[llvm-dev] Updating RegMask inline

[vivek pandya via llvm-dev]

On Sat, May 28, 2016 at 7:46 AM, Mehdi Amini <mehdi.amini at apple.com> wrote:

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> Sent from my iPhone
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> On May 27, 2016, at 7:02 PM, vivek pandya <vivekvpandya at gmail.com> wrote:
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> On Sat, May 28, 2016 at 7:29 AM, Matthias Braun <matze at braunis.de> wrote:
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>> On May 27, 2016, at 6:55 PM, vivek pandya via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
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>> On Sat, May 28, 2016 at 12:23 AM, vivek pandya <vivekvpandya at gmail.com>
>> wrote:
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>>> On Sat, May 28, 2016 at 12:21 AM, Mehdi Amini <mehdi.amini at apple.com>
>>> wrote:
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>>>> > On May 27, 2016, at 11:49 AM, vivek pandya <vivekvpandya at gmail.com>
>>>> wrote:
>>>> >
>>>> > Hello Mentors,
>>>> >
>>>> > I have completed writing simple register mask calculator pass, an
>>>> immutable pass that stores RegMasks and provides API to query them, and a
>>>> target specific pass for X86 target which currently iterates through all MI
>>>> in given MF and if a call instruction is found then it quires for RegMask
>>>> to Immutable pass and prints which registers are clobbered and preserved as
>>>> per actual register allocation for callee function.
>>>> >
>>>> > So now I need to update RegMask for call instruction, so as per our
>>>> previous discussion on IRC if we add a method to update RegMask, Do we have
>>>> to do it in target specific way? Is it possible to have RegMask at fixed
>>>> position in Operands array in MI? Also provide some more details on
>>>> updating cached RegMask in various other class.
>>>>
>>>> Add a method "setOperandMask()" in class MachineOperand, and then when
>>>> you find a call you just walk all the operands till you find one which
>>>> "isRegMask()" at which point you can update it.
>>>>
>>>> Ok.
>>>
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>> Is it ok to add "setRegMaskOperand()" in class MI and looping through
>> operands to find RegMask is also included in method ?
>> -Vivek
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>> I expect your code to be the only user of such a function  so I would not
>> add it to MachineInstr but keep the code local in your pass for now (you
>> can add a static helper function in the .cpp file of your pass).
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>> But Operands are private to MI so It should go into MI or some other
> tricks like Friend Function ?
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> Not sure what you mean by private here, can't you iterate the operands?
> I'd expect you to iterate the operands till op->isRegMask() is true, then
> you just have to update the regmask inside the operand. I think I already
> pointed you this, what's not working? Why are you trying to find a
> different solution?
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> I got the previous idea, I just did not see iterators and I just thought
to move iteration to find RegMask from user code to MI but now it is
clear.  Sorry for that : (

Vivek

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> Vivek
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>> - Matthias
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