Add -native-pic {false,true} option

Can be used to override a platform-determined default.

See MLton#191

mlton/codegen/amd64-codegen/amd64-allocate-registers.fun

@@ -1,4 +1,4 @@
-(* Copyright (C) 1999-2010 Matthew Fluet.
+(* Copyright (C) 2010,2020 Matthew Fluet.
  * Copyright (C) 1999-2007 Henry Cejtin, Matthew Fluet, Suresh
  *    Jagannathan, and Stephen Weeks.
  * Copyright (C) 1997-2000 NEC Research Institute.
@@ -3824,7 +3824,7 @@ struct
                       assembly = AppendList.empty,
                       registerAllocation = registerAllocation}
                   | (_, NONE, SOME memIndex) (* label + index => use lea if PIC *)
-                  => if !Control.positionIndependent = false
+                  => if not (!Control.Native.pic)
                         then {disp = SOME disp,
                               register = NONE,
                               assembly = AppendList.empty,

mlton/codegen/amd64-codegen/amd64-generate-transfers.fun

@@ -1550,7 +1550,7 @@ struct
                               in
                                 case (symbolScope,
                                       !Control.Target.os, 
-                                      !Control.positionIndependent) of
+                                      !Control.Native.pic) of
                                    (* Private functions can be easily reached
                                     * with a direct (rip-relative) call.
                                     *)

mlton/codegen/amd64-codegen/amd64-translate.fun

@@ -186,7 +186,7 @@ struct
                in
                   case (symbolScope,
                         !Control.Target.os,
-                        !Control.positionIndependent) of
+                        !Control.Native.pic) of
                    (* As long as the symbol is private (this means it is not
                     * exported to code outside this text segment), then
                     * RIP-relative addressing works on every OS/format.

mlton/codegen/x86-codegen/x86-allocate-registers.fun

@@ -1,4 +1,4 @@
-(* Copyright (C) 2010 Matthew Fluet.
+(* Copyright (C) 2010,2020 Matthew Fluet.
  * Copyright (C) 1999-2007 Henry Cejtin, Matthew Fluet, Suresh
  *    Jagannathan, and Stephen Weeks.
  * Copyright (C) 1997-2000 NEC Research Institute.
@@ -38,7 +38,7 @@ struct
          fun mungeLabelDarwin l =
            Label.fromString (Label.toString l ^ "-MLtonLocalBaseSymbol")
       in
-        case (!Control.Target.os, !Control.positionIndependent) of
+        case (!Control.Target.os, !Control.Native.pic) of
             (* Only darwin and ELF might be using PIC *)
             (Darwin, true) => (mungeLabelDarwin, SOME Register.esp)
           | (_, true) => (mungeLabelELF, SOME Register.ebx)

mlton/codegen/x86-codegen/x86-generate-transfers.fun

@@ -1393,7 +1393,7 @@ struct
                               in
                                 case (symbolScope,
                                       !Control.Target.os,
-                                      !Control.positionIndependent) of
+                                      !Control.Native.pic) of
                                    (* Private functions can be easily reached
                                     * with a direct (eip-relative) call.
                                     *)

mlton/codegen/x86-codegen/x86-translate.fun

@@ -202,7 +202,7 @@ struct
                in
                   case (symbolScope,
                         !Control.Target.os,
-                        !Control.positionIndependent) of
+                        !Control.Native.pic) of
                    (* Even private PIC symbols on darwin need indirection. *)
                      (Private, Darwin, true) => indirect ()
                    (* As long as the symbol is private (thus it is not

mlton/control/control-flags.sig

@@ -362,6 +362,9 @@ signature CONTROL_FLAGS =
 
             (* whether or not to split assembly file in native codegen *)
             val split: int option ref
+
+            (* whether or not to use position-independent code in native codegen *)
+            val pic: bool ref
          end
 
       val numExports: int ref
@@ -379,8 +382,6 @@ signature CONTROL_FLAGS =
             val setAll: string -> unit Result.t
          end
 
-      val positionIndependent : bool ref
-
       (* Only duplicate big functions when
        * (size - small) * (number of occurrences - 1) <= product
        *)

mlton/control/control-flags.sml

@@ -1269,6 +1269,10 @@ structure Native =
       val split = control {name = "native split",
                            default = SOME 20000,
                            toString = Option.toString Int.toString}
+
+      val pic = control {name = "native pic",
+                         default = false,
+                         toString = Bool.toString}
    end
 
 val numExports: int ref = ref 0
@@ -1344,8 +1348,6 @@ val polyvariance =
                              ("product", Int.layout product)])
              p)}
 
-val positionIndependent = ref false
-
 val preferAbsPaths = control {name = "prefer abs paths",
                               default = false,
                               toString = Bool.toString}

mlton/main/main.fun

@@ -76,6 +76,7 @@ val explicitAlign: Control.align option ref = ref NONE
 val explicitChunkify: Control.Chunkify.t option ref = ref NONE
 datatype explicitCodegen = Native | Explicit of Control.Codegen.t
 val explicitCodegen: explicitCodegen option ref = ref NONE
+val explicitNativePIC: bool option ref = ref NONE
 val keepGenerated = ref false
 val keepO = ref false
 val output: string option ref = ref NONE
@@ -650,6 +651,8 @@ fun makeOptions {usage} =
         boolRef Native.moveHoist),
        (Expert, "native-optimize", " <n>", "level of optimizations",
         intRef Native.optimize),
+       (Expert, "native-pic", " {false|true}", "generate position-independent code",
+        Bool (fn b => explicitNativePIC := SOME b)),
        (Expert, "native-split", " <n>", "split assembly files at ~n lines",
         Int (fn i => Native.split := SOME i)),
        (Expert, "native-shuffle", " {true|false}",
@@ -1009,7 +1012,11 @@ fun commandLine (args: string list): unit =
           | (_, _, Library) => true
           | (_, _, LibArchive) => true
           | _ => false
-      val () = Control.positionIndependent := positionIndependent
+
+      val () =
+         Native.pic := (case !explicitNativePIC of
+                           NONE => positionIndependent
+                         | SOME b => b)
 
       val stop = !stop