[LLVMdev] forcing two instructions to be together

Owen Anderson resistor at mac.com
Tue Sep 17 15:52:25 PDT 2013

+the list again
On Sep 17, 2013, at 3:48 PM, reed kotler <rkotler at mips.com> wrote:

> On 09/17/2013 03:46 PM, Owen Anderson wrote:
>> On Sep 17, 2013, at 3:08 PM, reed kotler <rkotler at mips.com> wrote:
>>> Is there any way, except for using bundles, to force two instructions to be sequentially executed?
>> What level of codegen are you working at?  There are various mechanisms that can be applied, depending on exactly what the constraints are that you need to preserve.
>> —Owen
> I have two machine instructions that I need to be together.
>  BuildMI(MBB, I, DL, TII.get(Mips::LiRxImmAlignX16), V0)
>    .addExternalSymbol("_gp_disp", MipsII::MO_ABS_HI);
>  BuildMI(MBB, I, DL, TII.get(Mips::AddiuRxPcImmX16), V1)
>    .addExternalSymbol("_gp_disp", MipsII::MO_ABS_LO);
> It's in Mips16ISelDagToDag.cpp
> these two have to be together because they are both part of a complex pc relative calculation.
> I have not used bundles yet and was just looking for an easy way to join these two.

Bundles is one way you can go.  Another is to use a pseudo instruction that is broken up immediately before (or during!) MC emission.


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