cmd/compile: recognize OpS390XLoweredNilCheck as a nil check in the scheduler
cmd/compile: recognize OpS390XLoweredNilCheck as a nil check in the scheduler

Before this change a nil check on s390x could be scheduled after the
target pointer has been dereferenced.

Change-Id: I7ea40a4b52f975739f6db183a2794be4981c4e3d
Reviewed-on: https://go-review.googlesource.com/29730
Run-TryBot: Michael Munday <8f145917441a88646319703b14b4bef730f48765@ca.ibm.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

CAFxX/go,Cofyc/go,cloudflare/go,codestation/go,polyverse-security/go,akutz/go,Cofyc/go,momchil-velikov/go,josharian/go,vsekhar/elastic-go,polyverse-security/go,goodlang/good,momchil-velikov/go,momchil-velikov/go,josharian/go,linux-on-ibm-z/go,polyverse-security/go,akutz/go,Cofyc/go,suncycheng/go,CAFxX/go,josharian/go,derekmarcotte/go,nawawi/go,derekmarcotte/go,golang/go,nawawi/go,ImJasonH/go,nawawi/go,nawawi/go,momchil-velikov/go,akutz/go,ImJasonH/go,linux-on-ibm-z/go,josharian/go,goodlang/good,akutz/go,derekmarcotte/go,suncycheng/go,codestation/go,nawawi/go,ImJasonH/go,polyverse-security/go,suncycheng/go,Cofyc/go,suncycheng/go,CAFxX/go,polyverse-security/go,cloudflare/go,josharian/go,ImJasonH/go,polyverse-security/go,codestation/go,goodlang/good,polyverse-security/go,Cofyc/go,vsekhar/elastic-go,momchil-velikov/go,cloudflare/go,vsekhar/elastic-go,cloudflare/go,codestation/go,CAFxX/go,goodlang/good,vsekhar/elastic-go,linux-on-ibm-z/go,Cofyc/go,josharian/go,codestation/go,golang/go,goodlang/good,suncycheng/go,goodlang/good,momchil-velikov/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,codestation/go,polyverse-security/go,vsekhar/elastic-go,linux-on-ibm-z/go,nawawi/go,derekmarcotte/go,akutz/go,josharian/go,josharian/go,derekmarcotte/go,akutz/go,golang/go,ImJasonH/go,Cofyc/go,derekmarcotte/go,cloudflare/go,cloudflare/go,vsekhar/elastic-go,linux-on-ibm-z/go,suncycheng/go,goodlang/good,ImJasonH/go,christopher-henderson/Go,golang/go,suncycheng/go,derekmarcotte/go,momchil-velikov/go,codestation/go,nawawi/go,CAFxX/go,vsekhar/elastic-go,golang/go,momchil-velikov/go,akutz/go,cloudflare/go,vsekhar/elastic-go,ImJasonH/go,linux-on-ibm-z/go,golang/go,linux-on-ibm-z/go,goodlang/good,ImJasonH/go,linux-on-ibm-z/go,codestation/go,cloudflare/go,akutz/go,golang/go,CAFxX/go,derekmarcotte/go,suncycheng/go,Cofyc/go