This is in preparation for inverting the JSC stack. Currently a virtual register value of -1 is used as an invalid virtual register. When the stack is inverted, -1 will be a valid register. Some places in the code use a literal -1 while others use the enum InvalidVirtualRegister. All places should use the InvalidVirtualRegister enum and its value should be a reasonable "invalid" value.
Created attachment 211113 [details]
Committed r155420: <http://trac.webkit.org/changeset/155420>