[LLVMdev] LLVM pass question

Reed Kotler rkotler at mips.com
Wed Mar 27 11:17:32 PDT 2013

This seems to work okay.

I register both the Mips16 and non Mips16 passes of the instruction 
selector and then those return false if they are not supposed to be running.

Make-check at least passes in this case.

So in principle turn on the dual mode now and debug whatever misc is left.

For this I insert another pass before the mips16 and non mips16 passes.

On 03/27/2013 10:19 AM, Reed Kotler wrote:
> What I am thinking of now is to just register the MIPS116 and MIPS32
> DAGToDAGISel passes and then within run on machine function, I can just
> return if the current mode indicates that mips16 is needed for example,
> so the run on machine function for Mips32 would return immediately.
> On 03/27/2013 10:05 AM, Reed Kotler wrote:
>> I guess another way to do this is to just register both passes for
>> mips16 and mips32 and have them return immediately if it is not their
>> turn to run.
>> On 03/27/2013 08:58 AM, Reed Kotler wrote:
>>> I'm implementing this ability to switch between mips16 and mips32 on a
>>> per function basis.
>>> One issue that I've run into is regarding the DAGToDAGIsel pass.
>>> We have a different subclass for mips16 and non mips16 ( conceivably
>>> later there could be a separate one for micromips).
>>> I need to run a different pass depending on whether it's mips16 or
>>> mips32.
>>> My initial plan was to create a dummy ModuleDAGToDAGIsel whose sole
>>> purpose in it's run machine function was to decide which one of these
>>> to run and then call an appropriate DAGToDAGIIsel but I'm running into
>>> some issue where that class wants to be started up by the pass manager
>>> and not another pass.
>>> So now I'm think that maybe I should have either:
>>> 1) The ModuleDAGToDAGIsel pass add another pass.
>>> 2) Maybe create two passes, one for Mips16 and one for Mips32 and have
>>> them be dependent on the ModuleDAGToDAGISel pass and then turn them on
>>> or off depending on which one needs to be run for this function.
>>> I'm reading the pass code now to understand this better but thought that
>>> someone might know the answer.
>>> Tia.
>>> Reed

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