ValueRecoveries speak of registers. The FTL doesn't speak of registers. Also, the FTL doesn't have to reason about the plethora of places that a value could have been put into; it just needs to know the LLVMValueRef (i.e. LValue). In fact, the FTL really just needs to speak in terms of values-with-formats - essentially a modestly type-refined LLVM value.
Created attachment 196209 [details] the patch
Comment on attachment 196209 [details] the patch r=me
Landed in http://trac.webkit.org/changeset/147487