Phantom let support in Cmm (#2070)

Author: mshinwell

.depend

@@ -213,8 +213,10 @@ typing/envaux.cmo : typing/subst.cmi typing/printtyp.cmi typing/path.cmi \
 typing/envaux.cmx : typing/subst.cmx typing/printtyp.cmx typing/path.cmx \
     typing/ident.cmx typing/env.cmx typing/envaux.cmi
 typing/envaux.cmi : typing/subst.cmi typing/path.cmi typing/env.cmi
-typing/ident.cmo : utils/identifiable.cmi utils/clflags.cmi typing/ident.cmi
-typing/ident.cmx : utils/identifiable.cmx utils/clflags.cmx typing/ident.cmi
+typing/ident.cmo : utils/misc.cmi utils/identifiable.cmi utils/clflags.cmi \
+    typing/ident.cmi
+typing/ident.cmx : utils/misc.cmx utils/identifiable.cmx utils/clflags.cmx \
+    typing/ident.cmi
 typing/ident.cmi : utils/identifiable.cmi
 typing/includeclass.cmo : typing/types.cmi typing/printtyp.cmi \
     typing/path.cmi typing/ctype.cmi parsing/builtin_attributes.cmi \
@@ -308,17 +310,17 @@ typing/printpat.cmi : typing/typedtree.cmi parsing/asttypes.cmi
 typing/printtyp.cmo : utils/warnings.cmi typing/types.cmi \
     typing/primitive.cmi typing/predef.cmi typing/path.cmi \
     parsing/parsetree.cmi typing/outcometree.cmi typing/oprint.cmi \
-    utils/numbers.cmi utils/misc.cmi parsing/longident.cmi \
-    parsing/location.cmi typing/ident.cmi typing/env.cmi typing/ctype.cmi \
-    utils/clflags.cmi parsing/builtin_attributes.cmi typing/btype.cmi \
-    parsing/asttypes.cmi typing/printtyp.cmi
+    utils/misc.cmi parsing/longident.cmi parsing/location.cmi \
+    typing/ident.cmi typing/env.cmi typing/ctype.cmi utils/clflags.cmi \
+    parsing/builtin_attributes.cmi typing/btype.cmi parsing/asttypes.cmi \
+    typing/printtyp.cmi
 typing/printtyp.cmx : utils/warnings.cmx typing/types.cmx \
     typing/primitive.cmx typing/predef.cmx typing/path.cmx \
     parsing/parsetree.cmi typing/outcometree.cmi typing/oprint.cmx \
-    utils/numbers.cmx utils/misc.cmx parsing/longident.cmx \
-    parsing/location.cmx typing/ident.cmx typing/env.cmx typing/ctype.cmx \
-    utils/clflags.cmx parsing/builtin_attributes.cmx typing/btype.cmx \
-    parsing/asttypes.cmi typing/printtyp.cmi
+    utils/misc.cmx parsing/longident.cmx parsing/location.cmx \
+    typing/ident.cmx typing/env.cmx typing/ctype.cmx utils/clflags.cmx \
+    parsing/builtin_attributes.cmx typing/btype.cmx parsing/asttypes.cmi \
+    typing/printtyp.cmi
 typing/printtyp.cmi : typing/types.cmi typing/path.cmi \
     typing/outcometree.cmi parsing/longident.cmi parsing/location.cmi \
     typing/ident.cmi typing/env.cmi parsing/asttypes.cmi
@@ -836,10 +838,10 @@ asmcomp/asmpackager.cmx : typing/typemod.cmx bytecomp/translmod.cmx \
     utils/clflags.cmx utils/ccomp.cmx asmcomp/asmlink.cmx asmcomp/asmgen.cmx \
     asmcomp/asmpackager.cmi
 asmcomp/asmpackager.cmi : typing/env.cmi middle_end/backend_intf.cmi
-asmcomp/backend_var.cmo : typing/printtyp.cmi typing/path.cmi \
-    typing/ident.cmi middle_end/debuginfo.cmi asmcomp/backend_var.cmi
-asmcomp/backend_var.cmx : typing/printtyp.cmx typing/path.cmx \
-    typing/ident.cmx middle_end/debuginfo.cmx asmcomp/backend_var.cmi
+asmcomp/backend_var.cmo : typing/path.cmi typing/ident.cmi \
+    middle_end/debuginfo.cmi asmcomp/backend_var.cmi
+asmcomp/backend_var.cmx : typing/path.cmx typing/ident.cmx \
+    middle_end/debuginfo.cmx asmcomp/backend_var.cmi
 asmcomp/backend_var.cmi : typing/path.cmi typing/ident.cmi \
     middle_end/debuginfo.cmi
 asmcomp/branch_relaxation.cmo : utils/misc.cmi asmcomp/mach.cmi \
@@ -891,14 +893,14 @@ asmcomp/clambda.cmi : bytecomp/lambda.cmi middle_end/debuginfo.cmi \
 asmcomp/closure.cmo : utils/warnings.cmi bytecomp/switch.cmi \
     bytecomp/simplif.cmi bytecomp/semantics_of_primitives.cmi \
     typing/primitive.cmi utils/numbers.cmi utils/misc.cmi \
-    parsing/location.cmi bytecomp/lambda.cmi typing/env.cmi \
+    parsing/location.cmi bytecomp/lambda.cmi typing/ident.cmi typing/env.cmi \
     middle_end/debuginfo.cmi utils/config.cmi asmcomp/compilenv.cmi \
     utils/clflags.cmi asmcomp/clambda.cmi asmcomp/backend_var.cmi \
     parsing/asttypes.cmi asmcomp/arch.cmo asmcomp/closure.cmi
 asmcomp/closure.cmx : utils/warnings.cmx bytecomp/switch.cmx \
     bytecomp/simplif.cmx bytecomp/semantics_of_primitives.cmx \
     typing/primitive.cmx utils/numbers.cmx utils/misc.cmx \
-    parsing/location.cmx bytecomp/lambda.cmx typing/env.cmx \
+    parsing/location.cmx bytecomp/lambda.cmx typing/ident.cmx typing/env.cmx \
     middle_end/debuginfo.cmx utils/config.cmx asmcomp/compilenv.cmx \
     utils/clflags.cmx asmcomp/clambda.cmx asmcomp/backend_var.cmx \
     parsing/asttypes.cmi asmcomp/arch.cmx asmcomp/closure.cmi
@@ -914,13 +916,13 @@ asmcomp/closure_offsets.cmx : middle_end/base_types/variable.cmx \
 asmcomp/closure_offsets.cmi : middle_end/base_types/var_within_closure.cmi \
     middle_end/flambda.cmi middle_end/base_types/closure_id.cmi
 asmcomp/cmm.cmo : bytecomp/lambda.cmi middle_end/debuginfo.cmi \
-    asmcomp/backend_var.cmi parsing/asttypes.cmi asmcomp/arch.cmo \
-    asmcomp/cmm.cmi
+    asmcomp/clambda.cmi asmcomp/backend_var.cmi parsing/asttypes.cmi \
+    asmcomp/arch.cmo asmcomp/cmm.cmi
 asmcomp/cmm.cmx : bytecomp/lambda.cmx middle_end/debuginfo.cmx \
-    asmcomp/backend_var.cmx parsing/asttypes.cmi asmcomp/arch.cmx \
-    asmcomp/cmm.cmi
+    asmcomp/clambda.cmx asmcomp/backend_var.cmx parsing/asttypes.cmi \
+    asmcomp/arch.cmx asmcomp/cmm.cmi
 asmcomp/cmm.cmi : bytecomp/lambda.cmi middle_end/debuginfo.cmi \
-    asmcomp/backend_var.cmi parsing/asttypes.cmi
+    asmcomp/clambda.cmi asmcomp/backend_var.cmi parsing/asttypes.cmi
 asmcomp/cmmgen.cmo : asmcomp/un_anf.cmi typing/types.cmi bytecomp/switch.cmi \
     asmcomp/strmatch.cmi asmcomp/proc.cmi bytecomp/printlambda.cmi \
     typing/primitive.cmi utils/numbers.cmi utils/misc.cmi bytecomp/lambda.cmi \
@@ -1130,18 +1132,18 @@ asmcomp/mach.cmi : asmcomp/debug/reg_availability_set.cmi asmcomp/reg.cmi \
     middle_end/debuginfo.cmi asmcomp/cmm.cmi asmcomp/backend_var.cmi \
     asmcomp/arch.cmo
 asmcomp/printclambda.cmo : bytecomp/printlambda.cmi bytecomp/lambda.cmi \
-    asmcomp/clambda.cmi asmcomp/backend_var.cmi parsing/asttypes.cmi \
-    asmcomp/printclambda.cmi
+    typing/ident.cmi asmcomp/clambda.cmi asmcomp/backend_var.cmi \
+    parsing/asttypes.cmi asmcomp/printclambda.cmi
 asmcomp/printclambda.cmx : bytecomp/printlambda.cmx bytecomp/lambda.cmx \
-    asmcomp/clambda.cmx asmcomp/backend_var.cmx parsing/asttypes.cmi \
-    asmcomp/printclambda.cmi
+    typing/ident.cmx asmcomp/clambda.cmx asmcomp/backend_var.cmx \
+    parsing/asttypes.cmi asmcomp/printclambda.cmi
 asmcomp/printclambda.cmi : asmcomp/clambda.cmi
-asmcomp/printcmm.cmo : bytecomp/lambda.cmi middle_end/debuginfo.cmi \
-    asmcomp/cmm.cmi asmcomp/backend_var.cmi parsing/asttypes.cmi \
-    asmcomp/printcmm.cmi
-asmcomp/printcmm.cmx : bytecomp/lambda.cmx middle_end/debuginfo.cmx \
-    asmcomp/cmm.cmx asmcomp/backend_var.cmx parsing/asttypes.cmi \
-    asmcomp/printcmm.cmi
+asmcomp/printcmm.cmo : asmcomp/printclambda.cmi bytecomp/lambda.cmi \
+    middle_end/debuginfo.cmi asmcomp/cmm.cmi asmcomp/backend_var.cmi \
+    parsing/asttypes.cmi asmcomp/printcmm.cmi
+asmcomp/printcmm.cmx : asmcomp/printclambda.cmx bytecomp/lambda.cmx \
+    middle_end/debuginfo.cmx asmcomp/cmm.cmx asmcomp/backend_var.cmx \
+    parsing/asttypes.cmi asmcomp/printcmm.cmi
 asmcomp/printcmm.cmi : middle_end/debuginfo.cmi asmcomp/cmm.cmi
 asmcomp/printlinear.cmo : asmcomp/printmach.cmi asmcomp/printcmm.cmi \
     asmcomp/mach.cmi asmcomp/linearize.cmi middle_end/debuginfo.cmi \
@@ -2460,14 +2462,14 @@ toplevel/genprintval.cmi : typing/types.cmi typing/path.cmi \
     typing/outcometree.cmi typing/env.cmi
 toplevel/opttopdirs.cmo : utils/warnings.cmi typing/types.cmi \
     typing/printtyp.cmi toplevel/opttoploop.cmi utils/misc.cmi \
-    parsing/longident.cmi typing/ident.cmi typing/env.cmi typing/ctype.cmi \
-    utils/config.cmi driver/compdynlink.cmi utils/clflags.cmi \
-    asmcomp/asmlink.cmi toplevel/opttopdirs.cmi
+    parsing/longident.cmi typing/env.cmi typing/ctype.cmi utils/config.cmi \
+    driver/compdynlink.cmi utils/clflags.cmi asmcomp/asmlink.cmi \
+    toplevel/opttopdirs.cmi
 toplevel/opttopdirs.cmx : utils/warnings.cmx typing/types.cmx \
     typing/printtyp.cmx toplevel/opttoploop.cmx utils/misc.cmx \
-    parsing/longident.cmx typing/ident.cmx typing/env.cmx typing/ctype.cmx \
-    utils/config.cmx driver/compdynlink.cmi utils/clflags.cmx \
-    asmcomp/asmlink.cmx toplevel/opttopdirs.cmi
+    parsing/longident.cmx typing/env.cmx typing/ctype.cmx utils/config.cmx \
+    driver/compdynlink.cmi utils/clflags.cmx asmcomp/asmlink.cmx \
+    toplevel/opttopdirs.cmi
 toplevel/opttopdirs.cmi : parsing/longident.cmi
 toplevel/opttoploop.cmo : utils/warnings.cmi typing/types.cmi \
     typing/typemod.cmi typing/typedtree.cmi typing/typecore.cmi \

Changes

@@ -437,6 +437,12 @@ Working version
 - GPR#2065: Add [Proc.destroyed_at_reloadretaddr].
   (Mark Shinwell, review by Damien Doligez)
 
+- GPR#2060: "Phantom let" support for the Clambda language.
+  (Mark Shinwell, review by Vincent Laviron)
+
+- GPR#2070: "Phantom let" support for the Cmm language.
+  (Mark Shinwell, review by Vincent Laviron)
+
 - GPR#2072: Always associate a scope to a type
   (Thomas Refis, review by Jacques Garrigue and Leo White)
 

asmcomp/afl_instrument.ml

@@ -68,6 +68,8 @@ and instrument = function
 
   (* these cases add no logging, but instrument subexpressions *)
   | Clet (v, e, body) -> Clet (v, instrument e, instrument body)
+  | Cphantom_let (v, defining_expr, body) ->
+    Cphantom_let (v, defining_expr, instrument body)
   | Cassign (v, e) -> Cassign (v, instrument e)
   | Ctuple es -> Ctuple (List.map instrument es)
   | Cop (op, es, dbg) -> Cop (op, List.map instrument es, dbg)

asmcomp/clambda.ml

@@ -41,7 +41,7 @@ and uphantom_defining_expr =
   | Uphantom_var of Backend_var.t
   | Uphantom_offset_var of { var : Backend_var.t; offset_in_words : int; }
   | Uphantom_read_field of { var : Backend_var.t; field : int; }
-  | Uphantom_read_symbol_field of { sym : uconstant; field : int; }
+  | Uphantom_read_symbol_field of { sym : string; field : int; }
   | Uphantom_block of { tag : int; fields : Backend_var.t list; }
 
 and ulambda =

asmcomp/clambda.mli

@@ -48,7 +48,7 @@ and uphantom_defining_expr =
   (** The phantom-let-bound-variable's value is found by adding the given
       number of words to the pointer contained in the given identifier, then
       dereferencing. *)
-  | Uphantom_read_symbol_field of { sym : uconstant; field : int; }
+  | Uphantom_read_symbol_field of { sym : string; field : int; }
   (** As for [Uphantom_read_var_field], but with the pointer specified by
       a symbol. *)
   | Uphantom_block of { tag : int; fields : Backend_var.t list; }

asmcomp/cmm.ml

@@ -116,6 +116,15 @@ type raise_kind =
 
 type rec_flag = Nonrecursive | Recursive
 
+type phantom_defining_expr =
+  | Cphantom_const_int of Targetint.t
+  | Cphantom_const_symbol of string
+  | Cphantom_var of Backend_var.t
+  | Cphantom_offset_var of { var : Backend_var.t; offset_in_words : int; }
+  | Cphantom_read_field of { var : Backend_var.t; field : int; }
+  | Cphantom_read_symbol_field of { sym : string; field : int; }
+  | Cphantom_block of { tag : int; fields : Backend_var.t list; }
+
 type memory_chunk =
     Byte_unsigned
   | Byte_signed
@@ -159,6 +168,8 @@ type expression =
   | Cblockheader of nativeint * Debuginfo.t
   | Cvar of Backend_var.t
   | Clet of Backend_var.With_provenance.t * expression * expression
+  | Cphantom_let of Backend_var.With_provenance.t
+      * phantom_defining_expr option * expression
   | Cassign of Backend_var.t * expression
   | Ctuple of expression list
   | Cop of operation * expression list * Debuginfo.t

asmcomp/cmm.mli

@@ -93,6 +93,33 @@ type raise_kind =
 
 type rec_flag = Nonrecursive | Recursive
 
+type phantom_defining_expr =
+  (* CR-soon mshinwell: Convert this to [Targetint.OCaml.t] (or whatever the
+     representation of "target-width OCaml integers of type [int]"
+     becomes when merged). *)
+  | Cphantom_const_int of Targetint.t
+  (** The phantom-let-bound variable is a constant integer.
+      The argument must be the tagged representation of an integer within
+      the range of type [int] on the target.  (Analogously to [Cconst_int].) *)
+  | Cphantom_const_symbol of string
+  (** The phantom-let-bound variable is an alias for a symbol. *)
+  | Cphantom_var of Backend_var.t
+  (** The phantom-let-bound variable is an alias for another variable.  The
+      aliased variable must not be a bound by a phantom let. *)
+  | Cphantom_offset_var of { var : Backend_var.t; offset_in_words : int; }
+  (** The phantom-let-bound-variable's value is defined by adding the given
+      number of words to the pointer contained in the given identifier. *)
+  | Cphantom_read_field of { var : Backend_var.t; field : int; }
+  (** The phantom-let-bound-variable's value is found by adding the given
+      number of words to the pointer contained in the given identifier, then
+      dereferencing. *)
+  | Cphantom_read_symbol_field of { sym : string; field : int; }
+  (** As for [Uphantom_read_var_field], but with the pointer specified by
+      a symbol. *)
+  | Cphantom_block of { tag : int; fields : Backend_var.t list; }
+  (** The phantom-let-bound variable points at a block with the given
+      structure. *)
+
 type memory_chunk =
     Byte_unsigned
   | Byte_signed
@@ -139,6 +166,8 @@ and expression =
   | Cblockheader of nativeint * Debuginfo.t
   | Cvar of Backend_var.t
   | Clet of Backend_var.With_provenance.t * expression * expression
+  | Cphantom_let of Backend_var.With_provenance.t
+      * phantom_defining_expr option * expression
   | Cassign of Backend_var.t * expression
   | Ctuple of expression list
   | Cop of operation * expression list * Debuginfo.t

asmcomp/cmmgen.ml

@@ -133,6 +133,10 @@ let int_const n =
 let cint_const n =
   Cint(Nativeint.add (Nativeint.shift_left (Nativeint.of_int n) 1) 1n)
 
+let targetint_const n =
+  Targetint.add (Targetint.shift_left (Targetint.of_int n) 1)
+    Targetint.one
+
 let add_no_overflow n x c dbg =
   let d = n + x in
   if d = 0 then c else Cop(Caddi, [c; Cconst_int d], dbg)
@@ -1789,7 +1793,30 @@ let rec transl env e =
               (call_met obj args))
   | Ulet(str, kind, id, exp, body) ->
       transl_let env str kind id exp body
-  | Uphantom_let (_var, _defining_expr, body) -> transl env body
+  | Uphantom_let (var, defining_expr, body) ->
+      let defining_expr =
+        match defining_expr with
+        | None -> None
+        | Some defining_expr ->
+          let defining_expr =
+            match defining_expr with
+            | Uphantom_const (Uconst_ref (sym, _defining_expr)) ->
+              Cphantom_const_symbol sym
+            | Uphantom_read_symbol_field { sym; field; } ->
+              Cphantom_read_symbol_field { sym; field; }
+            | Uphantom_const (Uconst_int i) | Uphantom_const (Uconst_ptr i) ->
+              Cphantom_const_int (targetint_const i)
+            | Uphantom_var var -> Cphantom_var var
+            | Uphantom_read_field { var; field; } ->
+              Cphantom_read_field { var; field; }
+            | Uphantom_offset_var { var; offset_in_words; } ->
+              Cphantom_offset_var { var; offset_in_words; }
+            | Uphantom_block { tag; fields; } ->
+              Cphantom_block { tag; fields; }
+          in
+          Some defining_expr
+      in
+      Cphantom_let (var, defining_expr, transl env body)
   | Uletrec(bindings, body) ->
       transl_letrec env bindings (transl env body)
 

asmcomp/printclambda.ml

@@ -71,7 +71,7 @@ and phantom_defining_expr ppf = function
   | Uphantom_read_field { var; field; } ->
     Format.fprintf ppf "%a[%d]" Backend_var.print var field
   | Uphantom_read_symbol_field { sym; field; } ->
-    Format.fprintf ppf "%a[%d]" uconstant sym field
+    Format.fprintf ppf "%s[%d]" sym field
   | Uphantom_block { tag; fields; } ->
     Format.fprintf ppf "[%d: " tag;
     List.iter (fun field ->

asmcomp/printclambda.mli

@@ -19,3 +19,8 @@ open Format
 val clambda: formatter -> ulambda -> unit
 val approx: formatter -> value_approximation -> unit
 val structured_constant: formatter -> ustructured_constant -> unit
+
+val phantom_defining_expr_opt
+   : formatter
+  -> uphantom_defining_expr option
+  -> unit

asmcomp/printcmm.ml

@@ -76,6 +76,29 @@ let raise_kind fmt = function
   | Raise_withtrace -> Format.fprintf fmt "raise_withtrace"
   | Raise_notrace -> Format.fprintf fmt "raise_notrace"
 
+let phantom_defining_expr ppf defining_expr =
+  match defining_expr with
+  | Cphantom_const_int i -> Targetint.print ppf i
+  | Cphantom_const_symbol sym -> Format.pp_print_string ppf sym
+  | Cphantom_var var -> V.print ppf var
+  | Cphantom_offset_var { var; offset_in_words; } ->
+    Format.fprintf ppf "%a+(%d)" V.print var offset_in_words
+  | Cphantom_read_field { var; field; } ->
+    Format.fprintf ppf "%a[%d]" V.print var field
+  | Cphantom_read_symbol_field { sym; field; } ->
+    Format.fprintf ppf "%s[%d]" sym field
+  | Cphantom_block { tag; fields; } ->
+    Format.fprintf ppf "[%d: " tag;
+    List.iter (fun field ->
+        Format.fprintf ppf "%a; " V.print field)
+      fields;
+    Format.fprintf ppf "]"
+
+let phantom_defining_expr_opt ppf defining_expr =
+  match defining_expr with
+  | None -> Format.pp_print_string ppf "()"
+  | Some defining_expr -> phantom_defining_expr ppf defining_expr
+
 let operation d = function
   | Capply _ty -> "app" ^ Debuginfo.to_string d
   | Cextcall(lbl, _ty, _alloc, _) ->
@@ -147,6 +170,25 @@ let rec expr ppf = function
      fprintf ppf
       "@[<2>(let@ @[<2>%a@ %a@]@ %a)@]"
       VP.print id expr def sequence body
+  | Cphantom_let(var, def, (Cphantom_let(_, _, _) as body)) ->
+      let print_binding var ppf def =
+        fprintf ppf "@[<2>%a@ %a@]" VP.print var
+          phantom_defining_expr_opt def
+      in
+      let rec in_part ppf = function
+        | Cphantom_let(var, def, body) ->
+            fprintf ppf "@ %a" (print_binding var) def;
+            in_part ppf body
+        | exp -> exp in
+      fprintf ppf "@[<2>(let?@ @[<1>(%a" (print_binding var) def;
+      let exp = in_part ppf body in
+      fprintf ppf ")@]@ %a)@]" sequence exp
+  | Cphantom_let(var, def, body) ->
+    fprintf ppf
+      "@[<2>(let?@ @[<2>%a@ %a@]@ %a)@]"
+      VP.print var
+      phantom_defining_expr_opt def
+      sequence body
   | Cassign(id, exp) ->
       fprintf ppf "@[<2>(assign @[<2>%a@ %a@])@]" V.print id expr exp
   | Ctuple el ->

asmcomp/selectgen.ml

@@ -298,6 +298,7 @@ method is_simple_expr = function
   | Cvar _ -> true
   | Ctuple el -> List.for_all self#is_simple_expr el
   | Clet(_id, arg, body) -> self#is_simple_expr arg && self#is_simple_expr body
+  | Cphantom_let(_var, _defining_expr, body) -> self#is_simple_expr body
   | Csequence(e1, e2) -> self#is_simple_expr e1 && self#is_simple_expr e2
   | Cop(op, args, _) ->
       begin match op with
@@ -333,6 +334,7 @@ method effects_of exp =
   | Ctuple el -> EC.join_list_map el self#effects_of
   | Clet (_id, arg, body) ->
     EC.join (self#effects_of arg) (self#effects_of body)
+  | Cphantom_let (_var, _defining_expr, body) -> self#effects_of body
   | Csequence (e1, e2) ->
     EC.join (self#effects_of e1) (self#effects_of e2)
   | Cifthenelse (cond, ifso, ifnot) ->
@@ -670,6 +672,8 @@ method emit_expr (env:environment) exp =
         None -> None
       | Some r1 -> self#emit_expr (self#bind_let env v r1) e2
       end
+  | Cphantom_let (_var, _defining_expr, body) ->
+      self#emit_expr env body
   | Cassign(v, e1) ->
       let rv =
         try
@@ -1037,6 +1041,8 @@ method emit_tail (env:environment) exp =
         None -> ()
       | Some r1 -> self#emit_tail (self#bind_let env v r1) e2
       end
+  | Cphantom_let (_var, _defining_expr, body) ->
+      self#emit_tail env body
   | Cop((Capply ty) as op, args, dbg) ->
       begin match self#emit_parts_list env args with
         None -> ()