[m-rev.] diff: simplifying special ites

[Zoltan Somogyi]

compiler/simplify.m:
	Move the code for handling a special case in the simplification
	of if-then-elses to the predicate that handles all other special cases
	for ites.

Zoltan.

cvs diff: Diffing .
Index: simplify.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/simplify.m,v
retrieving revision 1.280
diff -u -b -r1.280 simplify.m
--- simplify.m	14 Jun 2012 07:03:56 -0000	1.280
+++ simplify.m	18 Jun 2012 06:54:25 -0000
@@ -1072,8 +1072,8 @@
         Goals = [_, _ | _],
 
         % Conjunctions that cannot produce solutions may nevertheless contain
-        % nondet and multi goals. If this happens, the conjunction is put
-        % inside a scope to appease the code generator.
+        % nondet and multi goals. If this happens, we put the conjunction
+        % inside a commit scope to appease the code generator.
 
         Detism = goal_info_get_determinism(GoalInfo0),
         (
@@ -1485,10 +1485,10 @@
     determinism_components(CondDetism0, CondCanFail0, CondSolns0),
     (
         CondCanFail0 = cannot_fail,
-        goal_to_conj_list(Cond0, CondList),
-        goal_to_conj_list(Then0, ThenList),
-        list.append(CondList, ThenList, List),
-        simplify_goal(hlds_goal(conj(plain_conj, List), GoalInfo0),
+        goal_to_conj_list(Cond0, CondGoals),
+        goal_to_conj_list(Then0, ThenGoals),
+        Goals = CondGoals ++ ThenGoals,
+        simplify_goal(hlds_goal(conj(plain_conj, Goals), GoalInfo0),
             hlds_goal(GoalExpr, GoalInfo), !Info),
         simplify_info_get_inside_duplicated_for_switch(!.Info,
             InsideDuplForSwitch),
@@ -1582,9 +1582,20 @@
             ; CondSolns0 = at_most_many
             ; CondSolns0 = at_most_many_cc
             ),
+            ( Else0 = hlds_goal(disj([]), _) ->
+                % (Cond -> Then ; fail) is equivalent to (Cond, Then)
+                goal_to_conj_list(Cond0, CondGoals),
+                goal_to_conj_list(Then0, ThenGoals),
+                Goals = CondGoals ++ ThenGoals,
+                simplify_goal(hlds_goal(conj(plain_conj, Goals), GoalInfo0),
+                    hlds_goal(GoalExpr, GoalInfo), !Info),
+                simplify_info_set_requantify(!Info),
+                simplify_info_set_rerun_det(!Info)
+            ;
             simplify_goal_ordinary_ite(Vars, Cond0, Then0, Else0, GoalExpr,
                 GoalInfo0, GoalInfo, !Info)
         )
+        )
     ).
 
 :- pred simplify_goal_ordinary_ite(list(prog_var)::in,
@@ -1594,16 +1605,6 @@
 
 simplify_goal_ordinary_ite(Vars, Cond0, Then0, Else0, GoalExpr,
         GoalInfo0, GoalInfo, !Info) :-
-    ( Else0 = hlds_goal(disj([]), _) ->
-        % (A -> C ; fail) is equivalent to (A, C)
-        goal_to_conj_list(Cond0, CondList),
-        goal_to_conj_list(Then0, ThenList),
-        list.append(CondList, ThenList, List),
-        simplify_goal(hlds_goal(conj(plain_conj, List), GoalInfo0),
-            hlds_goal(GoalExpr, GoalInfo), !Info),
-        simplify_info_set_requantify(!Info),
-        simplify_info_set_rerun_det(!Info)
-    ;
         % Recursively simplify the sub-goals, and rebuild the resulting
         % if-then-else.
 
@@ -1619,8 +1620,8 @@
         CondDelta = goal_info_get_instmap_delta(CondInfo),
         Then = hlds_goal(_, ThenInfo),
         ThenDelta = goal_info_get_instmap_delta(ThenInfo),
-        instmap_delta_apply_instmap_delta(CondDelta, ThenDelta,
-            test_size, CondThenDelta),
+    instmap_delta_apply_instmap_delta(CondDelta, ThenDelta, test_size,
+        CondThenDelta),
         Else = hlds_goal(_, ElseInfo),
         ElseDelta = goal_info_get_instmap_delta(ElseInfo),
         NonLocals = goal_info_get_nonlocals(GoalInfo0),
@@ -1651,8 +1652,7 @@
             )
         ->
             simplify_info_undo_goal_updates(Info0, !Info),
-            simplify_goal_expr(IfThenElse, GoalExpr, GoalInfo1, GoalInfo,
-                !Info)
+        simplify_goal_expr(IfThenElse, GoalExpr, GoalInfo1, GoalInfo, !Info)
         ;
             simplify_info_get_module_info(!.Info, ModuleInfo),
             warn_switch_for_ite_cond(ModuleInfo, VarTypes, Cond,
@@ -1683,18 +1683,17 @@
                 CanSwitch = cond_cannot_switch
             ),
             (
-                % If-then-elses that are det or semidet may nevertheless
-                % contain nondet or multi conditions. If this happens,
-                % the if-then-else must be put inside a `scope' to appease
-                % the code generator. (Both the MLDS and LLDS back-ends
-                % rely on this.)
+            % If-then-elses that are det or semidet may nevertheless contain
+            % nondet or multi conditions. If this happens, the if-then-else
+            % must be put inside a `scope' to appease the code generator.
+            % (Both the MLDS and LLDS back-ends rely on this.)
 
                 simplify_do_once(!.Info),
                 CondSolns = at_most_many,
                 IfThenElseNumSolns \= at_most_many
             ->
-                determinism_components(InnerDetism,
-                    IfThenElseCanFail, at_most_many),
+            determinism_components(InnerDetism, IfThenElseCanFail,
+                at_most_many),
                 goal_info_set_determinism(InnerDetism, GoalInfo1, InnerInfo),
                 GoalExpr = scope(commit(dont_force_pruning),
                     hlds_goal(IfThenElse, InnerInfo))
@@ -1702,7 +1701,6 @@
                 GoalExpr = IfThenElse
             ),
             GoalInfo = GoalInfo1
-        )
     ).
 
 :- type cond_can_switch
@@ -3051,8 +3049,8 @@
             Call = hlds_goal(Call1, CallGoalInfo1)
         )
     ),
-    list.append(ExtraGoals, [Call], ConjList),
-    conj_list_to_goal(ConjList, GoalInfo0, Goal).
+    Conjuncts = ExtraGoals ++ [Call],
+    conj_list_to_goal(Conjuncts, GoalInfo0, Goal).
 
 :- pred call_generic_unify(prog_var::in, prog_var::in,  prog_var::in,
     module_info::in, simplify_info::in, unify_context::in,
@@ -3074,7 +3072,7 @@
 call_specific_unify(TypeCtor, TypeInfoVars, XVar, YVar, ProcId, ModuleInfo,
         Context, GoalInfo0, CallExpr, CallGoalInfo) :-
     % Create the new call goal.
-    list.append(TypeInfoVars, [XVar, YVar], ArgVars),
+    ArgVars = TypeInfoVars ++ [XVar, YVar],
     module_info_get_special_pred_map(ModuleInfo, SpecialPredMap),
     map.lookup(SpecialPredMap, spec_pred_unify - TypeCtor, PredId),
     module_info_pred_info(ModuleInfo, PredId, PredInfo),
@@ -3320,7 +3318,7 @@
     Info0 = !.Info,
     % Flatten conjunctions.
     ( Goal0 = hlds_goal(conj(plain_conj, SubGoals), _) ->
-        list.append(SubGoals, Goals0, Goals1),
+        Goals1 = SubGoals ++ Goals0,
         simplify_conj(Goals1, !.RevGoals, Goals, ConjInfo, !Info)
     ;
         simplify_goal(Goal0, Goal1, !Info),
@@ -3329,7 +3327,7 @@
             Goal1 = hlds_goal(conj(plain_conj, SubGoals1), _)
         ->
             simplify_info_undo_goal_updates(Info0, !Info),
-            list.append(SubGoals1, Goals0, Goals1),
+            Goals1 = SubGoals1 ++ Goals0,
             simplify_conj(Goals1, !.RevGoals, Goals, ConjInfo, !Info)
         ;
             % Delete unreachable goals.
@@ -3377,7 +3375,7 @@
 conjoin_goal_and_rev_goal_list(Goal, RevGoals0, RevGoals) :-
     ( Goal = hlds_goal(conj(plain_conj, Goals), _) ->
         list.reverse(Goals, Goals1),
-        list.append(Goals1, RevGoals0, RevGoals)
+        RevGoals = Goals1 ++ RevGoals0
     ;
         RevGoals = [Goal | RevGoals0]
     ).
cvs diff: Diffing notes
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