llvm dev - Feb 2021 - Can't call setTypeAction() on ValueTypeActions in a derived class from the TargetLoweringBase class

Hello.

     I would like to ask about what seems to be an API error in LLVM in the 
include/llvm/CodeGen/TargetLowering.h source file, in the class
TargetLoweringBase.
     We have the public method getValueTypeActions() that returns a constant of
type const
ValueTypeActionImpl. But the class ValueTypeActionImpl has the setter method 
setTypeAction(), which I need to use to make my Instruction Selection pass
succeed. More
exactly I need to give in my ISelLowering back end pass (otherwise I get error
"Do not
know how to promote this operator's operand!"):
          getValueTypeActions().setTypeAction(MVT::f16, TypeLegal));

     Note that in the last almost 2 years in
include/llvm/CodeGen/TargetLowering.h, in the
class TargetLoweringBase the access specifier of the data member:
         ValueTypeActionImpl ValueTypeActions;
      was changed from protected to private, and the private specifier disallows
me to use
the setTypeAction() method in my back end class derived from the class
TargetLowering,
which is itself derived from class TargetLoweringBase.

     Therefore, I propose to define method getValueTypeActions() without const
specifiers
like this:
           ValueTypeActionImpl &getValueTypeActions() {
             return ValueTypeActions;
           }
     Am I correct to propose this? Or is there another way to use the method
setTypeAction()?

   Thank you very much,
     Alex

On 27 Feb 2021, at 15:03, Alex Susu via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
>  Hello.
> 
>     I would like to ask about what seems to be an API error in LLVM in the
include/llvm/CodeGen/TargetLowering.h source file, in the class
TargetLoweringBase.
>     We have the public method getValueTypeActions() that returns a constant
of type const ValueTypeActionImpl. But the class ValueTypeActionImpl has the
setter method setTypeAction(), which I need to use to make my Instruction
Selection pass succeed. More exactly I need to give in my ISelLowering back end
pass (otherwise I get error "Do not know how to promote this operator's
operand!"):
>         getValueTypeActions().setTypeAction(MVT::f16, TypeLegal));
> 
>     Note that in the last almost 2 years in
include/llvm/CodeGen/TargetLowering.h, in the class TargetLoweringBase the
access specifier of the data member:
>         ValueTypeActionImpl ValueTypeActions;
>      was changed from protected to private, and the private specifier
disallows me to use the setTypeAction() method in my back end class derived from
the class TargetLowering, which is itself derived from class TargetLoweringBase.
> 
>     Therefore, I propose to define method getValueTypeActions() without
const specifiers like this:
>          ValueTypeActionImpl &getValueTypeActions() {
>            return ValueTypeActions;
>          }
>     Am I correct to propose this? Or is there another way to use the method
setTypeAction()?
The definition of whether a type is legal is whether the target has a
register class for it; if you want the type to be legal you need to
define one, then TargetLoweringBase::computeRegisterProperties won't
define the type as illegal.

Jess

Hello.
     I don't have a register class for my target for the f16 type (neither
for the i32
type). What I do is actually emulate the LLVM IR operations for the f16 type in
my back
end class that inherits the SelectionDAGISel class.
     However, for everything to work OK I have to give:
       getValueTypeActions().setTypeAction(MVT::f16, TypeLegal));

     Now maybe I can give a different LegalizeTypeAction like TypePromoteFloat
instead of
TypeLegal. But then I need to have as I said in the previous email the
possibility to call:
       getValueTypeActions().setTypeAction(MVT::f16, TypeLegal));
     But this call is no longer possible in the latest LLVM. And this issue
seems wrong to me.

   Thank you,
     Alex

On 2/28/2021 9:04 PM, Jessica Clarke wrote:
> On 27 Feb 2021, at 15:03, Alex Susu via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>>   Hello.
>>
>>      I would like to ask about what seems to be an API error in LLVM in
the include/llvm/CodeGen/TargetLowering.h source file, in the class
TargetLoweringBase.
>>      We have the public method getValueTypeActions() that returns a
constant of type const ValueTypeActionImpl. But the class ValueTypeActionImpl
has the setter method setTypeAction(), which I need to use to make my
Instruction Selection pass succeed. More exactly I need to give in my
ISelLowering back end pass (otherwise I get error "Do not know how to
promote this operator's operand!"):
>>          getValueTypeActions().setTypeAction(MVT::f16, TypeLegal));
>>
>>      Note that in the last almost 2 years in
include/llvm/CodeGen/TargetLowering.h, in the class TargetLoweringBase the
access specifier of the data member:
>>          ValueTypeActionImpl ValueTypeActions;
>>       was changed from protected to private, and the private specifier
disallows me to use the setTypeAction() method in my back end class derived from
the class TargetLowering, which is itself derived from class TargetLoweringBase.
>>
>>      Therefore, I propose to define method getValueTypeActions()
without const specifiers like this:
>>           ValueTypeActionImpl &getValueTypeActions() {
>>             return ValueTypeActions;
>>           }
>>      Am I correct to propose this? Or is there another way to use the
method setTypeAction()?
> 
> The definition of whether a type is legal is whether the target has a
> register class for it; if you want the type to be legal you need to
> define one, then TargetLoweringBase::computeRegisterProperties won't
> define the type as illegal.
> 
> Jess
>