llvm dev - Jun 2015 - [LLVMdev] Replacing a Reg MachineOperand with a non-Reg MachineOperand?

Tom,

  My current example is a global address; however, it could be any operand
in theory. The arch allows for direct mem op support for ex instructions,
so it could be any type of address or any type of imm or any type of
register.

  For example, we are using intrinsics for some instructions since LLVM
does not support them. Table gen does not allow for matching to direct mem
op because the intrinsics are calls, so registers are setup for the call
parameters. So we end up with something like:

  mov @a, r0
  abs r0, r1

In our arch, we should be able to do 'abs @a, r1'. So since the
intrinsics
won't match properly in the tblgen we're looking at doing a peephole
where
we want to replace the operand 'r0' with @a and remove the 'mov @a,
r0'
instruction, so it would look like:

  abs @a, r1

Thanks.

ps. We could add these operators to LLVM instead of using intrinsics but
that also introduces a lot of dev cost and maintenance cost and some other
technical issues, but then we could have the operators match in the tblgen.
We are looking to avoid this, we thought a simple peephole would do the
trick instead.

On Tue, Jun 16, 2015 at 9:57 AM, Tom Stellard <tom at stellard.net> wrote:
> On Mon, Jun 15, 2015 at 10:16:47PM -0400, Ryan Taylor wrote:
> > I have a MachineOperand that could be something other than a Reg: mem,
> > global address, imm, etc...
> >
> > I want to replace a reg MachineOperand with this non-reg
MachineOperand.
> >
> > I've tried a few different things, but it doesn't seem like
there is some
> > simple functionality to do this?
> >
> > "RemoveOperand" and "addOperand" does not work.
> > There doesn't seem to be a valid "ChangeTo..." function
for this.
> >
> >
>
> What type of operand do you want to change it to?  If there is no
> "ChangeTo..." function for the new type, I think the best thing
to do
> would be to add a new "ChangeTo..." function to handle the new
type.
>
> -Tom
>
> > What's the best way to do this without tearing down the
instructions and
> > using BuildMI?
> >
> > Thanks.
>
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
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So I have this for ChangeToGlobalAddress(const GlobalValue *GV):

...
OpKind = MO_GlobalAddress;
Contents.OffsetedInfo.Val.GV = GV;

and then I use the function like this:

MI->getOperand(1).ChangeToGlobalAddress(MII->getOperand(1).getOperand.getGlobal());

The operand ends up being replaced with the global; however, it's also
adding a large constant immediate value with it.

For example, instead of <ga:@a> I end up with <ga:@a+2147483653> and
instead of <ga:@a+100> I end up with <ga:@a+214748564>

What might I be doing wrong?

Thanks.

On Tue, Jun 16, 2015 at 10:12 AM, Ryan Taylor <ryta1203 at gmail.com>
wrote:
> Tom,
>
>   My current example is a global address; however, it could be any operand
> in theory. The arch allows for direct mem op support for ex instructions,
> so it could be any type of address or any type of imm or any type of
> register.
>
>   For example, we are using intrinsics for some instructions since LLVM
> does not support them. Table gen does not allow for matching to direct mem
> op because the intrinsics are calls, so registers are setup for the call
> parameters. So we end up with something like:
>
>   mov @a, r0
>   abs r0, r1
>
> In our arch, we should be able to do 'abs @a, r1'. So since the
intrinsics
> won't match properly in the tblgen we're looking at doing a
peephole where
> we want to replace the operand 'r0' with @a and remove the 'mov
@a, r0'
> instruction, so it would look like:
>
>   abs @a, r1
>
> Thanks.
>
> ps. We could add these operators to LLVM instead of using intrinsics but
> that also introduces a lot of dev cost and maintenance cost and some other
> technical issues, but then we could have the operators match in the tblgen.
> We are looking to avoid this, we thought a simple peephole would do the
> trick instead.
>
> On Tue, Jun 16, 2015 at 9:57 AM, Tom Stellard <tom at stellard.net>
wrote:
>
>> On Mon, Jun 15, 2015 at 10:16:47PM -0400, Ryan Taylor wrote:
>> > I have a MachineOperand that could be something other than a Reg:
mem,
>> > global address, imm, etc...
>> >
>> > I want to replace a reg MachineOperand with this non-reg
MachineOperand.
>> >
>> > I've tried a few different things, but it doesn't seem
like there is
>> some
>> > simple functionality to do this?
>> >
>> > "RemoveOperand" and "addOperand" does not
work.
>> > There doesn't seem to be a valid "ChangeTo..."
function for this.
>> >
>> >
>>
>> What type of operand do you want to change it to?  If there is no
>> "ChangeTo..." function for the new type, I think the best
thing to do
>> would be to add a new "ChangeTo..." function to handle the
new type.
>>
>> -Tom
>>
>> > What's the best way to do this without tearing down the
instructions and
>> > using BuildMI?
>> >
>> > Thanks.
>>
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>>
>
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Hey Ryan,

You end with a large constant immediate offset value because the register
operand stores the register id in a union together with the offset that's
used by the global address operand.

Just add 'setOffset(0)' to your change method and that should solve your
problem.

2015-06-16 9:15 GMT-07:00 Ryan Taylor <ryta1203 at gmail.com>:
> So I have this for ChangeToGlobalAddress(const GlobalValue *GV):
>
> ...
> OpKind = MO_GlobalAddress;
> Contents.OffsetedInfo.Val.GV = GV;
>
> and then I use the function like this:
>
>
>
MI->getOperand(1).ChangeToGlobalAddress(MII->getOperand(1).getOperand.getGlobal());
>
> The operand ends up being replaced with the global; however, it's also
> adding a large constant immediate value with it.
>
> For example, instead of <ga:@a> I end up with
<ga:@a+2147483653> and
> instead of <ga:@a+100> I end up with <ga:@a+214748564>
>
> What might I be doing wrong?
>
> Thanks.
>
> On Tue, Jun 16, 2015 at 10:12 AM, Ryan Taylor <ryta1203 at gmail.com>
wrote:
>
>> Tom,
>>
>>   My current example is a global address; however, it could be any
>> operand in theory. The arch allows for direct mem op support for ex
>> instructions, so it could be any type of address or any type of imm or
any
>> type of register.
>>
>>   For example, we are using intrinsics for some instructions since LLVM
>> does not support them. Table gen does not allow for matching to direct
mem
>> op because the intrinsics are calls, so registers are setup for the
call
>> parameters. So we end up with something like:
>>
>>   mov @a, r0
>>   abs r0, r1
>>
>> In our arch, we should be able to do 'abs @a, r1'. So since the
>> intrinsics won't match properly in the tblgen we're looking at
doing a
>> peephole where we want to replace the operand 'r0' with @a and
remove the
>> 'mov @a, r0' instruction, so it would look like:
>>
>>   abs @a, r1
>>
>> Thanks.
>>
>> ps. We could add these operators to LLVM instead of using intrinsics
but
>> that also introduces a lot of dev cost and maintenance cost and some
other
>> technical issues, but then we could have the operators match in the
tblgen.
>> We are looking to avoid this, we thought a simple peephole would do the
>> trick instead.
>>
>> On Tue, Jun 16, 2015 at 9:57 AM, Tom Stellard <tom at
stellard.net> wrote:
>>
>>> On Mon, Jun 15, 2015 at 10:16:47PM -0400, Ryan Taylor wrote:
>>> > I have a MachineOperand that could be something other than a
Reg: mem,
>>> > global address, imm, etc...
>>> >
>>> > I want to replace a reg MachineOperand with this non-reg
>>> MachineOperand.
>>> >
>>> > I've tried a few different things, but it doesn't seem
like there is
>>> some
>>> > simple functionality to do this?
>>> >
>>> > "RemoveOperand" and "addOperand" does not
work.
>>> > There doesn't seem to be a valid "ChangeTo..."
function for this.
>>> >
>>> >
>>>
>>> What type of operand do you want to change it to?  If there is no
>>> "ChangeTo..." function for the new type, I think the best
thing to do
>>> would be to add a new "ChangeTo..." function to handle
the new type.
>>>
>>> -Tom
>>>
>>> > What's the best way to do this without tearing down the
instructions
>>> and
>>> > using BuildMI?
>>> >
>>> > Thanks.
>>>
>>> > _______________________________________________
>>> > LLVM Developers mailing list
>>> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>
>>>
>>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
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