[LLVMdev] proposal to simplify isel/asmprinter interaction with globals

Evan Cheng evan.cheng at apple.com
Mon Jun 22 11:49:07 PDT 2009

On Jun 20, 2009, at 7:30 PM, Chris Lattner wrote:

> My proposed fix for this is to add an 'unsigned char' slot to
> MachineOperand that holds a target-specific enum value.  The code in
> asmprinter would be reduced to:
> switch (theoperandenum) {
> case X86::MO_Flag_non_lazy_ptr:
>   O << "$non_lazy_ptr";
>   break;
> case X86::MO_Flag_TLSGD:
>   O << "@TLSGD";
>   break;
> case X86::MO_Flag_NTPOFF:
>   O << "@NTPOFF";
>   break;
> etc.  The possible set of suffixes and modifiers are all target-
> specific, so the main code generator would just pass them through (as
> it does now).
> Does anyone have any objections to this?

Can you reorg MachineOperand fields while you are at it? :-) Right now  
each MachineOperand uses 8 bits for type, followed by 5 bits for  
various flags, then a whole 8-bit for subreg.  If we use just 3-bit  
for subreg (should be enough?), the target independent part will just  
take up 16-bits and leave plenty of room for target flags.


> -Chris
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