diff --git a/library/init/lean/compiler/default.lean b/library/init/lean/compiler/default.lean
index 2471fdf327..49b7aa508b 100644
--- a/library/init/lean/compiler/default.lean
+++ b/library/init/lean/compiler/default.lean
@@ -10,6 +10,7 @@ import init.lean.compiler.pushproj
 import init.lean.compiler.elimdead
 import init.lean.compiler.simpcase
 import init.lean.compiler.resetreuse
+import init.lean.compiler.normids
 namespace Lean
 namespace IR
 
@@ -30,6 +31,9 @@ do
    let d := d.simpCase,
    IO.println "=== After simplify case ===",
    IO.println d,
+   let d := d.normalizeIds,
+   IO.println "=== After normalize Ids ===",
+   IO.println d,
    pure ()
 
 end IR
diff --git a/library/init/lean/compiler/ir.lean b/library/init/lean/compiler/ir.lean
index aa4afea26e..909c83956f 100644
--- a/library/init/lean/compiler/ir.lean
+++ b/library/init/lean/compiler/ir.lean
@@ -89,6 +89,8 @@ inductive Arg
 | var (id : VarId)
 | irrelevant
 
+instance argInh : Inhabited Arg := ⟨Arg.irrelevant⟩
+
 @[export lean.ir.mk_var_arg_core] def mkVarArg (id : VarId) : Arg := Arg.var id
 @[export lean.ir.mk_irrelevant_arg_core] def mkIrrelevantArg : Arg := Arg.irrelevant
 
@@ -164,6 +166,8 @@ inductive Expr
 structure Param :=
 (x : VarId) (borrowed : Bool) (ty : IRType)
 
+instance paramInh : Inhabited Param := ⟨{ x := { idx := 0 }, borrowed := false, ty := IRType.object }⟩
+
 @[export lean.ir.mk_param_core] def mkParam (x : VarId) (borrowed : Bool) (ty : IRType) : Param := ⟨x, borrowed, ty⟩
 
 inductive AltCore (FnBody : Type) : Type
diff --git a/library/init/lean/compiler/normids.lean b/library/init/lean/compiler/normids.lean
new file mode 100644
index 0000000000..12d74a2edb
--- /dev/null
+++ b/library/init/lean/compiler/normids.lean
@@ -0,0 +1,105 @@
+/-
+Copyright (c) 2019 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Leonardo de Moura
+-/
+prelude
+import init.lean.compiler.ir init.control.reader
+
+namespace Lean
+namespace IR
+namespace NormalizeIds
+
+abbrev M := ReaderT IndexRenaming Id
+
+def normIndex (x : Index) : M Index :=
+λ m, match m.find x with
+| some y := y
+| none   := x
+
+def normVar (x : VarId) : M VarId :=
+VarId.mk <$> normIndex x.idx
+
+def normJP (x : JoinPointId) : M JoinPointId :=
+JoinPointId.mk <$> normIndex x.idx
+
+def normArg : Arg → M Arg
+| (Arg.var x) := Arg.var <$> normVar x
+| other       := pure other
+
+def normArgs (as : Array Arg) : M (Array Arg) :=
+λ m, as.hmap $ λ a, normArg a m
+
+def normExpr : Expr → M Expr
+| (Expr.ctor c ys)      m := Expr.ctor c (normArgs ys m)
+| (Expr.reset x)        m := Expr.reset (normVar x m)
+| (Expr.reuse x c u ys) m := Expr.reuse (normVar x m) c u (normArgs ys m)
+| (Expr.proj i x)       m := Expr.proj i (normVar x m)
+| (Expr.uproj i x)      m := Expr.uproj i (normVar x m)
+| (Expr.sproj n o x)    m := Expr.sproj n o (normVar x m)
+| (Expr.fap c ys)       m := Expr.fap c (normArgs ys m)
+| (Expr.pap c ys)       m := Expr.pap c (normArgs ys m)
+| (Expr.ap x ys)        m := Expr.ap (normVar x m) (normArgs ys m)
+| (Expr.box t x)        m := Expr.box t (normVar x m)
+| (Expr.unbox x)        m := Expr.unbox (normVar x m)
+| (Expr.isShared x)     m := Expr.isShared (normVar x m)
+| (Expr.isTaggedPtr x)  m := Expr.isTaggedPtr (normVar x m)
+| e@(Expr.lit v)        m :=  e
+
+abbrev N := ReaderT IndexRenaming (State Nat)
+
+def mkFresh : N Index :=
+getModify (+1)
+
+@[inline] def withVar {α : Type} (x : VarId) (k : VarId → N α) : N α :=
+λ m, do
+  n ← getModify (+1),
+  k { idx := n } (m.insert x.idx n)
+
+@[inline] def withJP {α : Type} (x : JoinPointId) (k : JoinPointId → N α) : N α :=
+λ m, do
+  n ← getModify (+1),
+  k { idx := n } (m.insert x.idx n)
+
+@[inline] def withParams {α : Type} (ps : Array Param) (k : Array Param → N α) : N α :=
+λ m, do
+  m ← ps.mfoldl m (λ m p, do n ← getModify (+1), pure $ m.insert p.x.idx n),
+  let ps := ps.hmap $ λ p, { x := normVar p.x m, .. p },
+  k ps m
+
+instance MtoN {α} : HasCoe (M α) (N α) :=
+⟨λ x m, pure $ x m⟩
+
+local attribute [instance] monadInhabited
+
+partial def normFnBody : FnBody → N FnBody
+| (FnBody.vdecl x t v b)     := do v ← normExpr v, withVar x $ λ x, FnBody.vdecl x t v <$> normFnBody b
+| (FnBody.jdecl j ys t v b)  := do
+  (ys, v) ← withParams ys $ λ ys, do { v ← normFnBody v, pure (ys, v) },
+  withJP j $ λ j, FnBody.jdecl j ys t v <$> normFnBody b
+| (FnBody.set x i y b)       := do x ← normVar x, y ← normVar y, FnBody.set x i y <$> normFnBody b
+| (FnBody.uset x i y b)      := do x ← normVar x, y ← normVar y, FnBody.uset x i y <$> normFnBody b
+| (FnBody.sset x i o y t b)  := do x ← normVar x, y ← normVar y, FnBody.sset x i o y t <$> normFnBody b
+| (FnBody.release x i b)     := do x ← normVar x, FnBody.release x i <$> normFnBody b
+| (FnBody.inc x n c b)       := do x ← normVar x, FnBody.inc x n c <$> normFnBody b
+| (FnBody.dec x n c b)       := do x ← normVar x, FnBody.dec x n c <$> normFnBody b
+| (FnBody.mdata d b)         := FnBody.mdata d <$> normFnBody b
+| (FnBody.case tid x alts)   := do
+  x ← normVar x,
+  alts ← alts.hmmap $ λ alt, alt.mmodifyBody normFnBody,
+  pure $ FnBody.case tid x alts
+| (FnBody.jmp j ys)         := FnBody.jmp <$> normJP j <*> normArgs ys
+| (FnBody.ret x)            := FnBody.ret <$> normArg x
+| FnBody.unreachable        := pure FnBody.unreachable
+
+def normDecl : Decl → N Decl
+| (Decl.fdecl f xs t b) := withParams xs $ λ xs, Decl.fdecl f xs t <$> normFnBody b
+| other                 := pure other
+
+end NormalizeIds
+
+def Decl.normalizeIds (d : Decl) : Decl :=
+(NormalizeIds.normDecl d {}).run' 1
+
+end IR
+end Lean