Bump regalloc2 to 0.5.0 (#5345)

* Bump the regalloc2 dependency to 0.5.0
* Replace preg_set_from_machine_env with PRegSet::from
* Vet the regalloc2 update

cranelift/codegen/src/machinst/lower.rs

@@ -25,7 +25,7 @@ use regalloc2::{MachineEnv, PRegSet};
 use smallvec::{smallvec, SmallVec};
 use std::fmt::Debug;
 
-use super::{preg_set_from_machine_env, VCodeBuildDirection, VRegAllocator};
+use super::{VCodeBuildDirection, VRegAllocator};
 
 /// An "instruction color" partitions CLIF instructions by side-effecting ops.
 /// All instructions with the same "color" are guaranteed not to be separated by
@@ -417,7 +417,7 @@ impl<'func, I: VCodeInst> Lower<'func, I> {
         Ok(Lower {
             f,
             flags,
-            allocatable: preg_set_from_machine_env(machine_env),
+            allocatable: PRegSet::from(machine_env),
             vcode,
             vregs,
             value_regs,

cranelift/codegen/src/machinst/reg.rs

@@ -4,7 +4,7 @@
 
 use alloc::{string::String, vec::Vec};
 use core::{fmt::Debug, hash::Hash};
-use regalloc2::{Allocation, MachineEnv, Operand, OperandConstraint, PReg, PRegSet, VReg};
+use regalloc2::{Allocation, Operand, OperandConstraint, PReg, PRegSet, VReg};
 
 #[cfg(feature = "enable-serde")]
 use serde::{Deserialize, Serialize};
@@ -38,26 +38,6 @@ pub fn first_user_vreg_index() -> usize {
     PINNED_VREGS
 }
 
-/// Collect the registers from a regalloc2 MachineEnv into a PRegSet.
-/// TODO: remove this once it's upstreamed in regalloc2
-pub fn preg_set_from_machine_env(machine_env: &MachineEnv) -> PRegSet {
-    let mut regs = PRegSet::default();
-
-    for class in machine_env.preferred_regs_by_class.iter() {
-        for reg in class.iter() {
-            regs.add(*reg);
-        }
-    }
-
-    for class in machine_env.non_preferred_regs_by_class.iter() {
-        for reg in class.iter() {
-            regs.add(*reg);
-        }
-    }
-
-    regs
-}
-
 /// A register named in an instruction. This register can be either a
 /// virtual register or a fixed physical register. It does not have
 /// any constraints applied to it: those can be added later in