[m-dev.] for review: a proper fix for contexts at exception events

[Zoltan Somogyi]

For review by Fergus or Tyson.

This change is being bootchecked in ~zs/mer/ws6 on ender. If that succeeds,
Fergus may wish to commit this before the nightly checks tonight.

Estimated hours taken: 4

Fix the problem with contexts at exception ports in a way that (unlike Fergus's
fix) does not slow down the speed-critical code path inside the debugger.

compiler/stack_layout.m:
	When generating label layouts for return labels, give the two fields
	of the layout structure that correspond to arguments of the old
	four-argument MR_trace() values that are appropriate for use in
	exception events, i.e. port is exception and goal path is empty.

compiler/llds.m:
compiler/llds_out.m:
	Add exception to the trace port type, since the compiler now refers
	to it.

runtime/mercury_stack_layout.h:
trace/mercury_trace.c:
	Undo Fergus's change.

library/exception.m:
	Undo Fergus's change, and my change previous to that. Pass the
	return layout to MR_trace unchanged, after checking that it indeed
	specifies an exception port.

Zoltan.

cvs diff: Diffing .
cvs diff: Diffing bindist
cvs diff: Diffing boehm_gc
cvs diff: Diffing boehm_gc/Mac_files
cvs diff: Diffing boehm_gc/cord
cvs diff: Diffing boehm_gc/cord/private
cvs diff: Diffing boehm_gc/include
cvs diff: Diffing boehm_gc/include/private
cvs diff: Diffing browser
cvs diff: Diffing bytecode
cvs diff: Diffing compiler
Index: compiler/llds.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/llds.m,v
retrieving revision 1.254
diff -u -b -r1.254 llds.m
--- compiler/llds.m	1999/12/14 04:52:43	1.254
+++ compiler/llds.m	1999/12/16 06:23:56
@@ -512,16 +512,15 @@
 	;	gc
 	.
 
-	% The kinds of ports for which the code we generate will
-	% call MR_trace. The exception port is not on this list, because for
-	% that port the code that calls MR_trace is not in compiler-generated
-	% code, but in the runtime system. (The same comment applies to the
-	% type `external_trace_port' in trace.m.)
+	% The kinds of events with which MR_trace may be called, either
+	% by compiler-generated code, or by code in the standard library
+	% referring to compiler-generated data structures.
 :- type trace_port
 	--->	call
 	;	exit
 	;	fail
 	;	redo
+	;	exception
 	;	ite_cond
 	;	ite_then
 	;	ite_else
Index: compiler/llds_out.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/llds_out.m,v
retrieving revision 1.132
diff -u -b -r1.132 llds_out.m
--- compiler/llds_out.m	1999/12/14 04:52:45	1.132
+++ compiler/llds_out.m	1999/12/16 06:24:48
@@ -837,6 +837,7 @@
 llds_out__trace_port_to_string(exit, "MR_PORT_EXIT").
 llds_out__trace_port_to_string(redo, "MR_PORT_REDO").
 llds_out__trace_port_to_string(fail, "MR_PORT_FAIL").
+llds_out__trace_port_to_string(exception, "MR_PORT_EXCEPTION").
 llds_out__trace_port_to_string(ite_cond, "MR_PORT_COND").
 llds_out__trace_port_to_string(ite_then, "MR_PORT_THEN").
 llds_out__trace_port_to_string(ite_else, "MR_PORT_ELSE").
@@ -852,7 +853,8 @@
 llds_out__trace_port_to_num(exit, 1).
 llds_out__trace_port_to_num(redo, 2).
 llds_out__trace_port_to_num(fail, 3).
-llds_out__trace_port_to_num(ite_cond, 5).	% exception is 4
+llds_out__trace_port_to_num(exception, 4).
+llds_out__trace_port_to_num(ite_cond, 5).
 llds_out__trace_port_to_num(ite_then, 6).
 llds_out__trace_port_to_num(ite_else, 7).
 llds_out__trace_port_to_num(neg_enter,   8).
Index: compiler/stack_layout.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/stack_layout.m,v
retrieving revision 1.41
diff -u -b -r1.41 stack_layout.m
--- compiler/stack_layout.m	1999/12/14 04:52:58	1.41
+++ compiler/stack_layout.m	1999/12/16 07:31:22
@@ -838,19 +838,11 @@
 	(
 		{ Trace = no },
 		{ set__init(TraceLiveVarSet) },
-		{ map__init(TraceTypeVarMap) },
-		{ TraceRvals = [yes(const(int_const(-1))),
-				yes(const(int_const(-1)))] }
+		{ map__init(TraceTypeVarMap) }
 	;
-		{ Trace = yes(trace_port_layout_info(_, Port, Path,
-			TraceLayout)) },
+		{ Trace = yes(trace_port_layout_info(_, _, _, TraceLayout)) },
 		{ TraceLayout = layout_label_info(TraceLiveVarSet,
-			TraceTypeVarMap) },
-		{ llds_out__trace_port_to_num(Port, PortNum) },
-		{ trace__path_to_string(Path, PathStr) },
-		stack_layout__lookup_string_in_table(PathStr, PathNum),
-		{ TraceRvals = [yes(const(int_const(PortNum))),
-				yes(const(int_const(PathNum)))] }
+			TraceTypeVarMap) }
 	),
 	{ TraceArgTypes = [2 - yes(int_least16)] },
 	{
@@ -862,6 +854,31 @@
 		ResumeLayout = layout_label_info(ResumeLiveVarSet,
 			ResumeTypeVarMap)
 	},
+	(
+		{ Trace = yes(trace_port_layout_info(_, Port, Path, _)) },
+		{ Return = no },
+		{ llds_out__trace_port_to_num(Port, PortNum) },
+		{ trace__path_to_string(Path, PathStr) },
+		stack_layout__lookup_string_in_table(PathStr, PathNum)
+	;
+		{ Trace = no },
+		{ Return = yes(_) },
+			% We only ever use the port and path fields of these
+			% layout structures when we process exception events.
+		{ llds_out__trace_port_to_num(exception, PortNum) },
+		{ PathNum = 0 }
+	;
+		{ Trace = no },
+		{ Return = no },
+		{ PortNum = -1 },
+		{ PathNum = -1 }
+	;
+		{ Trace = yes(_) },
+		{ Return = yes(_) },
+		{ error("label has both trace and return layout info") }
+	),
+	{ TraceRvals = [yes(const(int_const(PortNum))),
+			yes(const(int_const(PathNum)))] },
 	stack_layout__get_agc_stack_layout(AgcStackLayout),
 	{
 		Return = no,
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Index: library/exception.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/exception.m,v
retrieving revision 1.9
diff -u -b -r1.9 exception.m
--- library/exception.m	1999/12/15 19:15:13	1.9
+++ library/exception.m	1999/12/16 07:41:33
@@ -506,7 +506,6 @@
 		Code 				*MR_jumpaddr;
 		MR_Stack_Walk_Step_Result	result;
 		const char			*problem;
-		MR_Exception_Layout		exception_layout;
 
 		/*
 		** check if we've reached a frame with an exception handler
@@ -520,24 +519,13 @@
 		}
 
 		/*
-		** Note: this is a structure assignment, but we must avoid
-		** using gcc's builtin memcpy, since that causes errors due
-		** to our use of a reserved register.
-		**
-		** Note also that the goal path is an index into the
-		** module-wide string table; the string at index 0 will
-		** always be the empty string.
-		*/
-		MR_memcpy(&exception_layout.MR_el_layout, return_label_layout,
-			sizeof(exception_layout));
-		exception_layout.MR_el_layout.MR_sll_port = MR_PORT_EXCEPTION;
-		exception_layout.MR_el_layout.MR_sll_goal_path = 0;
-		exception_layout.MR_el_return_layout = return_label_layout;
-
-		/*
 		** invoke MR_trace() to trace the exception
 		*/
-		MR_jumpaddr = MR_trace(&exception_layout.MR_el_layout);
+		if (return_label_layout->MR_sll_port != MR_PORT_EXCEPTION) {
+			fatal_error(""return layout port is not exception"");
+		}
+
+		MR_jumpaddr = MR_trace(return_label_layout);
 		if (MR_jumpaddr != NULL) {
 			return MR_jumpaddr;
 		}
cvs diff: Diffing profiler
cvs diff: Diffing runtime
Index: runtime/mercury_stack_layout.h
===================================================================
RCS file: /home/mercury1/repository/mercury/runtime/mercury_stack_layout.h,v
retrieving revision 1.34
diff -u -b -r1.34 mercury_stack_layout.h
--- runtime/mercury_stack_layout.h	1999/12/15 19:15:20	1.34
+++ runtime/mercury_stack_layout.h	1999/12/16 05:16:45
@@ -555,20 +555,6 @@
 
 /*-------------------------------------------------------------------------*/
 /*
-** Definitions for MR_Exception_Layout
-**
-** The first field will be a copy of the stack layout for the return label,
-** with the port changed to `MR_PORT_EXCEPTION', and with an empty goal path.
-** The second field will hold the address of the original return label layout.
-*/
-
-typedef	struct MR_Exception_Layout_Struct {
-	MR_Stack_Layout_Label	MR_el_layout;
-	MR_Stack_Layout_Label	*MR_el_return_layout;
-} MR_Exception_Layout;
-
-/*-------------------------------------------------------------------------*/
-/*
 ** Definitions for MR_Module_Layout
 **
 ** The layout struct for a module contains three main components.
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cvs diff: Diffing trace
Index: trace/mercury_trace.c
===================================================================
RCS file: /home/mercury1/repository/mercury/trace/mercury_trace.c,v
retrieving revision 1.18
diff -u -b -r1.18 mercury_trace.c
--- trace/mercury_trace.c	1999/12/15 19:15:25	1.18
+++ trace/mercury_trace.c	1999/12/16 07:21:57
@@ -216,20 +216,6 @@
 		*/
 
 		port = (MR_Trace_Port) layout->MR_sll_port;
-		if (port == MR_PORT_EXCEPTION) {
-			/*
-			** `layout' has the correct values, but the wrong
-			** address -- its address won't be in the module
-			** layout table, so MR_event_matches_spy_point()
-			** won't find it.  Now that we've already
-			** extracted the port, we can use the return
-			** layout, which does have the correct address
-			** (but the wrong port and path; the path is
-			** not used here).
-			*/
-			layout = ((const MR_Exception_Layout *) layout)
-				->MR_el_return_layout;
-		}
 		match = MR_event_matches_spy_point(layout, port, &action);
 		if (! match) {
 			if (MR_trace_ctrl.MR_trace_print_level ==
@@ -279,25 +265,9 @@
 	event_info.MR_call_seqno = seqno;
 	event_info.MR_call_depth = depth;
 	event_info.MR_trace_port = port;
-
+	event_info.MR_event_sll = layout;
 	event_info.MR_event_path = layout->MR_sll_entry->MR_sle_module_layout
 			->MR_ml_string_table + layout->MR_sll_goal_path;
-
-	if (port == MR_PORT_EXCEPTION) {
-		/*
-		** `layout' has the correct values, but the
-		** wrong address -- its address won't be in the
-		** module layout table, so MR_find_context() etc.
-		** won't find it.  Now that we've already
-		** extracted the port and path, we can use the return
-		** layout, which does have the correct address
-		** (but the wrong port and path).
-		*/
-		layout = ((const MR_Exception_Layout *) layout)
-			->MR_el_return_layout;
-	}
-
-	event_info.MR_event_sll = layout;
 
 	max_r_num = layout->MR_sll_entry->MR_sle_max_r_num;
 	if (max_r_num + MR_NUM_SPECIAL_REG > MR_MAX_SPECIAL_REG_MR) {
cvs diff: Diffing trial
cvs diff: Diffing util
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