search for: ccassigntoregwithshadow

Hi, all On the website, it says, CCAssignToRegWithShadow <registerList, shadowList> — similar to CCAssignToReg, but with a shadow list of registers I don't know when we should use CCAssignToRegWithShadow. Because I am not a architecture expert, please bear with my naive question. Take ARMCallingConv.td as an example, CCIfType<[i32], CC...

Hello >  I don't know when we should use CCAssignToRegWithShadow. Because > I am not a architecture expert, please bear with my naive question. > Take ARMCallingConv.td as an example, ARM is not good example :) Look into win64 calling convention. Shadow means if some register is allocated for incoming argument another one cannot be used for argument alloca...

...into xmm1, edx is marked as occupied, etc. I think ecx and xmm0 are physical different registers (not like ecx and cx), right? So why we cannot use xmm0 while ecx has been used? Is it just a rule or there are some considerations behind it? >> CCIfType<[i32], CCIfAlign<"8", CCAssignToRegWithShadow<[R0, R2], [R0, >> R1]>>> >> >>  If we assign a value to R0(R2), then what happen to R0(R1)? >It will be marked as occupied. If we assign to R0, then R0 is marked occupied. Is it a redundant statement? > Yes. On ARM shadowing used as a trick to ensure "r...