[dev.ssa] cmd/compile: handle OpCopy loops in rewrite
[dev.ssa] cmd/compile: handle OpCopy loops in rewrite

Change-Id: Icbaad6e5cbfc5430a651538fe90c0a9ee664faf4
Reviewed-on: https://go-review.googlesource.com/12360
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

akutz/go,binarycrusader/go,codestation/go,mwhudson/go,binarycrusader/go,Samurais/go,suncycheng/go,Samurais/go,linux-on-ibm-z/go,theif519/go,Samurais/go,nawawi/go,cloudflare/go,josharian/go,akutz/go,momchil-velikov/go,golang/go,codestation/go,mwhudson/go,4ad/go,josharian/go,nawawi/go,codestation/go,derekmarcotte/go,vsekhar/elastic-go,ImJasonH/go,polyverse-security/go,vanloswang/go,Cofyc/go,vsekhar/elastic-go,binarycrusader/go,linux-on-ibm-z/go,codestation/go,vanloswang/go,ImJasonH/go,akutz/go,miolini/go,miolini/go,golang/go,derekmarcotte/go,josharian/go,cloudflare/go,akutz/go,golang/go,akutz/go,goodlang/good,mwhudson/go,christopher-henderson/Go,binarycrusader/go,cyberroadie/go,miolini/go,cloudflare/go,vsekhar/elastic-go,golang/go,4ad/go,Samurais/go,suncycheng/go,ganboing/go-esx,Cofyc/go,suncycheng/go,goodlang/good,CAFxX/go,nawawi/go,CAFxX/go,ganboing/go-esx,momchil-velikov/go,derekmarcotte/go,miolini/go,cyberroadie/go,linux-on-ibm-z/go,derekmarcotte/go,ImJasonH/go,codestation/go,Cofyc/go,golang/go,CAFxX/go,4ad/go,polyverse-security/go,ImJasonH/go,josharian/go,Samurais/go,linux-on-ibm-z/go,goodlang/good,vanloswang/go,linux-on-ibm-z/go,miolini/go,ganboing/go-esx,josharian/go,momchil-velikov/go,golang/go,Cofyc/go,polyverse-security/go,polyverse-security/go,codestation/go,momchil-velikov/go,derekmarcotte/go,derekmarcotte/go,mwhudson/go,4ad/go,cloudflare/go,codestation/go,cyberroadie/go,codestation/go,josharian/go,akutz/go,cyberroadie/go,nawawi/go,ganboing/go-esx,nawawi/go,Samurais/go,cyberroadie/go,linux-on-ibm-z/go,binarycrusader/go,miolini/go,goodlang/good,CAFxX/go,cloudflare/go,momchil-velikov/go,cloudflare/go,4ad/go,cyberroadie/go,vsekhar/elastic-go,Cofyc/go,CAFxX/go,mwhudson/go,Samurais/go,vanloswang/go,mwhudson/go,vanloswang/go,mwhudson/go,binarycrusader/go,ImJasonH/go,ganboing/go-esx,vanloswang/go,goodlang/good,suncycheng/go,vanloswang/go,vsekhar/elastic-go,Cofyc/go,momchil-velikov/go,vsekhar/elastic-go,golang/go,theif519/go,cyberroadie/go,vsekhar/elastic-go,4ad/go,theif519/go,miolini/go,momchil-velikov/go,polyverse-security/go,suncycheng/go,derekmarcotte/go,Cofyc/go,suncycheng/go,theif519/go,akutz/go,cyberroadie/go,polyverse-security/go,nawawi/go,4ad/go,nawawi/go,binarycrusader/go,polyverse-security/go,binarycrusader/go,linux-on-ibm-z/go,4ad/go,theif519/go,cloudflare/go,miolini/go,goodlang/good,ImJasonH/go,cloudflare/go,CAFxX/go,josharian/go,akutz/go,goodlang/good,suncycheng/go,ImJasonH/go,nawawi/go,vsekhar/elastic-go,ImJasonH/go,linux-on-ibm-z/go,Samurais/go,Cofyc/go,theif519/go,momchil-velikov/go,mwhudson/go,suncycheng/go,golang/go,ganboing/go-esx,vanloswang/go,CAFxX/go,derekmarcotte/go,ganboing/go-esx,ganboing/go-esx,theif519/go,polyverse-security/go,goodlang/good,josharian/go,CAFxX/go,theif519/go