Add -finfo-table-map which maps info tables to source positions

This new flag embeds a lookup table from the address of an info table
to information about that info table.

The main interface for consulting the map is the `lookupIPE` C function

> InfoProvEnt * lookupIPE(StgInfoTable *info)

The `InfoProvEnt` has the following structure:

> typedef struct InfoProv_{
>     char * table_name;
>     char * closure_desc;
>     char * ty_desc;
>     char * label;
>     char * module;
>     char * srcloc;
> } InfoProv;
>
> typedef struct InfoProvEnt_ {
>     StgInfoTable * info;
>     InfoProv prov;
>     struct InfoProvEnt_ *link;
> } InfoProvEnt;

The source positions are approximated in a similar way to the source
positions for DWARF debugging information. They are only approximate but
in our experience provide a good enough hint about where the problem
might be. It is therefore recommended to use this flag in conjunction
with `-g<n>` for more accurate locations.

The lookup table is also emitted into the eventlog when it is available
as it is intended to be used with the `-hi` profiling mode.

Using this flag will significantly increase the size of the resulting
object file but only by a factor of 2-3x in our experience.

1 files changed, 9 insertions, 0 deletions

diff --git a/rts/Trace.h b/rts/Trace.h
index 08b42fe9bd..f9d677d063 100644
--- a/rts/Trace.h
+++ b/rts/Trace.h
@@ -319,6 +319,14 @@ void traceConcSweepEnd(void);
 void traceConcUpdRemSetFlush(Capability *cap);
 void traceNonmovingHeapCensus(uint32_t log_blk_size,
                               const struct NonmovingAllocCensus *census);
+
+void traceIPE(StgInfoTable *info,
+               const char *table_name,
+               const char *closure_desc,
+               const char *ty_desc,
+               const char *label,
+               const char *module,
+               const char *srcloc );
 void flushTrace(void);
 
 #else /* !TRACING */
@@ -353,6 +361,7 @@ void flushTrace(void);
 #define traceTaskDelete_(taskID) /* nothing */
 #define traceHeapProfBegin(profile_id) /* nothing */
 #define traceHeapProfCostCentre(ccID, label, module, srcloc, is_caf) /* nothing */
+#define traceIPE(info, table_name, closure_desc, ty_desc, label, module, srcloc) /* nothing */
 #define traceHeapProfSampleBegin(era) /* nothing */
 #define traceHeapBioProfSampleBegin(era, time) /* nothing */
 #define traceHeapProfSampleEnd(era) /* nothing */