Fix a long-known undocumented bug in which preds for which

code_gen.{nl,pp}: Fix a long-known undocumented bug in which preds for which the main conj has inst 'unreachable' aborted. Before generating a negated goal, save live variables onto the stack so we can find them again later. ite_gen.nl: Before generating the condition of an if-then-else, save the live variables onto the stack so that we can find them in the else clause. live_vars.nl: Add interference for the cases where live vars are saved before negations and ite conditions.
2025-12-18 23:35:25 +00:00 · 1995-02-12 00:56:42 +00:00
parent fc52ecb56a
commit c48b5f6fcf
3 changed files with 51 additions and 14 deletions
--- a/compiler/code_gen.pp
+++ b/compiler/code_gen.pp
@@ -528,11 +528,18 @@ code_gen__generate_det_prolog(EntryCode, SUsed) -->
 :- mode code_gen__generate_det_epilog(out, in, out) is det.

 code_gen__generate_det_epilog(ExitCode) -->
+	code_info__get_instmap(Instmap),
 	code_info__get_arginfo(ArgModes),
 	code_info__get_headvars(HeadVars),
+	{ assoc_list__from_corresponding_lists(HeadVars, ArgModes, Args)},
+	(
+		{ Instmap = unreachable }
+	->
+		{ CodeA = empty }
+	;
+		code_info__setup_call(Args, HeadVars, callee, CodeA)
+	),
 	code_info__get_succip_used(Used),
-	{ assoc_list__from_corresponding_lists(HeadVars, ArgModes, Args) },
-	code_info__setup_call(Args, HeadVars, callee, CodeA),
 	code_info__get_total_stackslot_count(NS0),
 	(
 		{ Used = yes }
@@ -620,11 +627,18 @@ code_gen__generate_semi_prolog(EntryCode, SUsed) -->
 :- mode code_gen__generate_semi_epilog(out, in, out) is det.

 code_gen__generate_semi_epilog(Instr) -->
+	code_info__get_instmap(Instmap),
 	code_info__get_arginfo(ArgModes),
 	code_info__get_headvars(HeadVars),
+	{assoc_list__from_corresponding_lists(HeadVars,ArgModes,Args) },
+	(
+		{ Instmap = unreachable }
+	->
+		{ CodeA = empty }
+	;
+		code_info__setup_call(Args, HeadVars, callee, CodeA)
+	),
 	code_info__get_succip_used(Used),
-	{ assoc_list__from_corresponding_lists(HeadVars, ArgModes, Args) },
-	code_info__setup_call(Args, HeadVars, callee, CodeA),
 	code_info__get_total_stackslot_count(NS0),
 	code_info__failure_cont(FailCont),
 	{ code_gen__output_args(Args, LiveArgs0) },
@@ -731,10 +745,17 @@ code_gen__generate_non_prolog(EntryCode, no) -->
 :- mode code_gen__generate_non_epilog(out, in, out) is det.

 code_gen__generate_non_epilog(Instr) -->
+	code_info__get_instmap(Instmap),
 	code_info__get_arginfo(ArgModes),
 	code_info__get_headvars(HeadVars),
-	{ assoc_list__from_corresponding_lists(HeadVars, ArgModes, Args) },
-	code_info__setup_call(Args, HeadVars, callee, CodeA),
+	{assoc_list__from_corresponding_lists(HeadVars,ArgModes,Args) },
+	(
+		{ Instmap = unreachable }
+	->
+		{ CodeA = empty }
+	;
+		code_info__setup_call(Args, HeadVars, callee, CodeA)
+	),
 	{ code_gen__output_args(Args, LiveArgs) },
 	{ LiveValCode = node([
 		livevals(LiveArgs) - ""
@@ -918,17 +939,19 @@ code_gen__generate_negation(Goal, Code) -->
 	code_info__get_next_label(SuccLab),
 	code_info__push_failure_cont(known(SuccLab)),
 	code_info__maybe_save_hp(Reclaim, SaveHeapCode),
+	code_info__generate_nondet_saves(SaveCode),
 		% The contained goal cannot be nondet, because if it's
 		% mode-correct, it won't have any output vars, and so
 		% it will be semi-det.
 	code_gen__generate_semi_goal(Goal, GoalCode),
+	code_info__remake_with_call_info,
 	code_info__maybe_restore_hp(Reclaim, RestoreHeapCode),
 	code_info__pop_failure_cont,
 	code_info__generate_failure(FailCode),
 	{ SuccessCode = node([
 		label(SuccLab) - "negated goal failed, so proceed"
 	]) },
-	{ Code = tree(tree(SaveHeapCode, GoalCode),
+	{ Code = tree(tree(tree(SaveHeapCode, SaveCode), GoalCode),
 			tree(FailCode, tree(SuccessCode, RestoreHeapCode))) }.

 %---------------------------------------------------------------------------%
--- a/compiler/ite_gen.m
+++ b/compiler/ite_gen.m
@@ -41,17 +41,19 @@ ite_gen__generate_det_ite(CondGoal, ThenGoal, ElseGoal, Instr) -->
 	code_info__maybe_save_hp(ReclaimHeap, HPSaveCode),
 	code_info__get_next_label(ElseLab),
 	code_info__push_failure_cont(known(ElseLab)),
+	code_info__generate_nondet_saves(SaveCode),
 		% Grab the instmap
-	code_info__get_instmap(InstMap),
 		% generate the semi-deterministic test goal
+	code_info__get_instmap(InstMap),
+	code_info__grab_code_info(CodeInfo),
 	code_gen__generate_semi_goal(CondGoal, TestCode),
 	code_info__pop_failure_cont,
-	code_info__grab_code_info(CodeInfo),
 	code_info__maybe_pop_stack(ReclaimHeap, HPPopCode),
 	code_gen__generate_forced_det_goal(ThenGoal, ThenGoalCode),
 		% generate code that executes the then condition
 		% and branches to the end of the if-then-else
 	code_info__slap_code_info(CodeInfo),
+	code_info__remake_with_call_info,
 		% restore the instmap
 	code_info__set_instmap(InstMap),
 	code_info__maybe_restore_hp(ReclaimHeap, HPRestoreCode),
@@ -74,7 +76,7 @@ ite_gen__generate_det_ite(CondGoal, ThenGoal, ElseGoal, Instr) -->
 	) },
 		% generate the then condition
 	{ Instr = tree(
-		tree(HPSaveCode, TestCode),
+		tree(tree(HPSaveCode, SaveCode), TestCode),
 		tree(ThenCode, ElseCode)
 	) },
 	code_info__remake_with_store_map.
@@ -95,18 +97,23 @@ ite_gen__generate_semidet_ite(CondGoal, ThenGoal, ElseGoal, Instr) -->
 	code_info__maybe_save_hp(ReclaimHeap, HPSaveCode),
 	code_info__get_next_label(ElseLab),
 	code_info__push_failure_cont(known(ElseLab)),
+	code_info__generate_nondet_saves(SaveCode),
 		% generate the semi-deterministic test goal
 	code_gen__generate_semi_goal(CondGoal, CondCode),
 	code_info__pop_failure_cont,
+	code_info__get_instmap(InstMap),
 	code_info__grab_code_info(CodeInfo),
 	code_info__maybe_pop_stack(ReclaimHeap, HPPopCode),
 	code_gen__generate_forced_semi_goal(ThenGoal, ThenGoalCode),
 	code_info__slap_code_info(CodeInfo),
+	code_info__remake_with_call_info,
+		% restore the instmap
+	code_info__set_instmap(InstMap),
 	code_info__maybe_restore_hp(ReclaimHeap, HPRestoreCode),
 	code_gen__generate_forced_semi_goal(ElseGoal, ElseGoalCode),
 	code_info__get_next_label(EndLab),
 	{ TestCode = tree(
-		HPSaveCode,
+		tree(HPSaveCode, SaveCode),
 		CondCode
 	) },
 	{ ThenCode = tree(
@@ -147,6 +154,7 @@ ite_gen__generate_nondet_ite(CondGoal, ThenGoal, ElseGoal, Instr) -->
 	code_info__maybe_save_hp(ReclaimHeap, HPSaveCode),
 	code_info__get_next_label(ElseLab),
 	code_info__push_failure_cont(known(ElseLab)),
+	code_info__generate_nondet_saves(SaveCode),
 	{ CondGoal = _ - GoalInfo },
 	{ goal_info_determinism(GoalInfo, CondDeterminism) },
 	{ CondDeterminism = nondeterministic ->
@@ -164,16 +172,20 @@ ite_gen__generate_nondet_ite(CondGoal, ThenGoal, ElseGoal, Instr) -->
 	;
 		{ RestoreRedoipCode = empty }
 	),
+	code_info__get_instmap(InstMap),
 	code_info__grab_code_info(CodeInfo),
 	code_info__maybe_pop_stack(ReclaimHeap, HPPopCode),
 	code_gen__generate_forced_non_goal(ThenGoal, ThenGoalCode),
 	code_info__slap_code_info(CodeInfo),
+	code_info__remake_with_call_info,
+		% restore the instmap
+	code_info__set_instmap(InstMap),
 	code_info__maybe_restore_hp(ReclaimHeap, HPRestoreCode),
 	code_gen__generate_forced_non_goal(ElseGoal, ElseGoalCode),
 	code_info__get_next_label(EndLab),
 	{ TestCode = tree(
 		tree(
-			HPSaveCode,
+			tree(HPSaveCode, SaveCode),
 			ModRedoipCode
 		),
 		CondCode
--- a/compiler/live_vars.m
+++ b/compiler/live_vars.m
@@ -167,7 +167,8 @@ detect_live_vars_in_goal_2(switch(_Var, _Det, Cases0), ExtraLives0, Liveness0,
 detect_live_vars_in_goal_2(if_then_else(_Vars, Cond0, Then0, Else0),
 		ExtraLives0, Liveness0, LiveSets0, Category,
 			ModuleInfo, ExtraLives, Liveness, LiveSets) :-
-	detect_live_vars_in_goal(Cond0, ExtraLives0, Liveness0, LiveSets0,
+	set__insert(LiveSets0, Liveness0, LiveSets0A),
+	detect_live_vars_in_goal(Cond0, ExtraLives0, Liveness0, LiveSets0A,
 			Category,ModuleInfo, ExtraLives1, Liveness1, LiveSets1),
 	detect_live_vars_in_goal(Then0, ExtraLives1, Liveness1, LiveSets1,
 			Category,ModuleInfo,ExtraLives2, _Liveness2, LiveSets2),
@@ -176,7 +177,8 @@ detect_live_vars_in_goal_2(if_then_else(_Vars, Cond0, Then0, Else0),

 detect_live_vars_in_goal_2(not(Goal0), ExtraLives0, Liveness0, LiveSets0,
 		Category, ModuleInfo, ExtraLives, Liveness, LiveSets) :-
-	detect_live_vars_in_goal(Goal0, ExtraLives0, Liveness0, LiveSets0,
+	set__insert(LiveSets0, Liveness0, LiveSets1),
+	detect_live_vars_in_goal(Goal0, ExtraLives0, Liveness0, LiveSets1,
 		Category, ModuleInfo, ExtraLives, Liveness, LiveSets).

 detect_live_vars_in_goal_2(some(_Vs, Goal0), ExtraLives0, Liveness0, LiveSets0,