init

.vscode/settings.json

@@ -0,0 +1,9 @@
+{
+    "editor.formatOnSave": true,
+    "[rust]": {
+        "editor.defaultFormatter": "rust-lang.rust-analyzer"
+    },
+    "rust-analyzer.cargo.features": [
+        "default"
+    ]
+}

src/cfg.rs

@@ -33,7 +33,7 @@ pub struct CFGInfo {
 }
 
 impl CFGInfo {
-    pub fn new<F: Function>(f: &F) -> Result<CFGInfo, RegAllocError> {
+    pub fn new<F: Function>(f: &F, needs_loop_depth: bool) -> Result<CFGInfo, RegAllocError> {
         let postorder = postorder::calculate(f.num_blocks(), f.entry_block(), |block| {
             f.block_succs(block)
         });
@@ -98,22 +98,24 @@ impl CFGInfo {
         }
 
         let mut approx_loop_depth = vec![];
-        let mut backedge_stack: SmallVec<[usize; 4]> = smallvec![];
-        let mut cur_depth = 0;
-        for block in 0..f.num_blocks() {
-            if backedge_in[block] > 0 {
-                cur_depth += 1;
-                backedge_stack.push(backedge_in[block]);
-            }
+        if needs_loop_depth {
+            let mut backedge_stack: SmallVec<[usize; 4]> = smallvec![];
+            let mut cur_depth = 0;
+            for block in 0..f.num_blocks() {
+                if backedge_in[block] > 0 {
+                    cur_depth += 1;
+                    backedge_stack.push(backedge_in[block]);
+                }
 
-            approx_loop_depth.push(cur_depth);
+                approx_loop_depth.push(cur_depth);
 
-            while backedge_stack.len() > 0 && backedge_out[block] > 0 {
-                backedge_out[block] -= 1;
-                *backedge_stack.last_mut().unwrap() -= 1;
-                if *backedge_stack.last().unwrap() == 0 {
-                    cur_depth -= 1;
-                    backedge_stack.pop();
+                while backedge_stack.len() > 0 && backedge_out[block] > 0 {
+                    backedge_out[block] -= 1;
+                    *backedge_stack.last_mut().unwrap() -= 1;
+                    if *backedge_stack.last().unwrap() == 0 {
+                        cur_depth -= 1;
+                        backedge_stack.pop();
+                    }
                 }
             }
         }

src/ion/fast_alloc.rs

@@ -0,0 +1,311 @@
+use alloc::vec;
+use alloc::vec::Vec;
+use smallvec::{smallvec, SmallVec};
+use std::convert::TryFrom;
+
+use crate::{
+    cfg::CFGInfo, Allocation, Block, Edit, Function, Inst, MachineEnv, Operand, OperandConstraint,
+    OperandKind, OperandPos, Output, PReg, ProgPoint, RegAllocError, RegClass, SpillSlot, VReg,
+};
+
+#[derive(Default, Clone, Copy)]
+struct VRegData {
+    pub preg: Option<PReg>,
+    pub slot_idx: Option<u32>,
+    pub reftype: bool,
+}
+
+#[derive(Default, Clone, Copy)]
+struct PRegData {
+    pub vreg: Option<u32>,
+    pub stack_pseudo: bool,
+}
+
+#[derive(Default, Clone, Copy)]
+struct BlockData {
+    pub allocated: bool,
+}
+
+struct FastAllocState<'a, F: Function> {
+    pub vregs: Vec<VRegData>,
+    pub pregs: Vec<PRegData>,
+    pub blocks: Vec<BlockData>,
+
+    pub preorder: Vec<Block>,
+    pub reg_order_int: Vec<PReg>,
+    pub reg_order_float: Vec<PReg>,
+
+    pub cur_stack_slot_idx: u32,
+    pub reftype_vregs_in_pregs_count: u32,
+
+    pub stack_slot_count_int: u8,
+    pub stack_slot_count_float: u8,
+
+    pub allocs: Vec<Allocation>,
+    pub inst_alloc_offsets: Vec<u32>,
+    pub edits: Vec<(ProgPoint, Edit)>,
+    pub safepoint_slots: Vec<(ProgPoint, Allocation)>,
+
+    pub func: &'a F,
+    pub mach_env: &'a MachineEnv,
+    pub cfg: &'a CFGInfo,
+}
+
+impl<'a, F: Function> FastAllocState<'a, F> {
+    pub fn init(func: &'a F, mach_env: &'a MachineEnv, cfg: &'a CFGInfo) -> Self {
+        let vregs = {
+            let mut vregs = Vec::with_capacity(func.num_vregs());
+            vregs.resize(func.num_vregs(), VRegData::default());
+
+            for vreg in func.reftype_vregs() {
+                vregs[vreg.vreg()].reftype = true;
+            }
+
+            vregs
+        };
+
+        let pregs = {
+            let mut pregs = Vec::with_capacity(PReg::NUM_INDEX);
+            pregs.resize(PReg::NUM_INDEX, PRegData::default());
+
+            for preg in &mach_env.fixed_stack_slots {
+                pregs[preg.index()].stack_pseudo = true;
+            }
+            pregs
+        };
+
+        let blocks = {
+            let mut blocks = Vec::with_capacity(func.num_blocks());
+            blocks.resize(func.num_blocks(), BlockData::default());
+            blocks
+        };
+
+        let reg_order_int = {
+            let class = RegClass::Int as usize;
+            let amount = mach_env.preferred_regs_by_class[class].len()
+                + mach_env.non_preferred_regs_by_class[class].len();
+            let mut reg_order = Vec::with_capacity(amount);
+            reg_order.extend_from_slice(&mach_env.preferred_regs_by_class[class]);
+            reg_order.extend_from_slice(&mach_env.non_preferred_regs_by_class[class]);
+            reg_order
+        };
+
+        let reg_order_float = {
+            let class = RegClass::Float as usize;
+            let amount = mach_env.preferred_regs_by_class[class].len()
+                + mach_env.non_preferred_regs_by_class[class].len();
+            let mut reg_order = Vec::with_capacity(amount);
+            reg_order.extend_from_slice(&mach_env.preferred_regs_by_class[class]);
+            reg_order.extend_from_slice(&mach_env.non_preferred_regs_by_class[class]);
+            reg_order
+        };
+
+        let mut inst_alloc_offsets = Vec::with_capacity(func.num_insts());
+        inst_alloc_offsets.resize(func.num_insts(), 0);
+
+        Self {
+            vregs,
+            pregs,
+            blocks,
+
+            preorder: Self::calc_preorder(func),
+            reg_order_int,
+            reg_order_float,
+
+            cur_stack_slot_idx: 0,
+            reftype_vregs_in_pregs_count: 0,
+
+            stack_slot_count_int: u8::try_from(func.spillslot_size(RegClass::Int))
+                .expect("that's a big integer"),
+            stack_slot_count_float: u8::try_from(func.spillslot_size(RegClass::Float))
+                .expect("that's a big float"),
+
+            allocs: Vec::new(),
+            inst_alloc_offsets,
+            edits: Vec::new(),
+            safepoint_slots: Vec::new(),
+
+            func,
+            mach_env,
+            cfg,
+        }
+    }
+
+    pub fn get_or_alloc_stack_slot(&mut self, vreg: VReg) -> u32 {
+        if let Some(idx) = self.vregs[vreg.vreg()].slot_idx {
+            return idx;
+        }
+
+        self.alloc_stack_slot(vreg)
+    }
+
+    pub fn alloc_stack_slot(&mut self, vreg: VReg) -> u32 {
+        let data = &mut self.vregs[vreg.vreg()];
+        if data.slot_idx.is_some() {
+            panic!("Trying to allocate already allocated stack slot");
+        }
+
+        let size = if vreg.class() == RegClass::Int {
+            self.stack_slot_count_int
+        } else {
+            self.stack_slot_count_float
+        };
+        let idx = self.cur_stack_slot_idx;
+        self.cur_stack_slot_idx += size as u32;
+        data.slot_idx = Some(idx);
+        idx
+    }
+
+    pub fn move_to_preg(&mut self, vreg: VReg, preg: PReg, pos: ProgPoint) {
+        if let Some(vreg) = &self.pregs[preg.index()].vreg {
+            let vdata = &mut self.vregs[*vreg as usize];
+            debug_assert!(vdata.preg.is_some());
+            debug_assert_eq!(vdata.preg.unwrap(), preg);
+            vdata.preg = None;
+        }
+
+        if let Some(preg) = &self.vregs[vreg.vreg()].preg {
+            // TODO: allow multiple pregs for a single vreg?
+            let pdata = &mut self.pregs[preg.index()];
+            debug_assert!(pdata.vreg.is_some());
+            debug_assert_eq!(pdata.vreg.unwrap(), vreg.vreg() as u32);
+            pdata.vreg = None;
+        }
+
+        let vdata = &mut self.vregs[vreg.vreg()];
+        let pdata = &mut self.pregs[preg.index()];
+
+        if vdata.slot_idx.is_none() {
+            panic!("Trying to move from vreg that has no stack slot to preg");
+        }
+
+        self.edits.push((
+            pos,
+            Edit::Move {
+                from: Allocation::stack(SpillSlot::new(vdata.slot_idx.unwrap() as usize)),
+                to: Allocation::reg(preg),
+            },
+        ));
+        vdata.preg = Some(preg);
+        pdata.vreg = Some(vreg.vreg() as u32);
+
+        if vdata.reftype {
+            self.reftype_vregs_in_pregs_count += 1;
+        }
+    }
+
+    pub fn move_to_stack(&mut self, preg: PReg, vreg: VReg, pos: ProgPoint) {
+        let vdata = &mut self.vregs[vreg.vreg()];
+        let pdata = &mut self.pregs[preg.index()];
+        if pdata.vreg.is_none() || vdata.preg.is_none() {
+            panic!("Trying to move from unallocated preg/vreg to stack");
+        }
+        debug_assert_eq!(vdata.preg.unwrap(), preg);
+        debug_assert_eq!(pdata.vreg.unwrap(), vreg.vreg() as u32);
+
+        if vdata.slot_idx.is_none() {
+            panic!("Trying to move to vreg without stack slot");
+        }
+
+        self.edits.push((
+            pos,
+            Edit::Move {
+                from: Allocation::reg(preg),
+                to: Allocation::stack(SpillSlot::new(vdata.slot_idx.unwrap() as usize)),
+            },
+        ));
+    }
+
+    pub fn clear_preg(&mut self, preg: PReg) {
+        let pdata = &mut self.pregs[preg.index()];
+        if let Some(vreg) = pdata.vreg {
+            let vdata = &mut self.vregs[vreg as usize];
+            debug_assert_eq!(vdata.preg.unwrap(), preg);
+            vdata.preg = None;
+            pdata.vreg = None;
+            if vdata.reftype {
+                self.reftype_vregs_in_pregs_count -= 1;
+            }
+        }
+    }
+
+    pub fn clear_vreg_from_reg(&mut self, vreg: VReg) {
+        let vdata = &mut self.vregs[vreg.vreg()];
+        if let Some(preg) = vdata.preg {
+            debug_assert_eq!(self.pregs[preg.index()].vreg.unwrap(), vreg.vreg() as u32);
+            self.pregs[preg.index()].vreg = None;
+            vdata.preg = None;
+
+            if vdata.reftype {
+                self.reftype_vregs_in_pregs_count -= 1;
+            }
+        }
+    }
+
+    fn calc_preorder(func: &F) -> Vec<Block> {
+        let entry = func.entry_block();
+        let mut ret = vec![entry];
+
+        struct State<'a> {
+            block: Block,
+            succs: &'a [Block],
+            next_succ: usize,
+        }
+        let mut stack: SmallVec<[State; 64]> = smallvec![];
+
+        stack.push(State {
+            block: entry,
+            succs: func.block_succs(entry),
+            next_succ: 0,
+        });
+
+        while let Some(ref mut state) = stack.last_mut() {
+            if state.next_succ >= state.succs.len() {
+                stack.pop();
+                continue;
+            }
+
+            let block = state.succs[state.next_succ];
+            let succs = func.block_succs(block);
+            ret.push(block);
+
+            state.next_succ += 1;
+            if state.next_succ >= state.succs.len() {
+                stack.pop();
+            }
+
+            if !succs.is_empty() {
+                stack.push(State {
+                    block,
+                    succs: func.block_succs(block),
+                    next_succ: 0,
+                });
+            }
+        }
+
+        ret
+    }
+}
+
+pub fn run<F: Function>(
+    func: &F,
+    mach_env: &MachineEnv,
+    cfg: CFGInfo,
+) -> Result<Output, RegAllocError> {
+    if func.multi_spillslot_named_by_last_slot() {
+        panic!("MultiSpillslotIndexPos not supported");
+    }
+
+    let mut state = FastAllocState::init(func, mach_env, &cfg);
+
+    todo!("")
+}
+
+fn setup_entry_params<'a, F: Function>(
+    state: &mut FastAllocState<'a, F>,
+) -> Result<(), RegAllocError> {
+    // we need to set the vreg location for the initial block parameters and copy them to the stack
+    let entry = state.func.entry_block();
+
+    todo!("")
+}

src/ion/fast_alloc.rs.bak

@@ -0,0 +1,594 @@
+use alloc::vec;
+use alloc::vec::Vec;
+use smallvec::{smallvec, SmallVec};
+
+use crate::{
+    cfg::CFGInfo, Allocation, Block, Edit, Function, Inst, MachineEnv, Operand, OperandConstraint,
+    OperandKind, OperandPos, Output, PReg, ProgPoint, RegAllocError, RegClass, SpillSlot, VReg,
+};
+
+#[derive(Clone, Copy)]
+struct VRegInfo {
+    pub stack_slot: Option<u32>,
+    pub alloc_at_inst: Inst,
+    pub cur_reg: Option<PReg>,
+}
+
+impl Default for VRegInfo {
+    fn default() -> Self {
+        Self {
+            stack_slot: None,
+            alloc_at_inst: Inst::invalid(),
+            cur_reg: None,
+        }
+    }
+}
+
+struct AllocState {
+    pub vregs: Vec<VRegInfo>,
+    pub preorder: Vec<Block>,
+    pub allocs: Vec<Allocation>,
+    pub inst_alloc_offsets: Vec<u32>,
+    pub edits: Vec<(ProgPoint, Edit)>,
+    pub cur_stack_slot_idx: u32,
+    pub safepoint_slots: Vec<(ProgPoint, Allocation)>,
+}
+
+impl AllocState {
+    pub fn init<F: Function>(func: &F) -> Self {
+        let mut vregs = Vec::with_capacity(func.num_vregs());
+        vregs.resize(func.num_vregs(), VRegInfo::default());
+
+        let mut inst_alloc_offsets = Vec::with_capacity(func.num_insts());
+        inst_alloc_offsets.resize(func.num_insts(), 0);
+
+        Self {
+            vregs,
+            preorder: Self::calc_preorder(func),
+            allocs: Vec::new(),
+            inst_alloc_offsets,
+            edits: Vec::new(),
+            cur_stack_slot_idx: 0,
+            safepoint_slots: Vec::new(),
+        }
+    }
+
+    fn calc_preorder<F: Function>(func: &F) -> Vec<Block> {
+        let entry = func.entry_block();
+        let mut ret = vec![entry];
+
+        struct State<'a> {
+            block: Block,
+            succs: &'a [Block],
+            next_succ: usize,
+        }
+        let mut stack: SmallVec<[State; 64]> = smallvec![];
+
+        stack.push(State {
+            block: entry,
+            succs: func.block_succs(entry),
+            next_succ: 0,
+        });
+
+        while let Some(ref mut state) = stack.last_mut() {
+            if state.next_succ >= state.succs.len() {
+                stack.pop();
+                continue;
+            }
+
+            let block = state.succs[state.next_succ];
+            let succs = func.block_succs(block);
+            ret.push(block);
+
+            state.next_succ += 1;
+            if state.next_succ >= state.succs.len() {
+                stack.pop();
+            }
+
+            if !succs.is_empty() {
+                stack.push(State {
+                    block,
+                    succs: func.block_succs(block),
+                    next_succ: 0,
+                });
+            }
+        }
+
+        ret
+    }
+}
+
+pub fn run<F: Function>(
+    func: &F,
+    mach_env: &MachineEnv,
+    cfg: CFGInfo,
+) -> Result<Output, RegAllocError> {
+    let mut state = AllocState::init(func);
+
+    let reg_order_int = {
+        let class = RegClass::Int as usize;
+        let amount = mach_env.preferred_regs_by_class[class].len()
+            + mach_env.non_preferred_regs_by_class[class].len();
+        let mut reg_order = Vec::with_capacity(amount);
+        reg_order.extend_from_slice(&mach_env.preferred_regs_by_class[class]);
+        reg_order.extend_from_slice(&mach_env.non_preferred_regs_by_class[class]);
+        reg_order
+    };
+
+    let reg_order_float = {
+        let class = RegClass::Float as usize;
+        let amount = mach_env.preferred_regs_by_class[class].len()
+            + mach_env.non_preferred_regs_by_class[class].len();
+        let mut reg_order = Vec::with_capacity(amount);
+        reg_order.extend_from_slice(&mach_env.preferred_regs_by_class[class]);
+        reg_order.extend_from_slice(&mach_env.non_preferred_regs_by_class[class]);
+        reg_order
+    };
+
+    let slot_size_int = func.spillslot_size(RegClass::Int) as u32;
+    let slot_size_float = func.spillslot_size(RegClass::Float) as u32;
+
+    // TODO: this currently does not handle multiple defs/uses of the same vreg properly
+
+    // TODO: move to AllocState, needs to also contain if this is a pseudo-preg and refers to the stack
+    let mut preg_state: Vec<VReg> = Vec::with_capacity(PReg::NUM_INDEX);
+    preg_state.resize(PReg::NUM_INDEX, VReg::invalid());
+
+    for block in &state.preorder {
+        for inst in func.block_insns(*block).iter() {
+            let operands = func.inst_operands(inst);
+            let alloc_idx = state.allocs.len();
+            state.inst_alloc_offsets[inst.index()] = alloc_idx as u32;
+
+            state
+                .allocs
+                .resize(alloc_idx + operands.len(), Allocation::none());
+
+            // both of these smallvecs could hold 16 entries
+            // late uses may not be chosen as a target for writes
+            let mut late_use_regs: SmallVec<[PReg; 4]> = smallvec![];
+            let mut early_write_regs: SmallVec<[PReg; 4]> = smallvec![];
+
+            // TODO: wouldnt need this if we look up the inst a vreg was allocated at
+            let mut regs_allocated: SmallVec<[PReg; 8]> = smallvec![];
+
+            let mut cur_idx_int = 0;
+            let mut cur_idx_float = 0;
+            let mut has_early_write = false;
+
+            // allocate uses; fixed reg first, then the others
+            for (i, op) in operands.iter().enumerate() {
+                if op.kind() != OperandKind::Use {
+                    if op.pos() != OperandPos::Early {
+                        continue;
+                    }
+                    has_early_write = true;
+                }
+
+                let vreg = op.vreg();
+
+                match op.constraint() {
+                    OperandConstraint::Any | OperandConstraint::Reg | OperandConstraint::Stack => {
+                        continue
+                    }
+                    OperandConstraint::FixedReg(reg) => {
+                        if preg_state[reg.index()] != VReg::invalid()
+                            && preg_state[reg.index()] != vreg
+                        {
+                            return Err(RegAllocError::TooManyLiveRegs);
+                        }
+
+                        state.allocs[alloc_idx + i] = Allocation::reg(reg);
+                        preg_state[reg.index()] = vreg;
+                        state.vregs[vreg.vreg()].alloc_at_inst = inst;
+                        state.vregs[vreg.vreg()].cur_reg = Some(reg);
+                        regs_allocated.push(reg);
+                        if op.pos() == OperandPos::Late {
+                            late_use_regs.push(reg);
+                        }
+
+                        if op.kind() == OperandKind::Use {
+                            // Early Defs do not need to be moved
+                            match state.vregs[vreg.vreg()].stack_slot {
+                                Some(slot) => {
+                                    state.edits.push((
+                                        ProgPoint::before(inst),
+                                        Edit::Move {
+                                            from: Allocation::stack(SpillSlot::new(slot as usize)),
+                                            to: Allocation::reg(reg),
+                                        },
+                                    ));
+                                }
+                                None => {
+                                    return Err(RegAllocError::SSA(vreg, inst));
+                                }
+                            }
+                        } else {
+                            early_write_regs.push(reg);
+                            let slot = match state.vregs[vreg.vreg()].stack_slot {
+                                Some(slot) => slot,
+                                None => {
+                                    let size = if op.class() == RegClass::Int {
+                                        slot_size_int
+                                    } else {
+                                        slot_size_float
+                                    };
+                                    let slot = state.cur_stack_slot_idx;
+                                    state.cur_stack_slot_idx += size;
+                                    state.vregs[vreg.vreg()].stack_slot = Some(slot);
+                                    slot
+                                }
+                            };
+                            state.edits.push((
+                                ProgPoint::after(inst),
+                                Edit::Move {
+                                    from: Allocation::reg(reg),
+                                    to: Allocation::stack(SpillSlot::new(slot as usize)),
+                                },
+                            ));
+                        }
+                    }
+                    OperandConstraint::Reuse(_) => panic!("Reuse constraint for Use/Early-Write"),
+                }
+            }
+
+            for (i, op) in operands.iter().enumerate() {
+                if op.kind() != OperandKind::Use {
+                    if op.pos() != OperandPos::Early {
+                        continue;
+                    }
+                    continue;
+                }
+
+                let vreg = op.vreg();
+                let vreg_idx = vreg.vreg();
+
+                match op.constraint() {
+                    OperandConstraint::Stack => {
+                        // values need to be on stack already
+                        match state.vregs[vreg_idx].stack_slot {
+                            Some(slot) => {
+                                state.allocs[alloc_idx + i] =
+                                    Allocation::stack(SpillSlot::new(slot as usize));
+                            }
+                            None => {
+                                if op.kind() == OperandKind::Use {
+                                    return Err(RegAllocError::SSA(vreg, inst));
+                                }
+                                // alloc stack slot
+                                let size = if op.class() == RegClass::Int {
+                                    slot_size_int
+                                } else {
+                                    slot_size_float
+                                };
+                                let slot = state.cur_stack_slot_idx;
+                                state.cur_stack_slot_idx += size;
+                                state.allocs[alloc_idx + i] =
+                                    Allocation::stack(SpillSlot::new(slot as usize));
+                                state.vregs[vreg_idx].stack_slot = Some(slot);
+                            }
+                        }
+                    }
+                    // TODO: do any on stack?
+                    OperandConstraint::Any | OperandConstraint::Reg => {
+                        // check if vreg has been allocated before
+                        let mut alloc = None;
+                        for (j, op) in operands.iter().enumerate() {
+                            if j >= i {
+                                break;
+                            }
+
+                            if op.vreg() == vreg {
+                                alloc = Some(state.allocs[alloc_idx + j].clone());
+                                break;
+                            }
+                        }
+
+                        if let Some(a) = alloc {
+                            state.allocs[alloc_idx + i] = a;
+                            continue;
+                        }
+
+                        // find first non-allocated register
+                        let reg_order = if op.class() == RegClass::Int {
+                            &reg_order_int
+                        } else {
+                            &reg_order_float
+                        };
+                        let reg_order_idx = if op.class() == RegClass::Int {
+                            &mut cur_idx_int
+                        } else {
+                            &mut cur_idx_float
+                        };
+                        loop {
+                            if *reg_order_idx >= reg_order.len() {
+                                break;
+                            }
+
+                            if preg_state[reg_order[*reg_order_idx].index()] != VReg::invalid() {
+                                *reg_order_idx += 1;
+                                continue;
+                            }
+
+                            let reg = reg_order[*reg_order_idx];
+
+                            // TODO: helper func for alloc
+                            state.allocs[alloc_idx + i] = Allocation::reg(reg);
+                            preg_state[reg.index()] = vreg;
+                            state.vregs[vreg.vreg()].alloc_at_inst = inst;
+                            state.vregs[vreg.vreg()].cur_reg = Some(reg);
+                            regs_allocated.push(reg);
+                            if op.pos() == OperandPos::Late {
+                                late_use_regs.push(reg);
+                            }
+
+                            if op.kind() == OperandKind::Use {
+                                match state.vregs[vreg_idx].stack_slot {
+                                    Some(slot) => {
+                                        state.edits.push((
+                                            ProgPoint::before(inst),
+                                            Edit::Move {
+                                                from: Allocation::stack(SpillSlot::new(
+                                                    slot as usize,
+                                                )),
+                                                to: Allocation::reg(reg),
+                                            },
+                                        ));
+                                    }
+                                    None => {
+                                        return Err(RegAllocError::SSA(vreg, inst));
+                                    }
+                                }
+                            } else {
+                                early_write_regs.push(reg);
+                                let slot = match state.vregs[vreg.vreg()].stack_slot {
+                                    Some(slot) => slot,
+                                    None => {
+                                        let size = if op.class() == RegClass::Int {
+                                            slot_size_int
+                                        } else {
+                                            slot_size_float
+                                        };
+                                        let slot = state.cur_stack_slot_idx;
+                                        state.cur_stack_slot_idx += size;
+                                        state.vregs[vreg.vreg()].stack_slot = Some(slot);
+                                        slot
+                                    }
+                                };
+                                state.edits.push((
+                                    ProgPoint::after(inst),
+                                    Edit::Move {
+                                        from: Allocation::reg(reg),
+                                        to: Allocation::stack(SpillSlot::new(slot as usize)),
+                                    },
+                                ));
+                            }
+                        }
+
+                        // No register available
+                        // TODO: try to evict vreg that does not need to be in a preg
+                        if op.constraint() == OperandConstraint::Reg {
+                            return Err(RegAllocError::TooManyLiveRegs);
+                        }
+
+                        // any can live on the stack
+                        match state.vregs[vreg_idx].stack_slot {
+                            Some(slot) => {
+                                state.allocs[alloc_idx + i] =
+                                    Allocation::stack(SpillSlot::new(slot as usize));
+                            }
+                            None => {
+                                if op.kind() == OperandKind::Use {
+                                    return Err(RegAllocError::SSA(vreg, inst));
+                                }
+                                // alloc stack slot
+                                let size = if op.class() == RegClass::Int {
+                                    slot_size_int
+                                } else {
+                                    slot_size_float
+                                };
+                                let slot = state.cur_stack_slot_idx;
+                                state.cur_stack_slot_idx += size;
+                                state.allocs[alloc_idx + i] =
+                                    Allocation::stack(SpillSlot::new(slot as usize));
+                                state.vregs[vreg_idx].stack_slot = Some(slot);
+                            }
+                        }
+                    }
+                    OperandConstraint::FixedReg(_) => continue,
+                    OperandConstraint::Reuse(_) => unreachable!(),
+                }
+            }
+
+            // Handle writes
+            for (i, op) in operands.iter().enumerate() {
+                if op.kind() != OperandKind::Def || op.pos() == OperandPos::Early {
+                    continue;
+                }
+
+                let vreg = op.vreg();
+                let vreg_idx = vreg.vreg();
+
+                match op.constraint() {
+                    OperandConstraint::FixedReg(reg) => {
+                        let reg_idx = reg.index();
+
+                        if preg_state[reg_idx] != VReg::invalid() {
+                            // if the register is occupied by a late use we abort
+                            // TODO: move the allocation, if possible
+                            if late_use_regs.contains(&reg) || early_write_regs.contains(&reg) {
+                                todo!("trying to allocate fixed reg def on late use/early write");
+                            }
+
+                            // overwrite
+                            let vreg = preg_state[reg_idx].vreg();
+                            state.vregs[vreg].cur_reg = None;
+                        }
+
+                        preg_state[reg_idx] = vreg;
+                        state.vregs[vreg_idx].cur_reg = Some(reg);
+                        state.allocs[alloc_idx + i] = Allocation::reg(reg);
+
+                        match state.vregs[vreg_idx].stack_slot {
+                            None => {
+                                // alloc stack slot
+                                let size = if op.class() == RegClass::Int {
+                                    slot_size_int
+                                } else {
+                                    slot_size_float
+                                };
+                                let slot = state.cur_stack_slot_idx;
+                                state.cur_stack_slot_idx += size;
+                                state.vregs[vreg_idx].stack_slot = Some(slot);
+
+                                // move to stack after inst
+                                state.edits.push((
+                                    ProgPoint::after(inst),
+                                    Edit::Move {
+                                        from: Allocation::reg(reg),
+                                        to: Allocation::stack(SpillSlot::new(slot as usize)),
+                                    },
+                                ));
+                            }
+                            Some(_) => {
+                                return Err(RegAllocError::SSA(vreg, inst));
+                            }
+                        }
+                    }
+                    _ => continue,
+                }
+            }
+
+            cur_idx_int = 0;
+            cur_idx_float = 0;
+            for (i, op) in operands.iter().enumerate() {
+                if op.kind() != OperandKind::Def || op.pos() == OperandPos::Early {
+                    continue;
+                }
+
+                let vreg = op.vreg();
+                let vreg_idx = vreg.vreg();
+
+                match op.constraint() {
+                    OperandConstraint::Reg => {
+                        // find first non-allocated register
+                        let reg_order = if op.class() == RegClass::Int {
+                            &reg_order_int
+                        } else {
+                            &reg_order_float
+                        };
+                        let reg_order_idx = if op.class() == RegClass::Int {
+                            &mut cur_idx_int
+                        } else {
+                            &mut cur_idx_float
+                        };
+                        loop {
+                            if *reg_order_idx >= reg_order.len() {
+                                break;
+                            }
+                            let reg = reg_order[*reg_order_idx];
+
+                            if late_use_regs.contains(&reg) || early_write_regs.contains(&reg) {
+                                *reg_order_idx += 1;
+                                continue;
+                            }
+
+                            // remove allocated
+                            if preg_state[reg.index()] != VReg::invalid() {
+                                let vreg_idx = preg_state[reg.index()].vreg();
+                                state.vregs[vreg_idx].cur_reg = None;
+                            } else {
+                                regs_allocated.push(reg);
+                            }
+
+                            // TODO: helper func for alloc
+                            state.allocs[alloc_idx + i] = Allocation::reg(reg);
+                            preg_state[reg.index()] = vreg;
+                            state.vregs[vreg.vreg()].alloc_at_inst = inst;
+                            state.vregs[vreg.vreg()].cur_reg = Some(reg);
+
+                            // alloc stack slot
+                            let size = if op.class() == RegClass::Int {
+                                slot_size_int
+                            } else {
+                                slot_size_float
+                            };
+                            let slot = state.cur_stack_slot_idx;
+                            state.cur_stack_slot_idx += size;
+                            state.vregs[vreg_idx].stack_slot = Some(slot);
+
+                            match state.vregs[vreg_idx].stack_slot {
+                                Some(slot) => {
+                                    state.edits.push((
+                                        ProgPoint::after(inst),
+                                        Edit::Move {
+                                            from: Allocation::reg(reg),
+                                            to: Allocation::stack(SpillSlot::new(slot as usize)),
+                                        },
+                                    ));
+                                }
+                                None => {
+                                    return Err(RegAllocError::SSA(vreg, inst));
+                                }
+                            }
+                        }
+
+                        // No register available
+                        // TODO: try to evict vreg that does not need to be in a preg
+                        return Err(RegAllocError::TooManyLiveRegs);
+                    }
+                    OperandConstraint::Any | OperandConstraint::Stack => {
+                        // alloc stack slot
+                        let size = if op.class() == RegClass::Int {
+                            slot_size_int
+                        } else {
+                            slot_size_float
+                        };
+                        let slot = state.cur_stack_slot_idx;
+                        state.cur_stack_slot_idx += size;
+                        state.vregs[vreg_idx].stack_slot = Some(slot);
+                        state.allocs[alloc_idx + i] =
+                            Allocation::stack(SpillSlot::new(slot as usize));
+                    }
+                    OperandConstraint::Reuse(op_idx) => {
+                        let alloc = state.allocs[alloc_idx + op_idx];
+                        if alloc.is_none() || operands[op_idx].pos() == OperandPos::Late {
+                            panic!("Invalid reuse");
+                        }
+
+                        state.allocs[alloc_idx + i] = alloc;
+                        if let Some(alloc) = alloc.as_stack() {
+                            state.vregs[vreg_idx].stack_slot = Some(alloc.index() as u32);
+                            state.vregs[operands[op_idx].vreg().vreg()].stack_slot = None;
+                        } else if let Some(reg) = alloc.as_reg() {
+                            state.vregs[operands[op_idx].vreg().vreg()].cur_reg = None;
+                            state.vregs[vreg_idx].cur_reg = Some(reg);
+
+                            // alloc stack slot
+                            let size = if op.class() == RegClass::Int {
+                                slot_size_int
+                            } else {
+                                slot_size_float
+                            };
+                            let slot = state.cur_stack_slot_idx;
+                            state.cur_stack_slot_idx += size;
+                            state.vregs[vreg_idx].stack_slot = Some(slot);
+
+                            // move to stack after inst
+                            state.edits.push((
+                                ProgPoint::after(inst),
+                                Edit::Move {
+                                    from: Allocation::reg(reg),
+                                    to: Allocation::stack(SpillSlot::new(slot as usize)),
+                                },
+                            ));
+                        }
+                    }
+                    OperandConstraint::FixedReg(_) => continue,
+                }
+            }
+        }
+    }
+
+    todo!("")
+}

src/ion/mod.rs

@@ -39,6 +39,7 @@ pub(crate) mod dump;
 pub(crate) mod moves;
 pub(crate) mod spill;
 pub(crate) mod stackmap;
+mod fast_alloc;
 
 impl<'a, F: Function> Env<'a, F> {
     pub(crate) fn new(
@@ -120,13 +121,18 @@ pub fn run<F: Function>(
     mach_env: &MachineEnv,
     enable_annotations: bool,
     enable_ssa_checker: bool,
+    use_fast_alloc: bool,
 ) -> Result<Output, RegAllocError> {
-    let cfginfo = CFGInfo::new(func)?;
+    let cfginfo = CFGInfo::new(func, !use_fast_alloc)?;
 
     if enable_ssa_checker {
         validate_ssa(func, &cfginfo)?;
     }
 
+    if use_fast_alloc {
+        return fast_alloc::run(func, mach_env, cfginfo);
+    }
+
     let mut env = Env::new(func, mach_env, cfginfo, enable_annotations);
     env.init()?;
 

src/lib.rs

@@ -1491,7 +1491,7 @@ pub fn run<F: Function>(
     env: &MachineEnv,
     options: &RegallocOptions,
 ) -> Result<Output, RegAllocError> {
-    ion::run(func, env, options.verbose_log, options.validate_ssa)
+    ion::run(func, env, options.verbose_log, options.validate_ssa, options.fast_alloc)
 }
 
 /// Options for allocation.
@@ -1502,4 +1502,7 @@ pub struct RegallocOptions {
 
     /// Run the SSA validator before allocating registers.
     pub validate_ssa: bool,
+
+    /// Use a fast algorithm that may return suboptimal results.
+    pub fast_alloc: bool,
 }