[m-dev.] Re: diff: fix bug with trail tickets and --trace shallow

[Fergus Henderson]

On 11-Dec-2000, Fergus Henderson <fjh at cs.mu.oz.au> wrote:
> Estimated hours taken: 2
> 
> compiler/code_gen.m:
> 	Fix a bug reported by Warwick Harvey: the code that we
> 	generated for procedures compiled with `--trace shallow'
> 	was allocating ticket counters conditionally
> 	(iff MR_trace_from_full was true on entry),
> 	but was deallocating them unconditionally.
> 	The fix was to only deallocate them if they were allocated.

Estimated hours taken: 0.5

compiler/code_gen.m:
	Fix a bug in my previous change: it was generating duplicate label names.

Workspace: /home/pgrad/fjh/ws/hg3
Index: compiler/code_gen.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/code_gen.m,v
retrieving revision 1.90
diff -u -d -r1.90 code_gen.m
--- compiler/code_gen.m	2000/12/11 10:42:38	1.90
+++ compiler/code_gen.m	2000/12/13 00:09:22
@@ -873,24 +873,41 @@
 				% only if it was allocated, i.e. only if
 				% MR_trace_from_full was true on entry.
 				%
+				% Note that to avoid duplicating label names,
+				% we need to generate two different copies
+				% of this with different labels; this is
+				% needed for semidet code, which will get one
+				% copy in the success epilogue and one copy
+				% in the failure epilogue
+				%
 				{ FromFullSlotLval =
 					llds__stack_slot_num_to_lval(
 						CodeModel, FromFullSlot) },
 				code_info__get_next_label(SkipLabel),
+				code_info__get_next_label(SkipLabelCopy),
 				{ PruneTraceTicketCode = node([
 					if_val(unop(not,
 						lval(FromFullSlotLval)),
 						label(SkipLabel)) - "",
 					prune_ticket - "prune retry ticket",
 					label(SkipLabel) - ""
+				]) },
+				{ PruneTraceTicketCodeCopy = node([
+					if_val(unop(not,
+						lval(FromFullSlotLval)),
+						label(SkipLabelCopy)) - "",
+					prune_ticket - "prune retry ticket",
+					label(SkipLabelCopy) - ""
 				]) }
 			;
 				{ PruneTraceTicketCode = node([
 					prune_ticket - "prune retry ticket"
-				]) }
+				]) },
+				{ PruneTraceTicketCodeCopy = PruneTraceTicketCode }
 			)
 		;
-			{ PruneTraceTicketCode = empty }
+			{ PruneTraceTicketCode = empty },
+			{ PruneTraceTicketCodeCopy = empty }
 		),
 
 		{ RestoreDeallocCode =
@@ -898,6 +915,11 @@
 			tree(PruneTraceTicketCode,
 			     DeallocCode))
 		},
+		{ RestoreDeallocCodeCopy =
+			tree(RestoreSuccipCode,
+			tree(PruneTraceTicketCodeCopy,
+			     DeallocCode))
+		},
 
 		code_info__get_maybe_trace_info(MaybeTraceInfo),
 		( { MaybeTraceInfo = yes(TraceInfo) } ->
@@ -941,7 +963,7 @@
 			]) },
 			{ AllSuccessCode =
 				tree(TraceExitCode,
-				tree(RestoreDeallocCode,
+				tree(RestoreDeallocCodeCopy,
 				     SuccessCode))
 			}
 		;
@@ -954,7 +976,7 @@
 			]) },
 			{ AllSuccessCode =
 				tree(TraceExitCode,
-				tree(RestoreDeallocCode,
+				tree(RestoreDeallocCodeCopy,
 				     SuccessCode))
 			}
 		;
-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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