[LLVMdev] Register Alias Sets

Christopher Lamb christopher.lamb at gmail.com
Sat Apr 7 08:25:42 PDT 2007

On Apr 6, 2007, at 4:51 PM, David Greene wrote:

> I notice that in X86GenRegisterInfo.inc, the AliasSets do not
> include the register being queried.  For example:
>    const unsigned RAX_AliasSet[] = { X86::EAX, X86::AX, X86::AL,  
> X86::AH,
> 0 };
>    const unsigned EAX_AliasSet[] = { X86::RAX, X86::AX, X86::AL,
> X86::AH, 0 };
> This makes it hard to do set comparisons.  RAX and EAX really have
> equivalent alias sets but one wouldn't know that from these  
> definitions.

Does it really make it that hard to do set comparisons? The sets are  
themselves indexed by the register that the set applies to. If you  
have the index then you can explicitly add this to the set for your  

Christopher Lamb

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