llvm dev - Nov 2015 - DFAPacketzer, Hexagon and bundles with 1 instruction

I'm trying to figure out how Hexagon (I'm using it as an example for my
own
VLIW) is handling bundles with 1 instruction, but I don't quite get it.
Here is the code that I have for a endPacket

// endPacket - End the current packet, bundle packet instructions and reset
// DFA state.
void VLIWPacketizerList::endPacket(MachineBasicBlock *MBB,
                                         MachineInstr *MI) {
  if (CurrentPacketMIs.size() > 1) {
    MachineInstr *MIFirst = CurrentPacketMIs.front();
    finalizeBundle(*MBB, MIFirst, MI);
  }
  CurrentPacketMIs.clear();
  ResourceTracker->clearResources();
}

Based on this, it looks like packets with one instruction are not finalized
(finalizeBundle is the one which inserts a BUNDLE instruction). So what
happens with packets that have only 1 instruction? Is there a separate pass
that creates a bundle from a single instruction?

Any help is appreciated.

-- 
R
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On 11/17/2015 3:30 PM, Rail Shafigulin via llvm-dev
wrote:
>
> Is there a separate pass that creates a bundle from a single instruction?
No. An instruction on its own is equivalent to a bundle with that 
instruction only. Also, a BUNDLE must have at least 2 instructions.

-Krzysztof

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
hosted by The Linux Foundation

> No. An instruction on its own is equivalent to a bundle with that
> instruction only. Also, a BUNDLE must have at least 2 instructions.
>
> -Krzysztof
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by The Linux Foundation
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

I'm a little confused. If a bundle is supposed to have at least 2
instructions, what is the point of
VLIWPacketzierList::isSoloInstruction(...)? Say we have an instruction that
can't be bundled with anything, how would one form a packet from it?

-- 
R
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