Remove PRegData::reg and use PReg::from_index instead

Performance impact is negligible but this is a good cleanup.

src/ion/data_structures.rs

@@ -264,7 +264,6 @@ pub struct VRegData {
 
 #[derive(Clone, Debug)]
 pub struct PRegData {
-    pub reg: PReg,
     pub allocations: LiveRangeSet,
     pub is_stack: bool,
 }

src/ion/liveranges.rs

@@ -102,17 +102,10 @@ impl<'a, F: Function> Env<'a, F> {
         self.pregs.resize(
             PReg::NUM_INDEX,
             PRegData {
-                reg: PReg::invalid(),
                 allocations: LiveRangeSet::new(),
                 is_stack: false,
             },
         );
-        for i in 0..=PReg::MAX {
-            let preg_int = PReg::new(i, RegClass::Int);
-            self.pregs[preg_int.index()].reg = preg_int;
-            let preg_float = PReg::new(i, RegClass::Float);
-            self.pregs[preg_float.index()].reg = preg_float;
-        }
         for &preg in &self.env.fixed_stack_slots {
             self.pregs[preg.index()].is_stack = true;
         }

src/ion/moves.rs

@@ -20,7 +20,7 @@ use super::{
 use crate::moves::ParallelMoves;
 use crate::{
     Allocation, Block, Edit, Function, Inst, InstPosition, OperandConstraint, OperandKind,
-    OperandPos, ProgPoint, RegClass, VReg,
+    OperandPos, PReg, ProgPoint, RegClass, VReg,
 };
 use smallvec::{smallvec, SmallVec};
 use std::fmt::Debug;
@@ -697,7 +697,7 @@ impl<'a, F: Function> Env<'a, F> {
         // Handle multi-fixed-reg constraints by copying.
         for fixup in std::mem::replace(&mut self.multi_fixed_reg_fixups, vec![]) {
             let from_alloc = self.get_alloc(fixup.pos.inst(), fixup.from_slot as usize);
-            let to_alloc = Allocation::reg(self.pregs[fixup.to_preg.index()].reg);
+            let to_alloc = Allocation::reg(PReg::from_index(fixup.to_preg.index()));
             log::trace!(
                 "multi-fixed-move constraint at {:?} from {} to {} for v{}",
                 fixup.pos,
@@ -715,7 +715,7 @@ impl<'a, F: Function> Env<'a, F> {
             self.set_alloc(
                 fixup.pos.inst(),
                 fixup.to_slot as usize,
-                Allocation::reg(self.pregs[fixup.to_preg.index()].reg),
+                Allocation::reg(PReg::from_index(fixup.to_preg.index())),
             );
         }
 

src/ion/process.rs

@@ -197,7 +197,7 @@ impl<'a, F: Function> Env<'a, F> {
         }
 
         // We can allocate! Add our ranges to the preg's BTree.
-        let preg = self.pregs[reg.index()].reg;
+        let preg = PReg::from_index(reg.index());
         log::trace!("  -> bundle {:?} assigned to preg {:?}", bundle, preg);
         self.bundles[bundle.index()].allocation = Allocation::reg(preg);
         for entry in &self.bundles[bundle.index()].ranges {