ generated instruction sequence
> 
> insn1; jump LBB0_xx
> 
> ...
> 
> #BB#xx:
> 
> ...
> 
>  
> 
> BasicBlock BB#xx is commented out when insn1 and "jump LBB0_xx" is bundled.
> 
> I guess the reference to LBB0_xx is deconstructed when insn1 and LBB0_xx are packetized together thus BB#xx is commented out.
> 
>  
> 
> What should we do if the reference to LBB0_xx has to be maintained?
> 
>  
> 
> Thanks ahead!
> 
> 
> --
> 
> 杨勇勇 (Yang Yong-Yong)
> 
> 
> 
> 
> -- 
> 杨勇勇 (Yang Yong-Yong)
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