[LLVMdev] No more TargetFlags on MO_Register MachineOperands

[Owen Anderson]

On Aug 22, 2012, at 11:34 AM, "Villmow, Micah" <Micah.Villmow at amd.com> wrote:

> 
> 
>> -----Original Message-----
>> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
>> On Behalf Of Owen Anderson
>> Sent: Tuesday, August 21, 2012 11:37 AM
>> To: Stellard, Thomas
>> Cc: llvmdev at cs.illinois.edu
>> Subject: Re: [LLVMdev] No more TargetFlags on MO_Register
>> MachineOperands
>> 
>> Tom,
>> 
>> The generally accepted way of achieving this is to leave the built-in
>> pattern on the instruction empty, and to use def : Pat constructs to
>> provide the default values.
>> 
>> def : Pat<(fceil R600_Reg32:$src), (CEIL R600_Reg32:$src, (i32 0))>;
>> 
> [Villmow, Micah] Doing this for every instruction is unrealistic.

Not particularly.  There are backends already in existence that make heavy use of it.  The key is that def : Pat constructs can take advantage of all of the same mechanisms for factoring out commonality that normal patterns can, including multiclasses and ComplexOperands.

--Owen