[llvm-dev] Misuse of MRI.getRegClass in multiple target's FastIsel code

[Craig Topper via llvm-dev]

Yeah I just noticed that. Thanks!

~Craig

On Fri, Sep 23, 2016 at 8:30 AM, Krzysztof Parzyszek via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> MachineRegisterInfo::getRegClass does take a virtual register and returns
> the TargetRegisterClass of that register. You're thinking about
> TargetRegisterInfo::getRegClass.
>
> -Krzysztof
>
>
> On 9/23/2016 10:20 AM, Craig Topper via llvm-dev wrote:
>
>> This code or subtle variations of it appears in multiple targets. It
>> tries to convert from a register to a register class using getRegClass,
>> but getRegClass is really supposed to take a register class enum value
>> and get the register class object for it. It doesn't convert a register
>> to a class. In fact there's not always a single or canonical class for a
>> given register.
>>
>> What is the right way to do this?
>>
>>     unsigned SrcReg = Reg + VA.getValNo();
>>     unsigned DestReg = VA.getLocReg();
>>     // Avoid a cross-class copy. This is very unlikely.
>>     if (!MRI.getRegClass(SrcReg)->contains(DestReg))
>>       return false;
>>
>>
>> ~Craig
>>
>>
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>>
>>
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