diff --git a/src/asmgen/mod.rs b/src/asmgen/mod.rs
index c2a1ffe..edf0652 100644
--- a/src/asmgen/mod.rs
+++ b/src/asmgen/mod.rs
@@ -5,7 +5,7 @@ use std::ops::Deref;
 use lang_c::ast;
 
 use crate::ir::HasDtype;
-use crate::opt::opt_utils;
+use crate::opt::opt_utils::*;
 use crate::{Translate, asm, ir};
 
 #[derive(Debug, Default)]
@@ -35,6 +35,167 @@ impl Translate<ir::TranslationUnit> for Asmgen {
     }
 }
 
+struct InferenceGraph {
+    edges: HashSet<(ir::RegisterId, ir::RegisterId)>,
+}
+
+impl InferenceGraph {
+    fn new(code: &ir::FunctionDefinition) -> Self {
+        let cfg = make_cfg(code);
+        let reverse_cfg = reverse_cfg(&cfg);
+        let domtree = Domtree::new(code.bid_init, &cfg, &reverse_cfg);
+
+        let mut lives = HashMap::new();
+
+        loop {
+            let mut changed = false;
+
+            for bid in domtree.rpo() {
+                let block = &code.blocks[bid];
+                let len = block.instructions.len();
+                let mut uses = HashSet::new();
+
+                for (i, inst) in block.instructions.iter().enumerate() {
+                    match inst.deref() {
+                        ir::Instruction::BinOp { lhs, rhs, .. } => {
+                            mark_as_used(lhs, &mut uses);
+                            mark_as_used(rhs, &mut uses);
+                        }
+                        ir::Instruction::UnaryOp { operand, .. } => {
+                            mark_as_used(operand, &mut uses);
+                        }
+                        ir::Instruction::Store { ptr, value } => {
+                            mark_as_used(ptr, &mut uses);
+                            mark_as_used(value, &mut uses);
+                        }
+                        ir::Instruction::Load { ptr } => {
+                            mark_as_used(ptr, &mut uses);
+                        }
+                        ir::Instruction::Call { callee, args, .. } => {
+                            mark_as_used(callee, &mut uses);
+                            for arg in args {
+                                mark_as_used(arg, &mut uses);
+                            }
+                        }
+                        ir::Instruction::TypeCast { value, .. } => {
+                            mark_as_used(value, &mut uses);
+                        }
+                        ir::Instruction::GetElementPtr { ptr, offset, .. } => {
+                            mark_as_used(ptr, &mut uses);
+                            mark_as_used(offset, &mut uses);
+                        }
+                        _ => (),
+                    }
+
+                    let mut next_lives = lives
+                        .entry(ir::RegisterId::temp(*bid, i + 1))
+                        .or_insert_with(HashSet::new)
+                        .clone();
+                    let _ = next_lives.remove(&ir::RegisterId::temp(*bid, i));
+                    uses.extend(next_lives);
+                    changed = extend_set(
+                        lives
+                            .entry(ir::RegisterId::temp(*bid, i))
+                            .or_insert_with(HashSet::new),
+                        std::mem::take(&mut uses),
+                    ) || changed;
+                }
+
+                let mut uses = HashSet::new();
+                match &block.exit {
+                    ir::BlockExit::Jump { arg } => {
+                        for arg in &arg.args {
+                            mark_as_used(arg, &mut uses);
+                        }
+                    }
+                    ir::BlockExit::ConditionalJump {
+                        condition,
+                        arg_then,
+                        arg_else,
+                    } => {
+                        mark_as_used(condition, &mut uses);
+                        for arg in &arg_then.args {
+                            mark_as_used(arg, &mut uses);
+                        }
+                        for arg in &arg_else.args {
+                            mark_as_used(arg, &mut uses);
+                        }
+                    }
+                    ir::BlockExit::Switch {
+                        value,
+                        default,
+                        cases,
+                    } => {
+                        mark_as_used(value, &mut uses);
+                        for arg in &default.args {
+                            mark_as_used(arg, &mut uses);
+                        }
+                        for (_, arg) in cases {
+                            for arg in &arg.args {
+                                mark_as_used(arg, &mut uses);
+                            }
+                        }
+                    }
+                    ir::BlockExit::Return { value } => {
+                        mark_as_used(value, &mut uses);
+                    }
+                    _ => (),
+                }
+
+                let successors = cfg[bid].iter().map(|arg| arg.bid).collect::<Vec<_>>();
+                let mut successor_lives = HashSet::<ir::RegisterId>::new();
+                for succ in &successors {
+                    if let Some(succ_lives) = lives.get(&ir::RegisterId::temp(*succ, 0)) {
+                        successor_lives.extend(succ_lives);
+                    }
+                }
+
+                uses.extend(successor_lives);
+                changed = extend_set(
+                    lives
+                        .entry(ir::RegisterId::temp(*bid, len))
+                        .or_insert_with(HashSet::new),
+                    uses,
+                ) || changed;
+            }
+
+            if !changed {
+                break;
+            }
+        }
+
+        let mut edges = HashSet::new();
+
+        for (_, lives) in &lives {
+            for rid1 in lives {
+                for rid2 in lives {
+                    if rid1 != rid2 {
+                        let _ = edges.insert((*rid1, *rid2));
+                    }
+                }
+            }
+        }
+
+        println!("Inference graph: {:?}", edges);
+
+        InferenceGraph { edges }
+    }
+}
+
+fn mark_as_used(operand: &ir::Operand, uses: &mut HashSet<ir::RegisterId>) {
+    if let ir::Operand::Register { rid, .. } = operand {
+        if !matches!(rid, ir::RegisterId::Local { .. }) {
+            let _ = uses.insert(*rid);
+        }
+    }
+}
+
+fn extend_set(set: &mut HashSet<ir::RegisterId>, other: HashSet<ir::RegisterId>) -> bool {
+    let len = set.len();
+    set.extend(other);
+    set.len() != len
+}
+
 struct Context {
     insts: Vec<asm::Instruction>,
     stack_offsets: HashMap<ir::RegisterId, u64>,
@@ -95,6 +256,9 @@ impl Asmgen {
                 definition,
             } => {
                 if let Some(definition) = definition {
+                    // TEMP
+                    let graph = InferenceGraph::new(definition);
+
                     let mut context = self.translate_prologue(signature, definition, structs);
                     self.translate_block(
                         name,
diff --git a/src/opt/opt_utils.rs b/src/opt/opt_utils.rs
index ff69108..dcf2fe2 100644
--- a/src/opt/opt_utils.rs
+++ b/src/opt/opt_utils.rs
@@ -122,7 +122,7 @@ impl Domtree {
             };
             for (bid_pred, _) in preds {
                 let mut runner = *bid_pred;
-                while !Self::dominates(&idoms, runner, *bid) {
+                while idoms.contains_key(&runner) && !Self::dominates(&idoms, runner, *bid) {
                     frontiers.entry(runner).or_insert_with(Vec::new).push(*bid);
                     runner = idoms[&runner];
                 }