Make -f[no-]method-sharing a dynamic flag

We want -Odph to be a dynamic flag and that should imply -fno-method-sharing.
This doesn't add a lot of complexity.

compiler/main/DynFlags.hs

@@ -248,6 +248,7 @@ data DynFlag
    | Opt_DoEtaReduction
    | Opt_CaseMerge
    | Opt_UnboxStrictFields
+   | Opt_MethodSharing
    | Opt_DictsCheap
    | Opt_RewriteRules
    | Opt_Vectorise
@@ -555,6 +556,8 @@ defaultDynFlags =
             Opt_ImplicitPrelude,
             Opt_MonomorphismRestriction,
 
+            Opt_MethodSharing,
+
             Opt_DoAsmMangling,
 
             Opt_GenManifest,
@@ -1271,6 +1274,7 @@ fFlags = [
   ( "do-eta-reduction",                 Opt_DoEtaReduction ),
   ( "case-merge",                       Opt_CaseMerge ),
   ( "unbox-strict-fields",              Opt_UnboxStrictFields ),
+  ( "method-sharing",                   Opt_MethodSharing ),
   ( "dicts-cheap",                      Opt_DictsCheap ),
   ( "excess-precision",                 Opt_ExcessPrecision ),
   ( "asm-mangling",                     Opt_DoAsmMangling ),

compiler/main/StaticFlags.hs

@@ -38,7 +38,6 @@ module StaticFlags (
 	opt_Parallel,
 
 	-- optimisation opts
-	opt_NoMethodSharing, 
 	opt_NoStateHack,
 	opt_SpecInlineJoinPoints,
 	opt_CprOff,
@@ -317,8 +316,6 @@ opt_SpecInlineJoinPoints :: Bool
 opt_SpecInlineJoinPoints	= lookUp  (fsLit "-fspec-inline-join-points")
 opt_NoStateHack :: Bool
 opt_NoStateHack			= lookUp  (fsLit "-fno-state-hack")
-opt_NoMethodSharing :: Bool
-opt_NoMethodSharing		= lookUp  (fsLit "-fno-method-sharing")
 opt_CprOff :: Bool
 opt_CprOff			= lookUp  (fsLit "-fcpr-off")
 	-- Switch off CPR analysis in the new demand analyser

compiler/typecheck/TcExpr.lhs

@@ -785,7 +785,8 @@ instFun orig fun subst tv_theta_prs
 	; doStupidChecks fun ty_theta_prs'
 
 		-- Now do normal instantiation
-	; result <- go True fun ty_theta_prs' 
+        ; method_sharing <- doptM Opt_MethodSharing
+	; result <- go method_sharing True fun ty_theta_prs' 
 	; traceTc (text "instFun result" <+> ppr result)
 	; return result
 	}
@@ -793,24 +794,24 @@ instFun orig fun subst tv_theta_prs
     subst_pr (tvs, theta) 
 	= (substTyVars subst tvs, substTheta subst theta)
 
-    go _ fun [] = do {traceTc (text "go _ fun [] returns" <+> ppr fun) ; return fun }
+    go _ _ fun [] = do {traceTc (text "go _ _ fun [] returns" <+> ppr fun) ; return fun }
 
-    go True (HsVar fun_id) ((tys,theta) : prs)
-	| want_method_inst theta
+    go method_sharing True (HsVar fun_id) ((tys,theta) : prs)
+	| want_method_inst method_sharing theta
 	= do { traceTc (text "go (HsVar fun_id) ((tys,theta) : prs) | want_method_inst theta")
 	     ; meth_id <- newMethodWithGivenTy orig fun_id tys
-	     ; go False (HsVar meth_id) prs }
+	     ; go method_sharing False (HsVar meth_id) prs }
 		-- Go round with 'False' to prevent further use
 		-- of newMethod: see Note [Multiple instantiation]
 
-    go _ fun ((tys, theta) : prs)
+    go method_sharing _ fun ((tys, theta) : prs)
 	= do { co_fn <- instCall orig tys theta
 	     ; traceTc (text "go yields co_fn" <+> ppr co_fn)
-	     ; go False (HsWrap co_fn fun) prs }
+	     ; go method_sharing False (HsWrap co_fn fun) prs }
 
 	-- See Note [No method sharing]
-    want_method_inst theta =  not (null theta)	-- Overloaded
-		   	   && not opt_NoMethodSharing
+    want_method_inst method_sharing theta =  not (null theta)	-- Overloaded
+		   	                  && method_sharing
 \end{code}
 
 Note [Multiple instantiation]

docs/users_guide/flags.xml

@@ -1207,6 +1207,13 @@
 	      <entry><option>-fno-dicts-strict</option></entry>
 	    </row>
 
+	    <row>
+	      <entry><option>-fmethod-sharing</option></entry>
+	      <entry>Share specialisations of overloaded functions (default)</entry>
+	      <entry>dynamic</entry>
+	      <entry><option>-fno-method-sharing</option></entry>
+	    </row>
+
 	    <row>
 	      <entry><option>-fdo-eta-reduction</option></entry>
 	      <entry>Enable eta-reduction. Implied by <option>-O</option>.</entry>
@@ -2303,12 +2310,6 @@
 	      <entry>static</entry>
 	      <entry>-</entry>
 	    </row>
-	    <row>
-	      <entry><option>-fno-method-sharing</option></entry>
-	      <entry>Don't share specialisations of overloaded functions</entry>
-	      <entry>static</entry>
-	      <entry>-</entry>
-	    </row>
 	    <row>
 	      <entry><option>-fhistory-size</option></entry>
 	      <entry>Set simplification history size</entry>