Merge pull request #448 from mshinwell/sensible_num_args

GPR#448: Add Proc.max_arguments_without_passing_on_stack

asmcomp/amd64/proc.ml

@@ -76,6 +76,8 @@ let masm =
      Linux's dynamic loader also destroys r10.
 *)
 
+let max_arguments_for_tailcalls = 10
+
 let int_reg_name =
   match Config.ccomp_type with
   | "msvc" ->

asmcomp/arm/proc.ml

@@ -180,6 +180,8 @@ let not_supported ofs = fatal_error "Proc.loc_results: cannot call"
      remaining args on stack.
    Return values in r0...r7 or d0...d15. *)
 
+let max_arguments_for_tailcalls = 8
+
 let single_regs arg = Array.map (fun arg -> [| arg |]) arg
 let ensure_single_regs res =
   Array.map (function

asmcomp/arm64/proc.ml

@@ -140,6 +140,8 @@ let not_supported ofs = fatal_error "Proc.loc_results: cannot call"
      remaining args on stack.
    Return values in r0...r15 or d0...d15. *)
 
+let max_arguments_for_tailcalls = 16
+
 let loc_arguments arg =
   calling_conventions 0 15 100 115 outgoing arg
 let loc_parameters arg =

asmcomp/i386/proc.ml

@@ -139,6 +139,9 @@ let incoming ofs = Incoming ofs
 let outgoing ofs = Outgoing ofs
 let not_supported ofs = fatal_error "Proc.loc_results: cannot call"
 
+(* Six arguments in integer registers plus eight in global memory. *)
+let max_arguments_for_tailcalls = 14
+
 let loc_arguments arg =
   calling_conventions 0 5 100 99 outgoing arg
 let loc_parameters arg =

asmcomp/power/proc.ml

@@ -174,6 +174,8 @@ let ensure_single_regs res =
       | _ -> failwith "Proc.ensure_single_regs")
     res
 
+let max_arguments_for_tailcalls = 8
+
 let loc_arguments arg =
   let (loc, ofs) =
     calling_conventions 0 7 100 112 outgoing 0 false (single_regs arg)

asmcomp/proc.mli

@@ -37,6 +37,14 @@ val loc_external_arguments: Reg.t array array -> Reg.t array array * int
 val loc_external_results: Reg.t array -> Reg.t array
 val loc_exn_bucket: Reg.t
 
+(* The maximum number of arguments of an OCaml to OCaml function call for
+   which it is guaranteed there will be no arguments passed on the stack.
+   (Above this limit, tail call optimization may be disabled.)
+   N.B. The values for this parameter in the backends currently assume
+   that no unboxed floats are passed using the OCaml calling conventions.
+*)
+val max_arguments_for_tailcalls : int
+
 (* Maximal register pressures for pre-spilling *)
 val safe_register_pressure: Mach.operation -> int
 val max_register_pressure: Mach.operation -> int array

asmcomp/s390x/proc.ml

@@ -125,6 +125,8 @@ let incoming ofs = Incoming ofs
 let outgoing ofs = Outgoing ofs
 let not_supported ofs = fatal_error "Proc.loc_results: cannot call"
 
+let max_arguments_for_tailcalls = 5
+
 let loc_arguments arg =
   calling_conventions 0 4 100 103 outgoing 0 arg
 let loc_parameters arg =

asmcomp/sparc/proc.ml

@@ -133,6 +133,8 @@ let incoming ofs = Incoming ofs
 let outgoing ofs = Outgoing ofs
 let not_supported ofs = fatal_error "Proc.loc_results: cannot call"
 
+let max_arguments_for_tailcalls = 10
+
 let loc_arguments arg =
   calling_conventions 6 15 100 105 outgoing arg
 let loc_parameters arg =

driver/optmain.ml

@@ -26,9 +26,9 @@ module Backend = struct
   let size_int = Arch.size_int
   let big_endian = Arch.big_endian
 
-  (* CR mshinwell: this needs tying through to [Proc], although it may
-     necessitate the introduction of a new field in that module. *)
-  let max_sensible_number_of_arguments = 9
+  let max_sensible_number_of_arguments =
+    (* The "-1" is to allow for a potential closure environment parameter. *)
+    Proc.max_arguments_for_tailcalls - 1
 end
 let backend = (module Backend : Backend_intf.S)