Remove pinned VRegs. (#108)

src/lib.rs

@@ -1117,23 +1117,6 @@ pub trait Function {
         &[]
     }
 
-    /// Is the given vreg pinned to a preg? If so, every use of the
-    /// vreg is automatically assigned to the preg, and live-ranges of
-    /// the vreg allocate the preg exclusively (are not spilled
-    /// elsewhere). The user must take care not to have too many live
-    /// pinned vregs such that allocation is no longer possible;
-    /// liverange computation will check that this is the case (that
-    /// there are enough remaining allocatable pregs of every class to
-    /// hold all Reg-constrained operands).
-    ///
-    /// Pinned vregs are implicitly live-in to the function: that is,
-    /// one can use a pinned vreg without having first defined it, and
-    /// this will take the value that that physical register (to which
-    /// the vreg is pinned) had at function entry.
-    fn is_pinned_vreg(&self, _: VReg) -> Option<PReg> {
-        None
-    }
-
     // --------------
     // Spills/reloads
     // --------------