Add initial design document for EH WriteThru
Add initial design document for EH WriteThru

Document describes an initial approch to enregistering local variables
that live across EH flow.  Today the JIT forces all local vars that are live
across EH flow that kills all registers to live on the stack.  The transformation outlined ensures consistency on the stack across the EH kills but allows the enregistration with in either the normal flow of control or with in any EH handlers.

qiudesong/coreclr,tijoytom/coreclr,gkhanna79/coreclr,ragmani/coreclr,parjong/coreclr,sagood/coreclr,YongseopKim/coreclr,parjong/coreclr,wtgodbe/coreclr,wateret/coreclr,cshung/coreclr,wateret/coreclr,yeaicc/coreclr,dpodder/coreclr,yizhang82/coreclr,mskvortsov/coreclr,wateret/coreclr,JonHanna/coreclr,ruben-ayrapetyan/coreclr,pgavlin/coreclr,alexperovich/coreclr,kyulee1/coreclr,JonHanna/coreclr,jamesqo/coreclr,poizan42/coreclr,tijoytom/coreclr,wtgodbe/coreclr,AlexGhiondea/coreclr,mmitche/coreclr,jamesqo/coreclr,jamesqo/coreclr,mskvortsov/coreclr,cshung/coreclr,botaberg/coreclr,krytarowski/coreclr,qiudesong/coreclr,yeaicc/coreclr,krk/coreclr,russellhadley/coreclr,poizan42/coreclr,AlexGhiondea/coreclr,mskvortsov/coreclr,yizhang82/coreclr,cydhaselton/coreclr,mmitche/coreclr,AlexGhiondea/coreclr,parjong/coreclr,cmckinsey/coreclr,russellhadley/coreclr,krytarowski/coreclr,JonHanna/coreclr,pgavlin/coreclr,AlexGhiondea/coreclr,yeaicc/coreclr,yeaicc/coreclr,wtgodbe/coreclr,cydhaselton/coreclr,ragmani/coreclr,mskvortsov/coreclr,yeaicc/coreclr,mmitche/coreclr,ruben-ayrapetyan/coreclr,cydhaselton/coreclr,qiudesong/coreclr,AlexGhiondea/coreclr,rartemev/coreclr,yeaicc/coreclr,alexperovich/coreclr,parjong/coreclr,ragmani/coreclr,alexperovich/coreclr,YongseopKim/coreclr,pgavlin/coreclr,hseok-oh/coreclr,yizhang82/coreclr,yizhang82/coreclr,gkhanna79/coreclr,James-Ko/coreclr,wateret/coreclr,botaberg/coreclr,botaberg/coreclr,tijoytom/coreclr,cmckinsey/coreclr,sagood/coreclr,sagood/coreclr,poizan42/coreclr,JonHanna/coreclr,gkhanna79/coreclr,dpodder/coreclr,mmitche/coreclr,kyulee1/coreclr,sagood/coreclr,YongseopKim/coreclr,parjong/coreclr,James-Ko/coreclr,mskvortsov/coreclr,kyulee1/coreclr,pgavlin/coreclr,cmckinsey/coreclr,dpodder/coreclr,hseok-oh/coreclr,gkhanna79/coreclr,yeaicc/coreclr,kyulee1/coreclr,wtgodbe/coreclr,parjong/coreclr,JosephTremoulet/coreclr,russellhadley/coreclr,ragmani/coreclr,YongseopKim/coreclr,rartemev/coreclr,ruben-ayrapetyan/coreclr,JosephTremoulet/coreclr,cydhaselton/coreclr,ragmani/coreclr,JonHanna/coreclr,James-Ko/coreclr,jamesqo/coreclr,gkhanna79/coreclr,russellhadley/coreclr,YongseopKim/coreclr,qiudesong/coreclr,jamesqo/coreclr,dpodder/coreclr,YongseopKim/coreclr,dpodder/coreclr,botaberg/coreclr,botaberg/coreclr,poizan42/coreclr,cshung/coreclr,krytarowski/coreclr,krk/coreclr,krytarowski/coreclr,JonHanna/coreclr,botaberg/coreclr,russellhadley/coreclr,JosephTremoulet/coreclr,tijoytom/coreclr,dpodder/coreclr,cshung/coreclr,hseok-oh/coreclr,JosephTremoulet/coreclr,tijoytom/coreclr,James-Ko/coreclr,gkhanna79/coreclr,mmitche/coreclr,alexperovich/coreclr,rartemev/coreclr,poizan42/coreclr,rartemev/coreclr,wtgodbe/coreclr,James-Ko/coreclr,ruben-ayrapetyan/coreclr,pgavlin/coreclr,cmckinsey/coreclr,cmckinsey/coreclr,ruben-ayrapetyan/coreclr,krytarowski/coreclr,krytarowski/coreclr,AlexGhiondea/coreclr,poizan42/coreclr,JosephTremoulet/coreclr,cmckinsey/coreclr,cshung/coreclr,ragmani/coreclr,krk/coreclr,hseok-oh/coreclr,rartemev/coreclr,rartemev/coreclr,jamesqo/coreclr,cmckinsey/coreclr,cydhaselton/coreclr,hseok-oh/coreclr,russellhadley/coreclr,wtgodbe/coreclr,yizhang82/coreclr,ruben-ayrapetyan/coreclr,qiudesong/coreclr,wateret/coreclr,kyulee1/coreclr,kyulee1/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,wateret/coreclr,mskvortsov/coreclr,krk/coreclr,cydhaselton/coreclr,hseok-oh/coreclr,tijoytom/coreclr,pgavlin/coreclr,sagood/coreclr,mmitche/coreclr,krk/coreclr,qiudesong/coreclr,sagood/coreclr,James-Ko/coreclr,cshung/coreclr,krk/coreclr,alexperovich/coreclr,alexperovich/coreclr