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.

3 files changed, 37 insertions, 0 deletions

diff --git a/includes/Rts.h b/includes/Rts.h
index 50a3f665de..0f96ba2eca 100644
--- a/includes/Rts.h
+++ b/includes/Rts.h
@@ -242,6 +242,7 @@ void _assertFail(const char *filename, unsigned int linenum)
 #include "rts/PrimFloat.h"
 #include "rts/Main.h"
 #include "rts/Profiling.h"
+#include "rts/IPE.h"
 #include "rts/StaticPtrTable.h"
 #include "rts/Libdw.h"
 #include "rts/LibdwPool.h"
diff --git a/includes/rts/EventLogFormat.h b/includes/rts/EventLogFormat.h
index 4b50adfe5b..b80a9d3a94 100644
--- a/includes/rts/EventLogFormat.h
+++ b/includes/rts/EventLogFormat.h
@@ -142,6 +142,7 @@
 #define EVENT_HEAP_BIO_PROF_SAMPLE_BEGIN   166
 #define EVENT_PROF_SAMPLE_COST_CENTRE      167
 #define EVENT_PROF_BEGIN                   168
+#define EVENT_IPE                          169
 
 #define EVENT_USER_BINARY_MSG              181
 
diff --git a/includes/rts/IPE.h b/includes/rts/IPE.h
new file mode 100644
index 0000000000..81a6d553d0
--- /dev/null
+++ b/includes/rts/IPE.h
@@ -0,0 +1,35 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 2017-2018
+ *
+ * IPE API
+ *
+ * Do not #include this file directly: #include "Rts.h" instead.
+ *
+ * To understand the structure of the RTS headers, see the wiki:
+ *   https://gitlab.haskell.org/ghc/ghc/wikis/commentary/source-tree/includes
+ *
+ * -------------------------------------------------------------------------- */
+
+#pragma once
+
+
+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;
+
+extern InfoProvEnt * RTS_VAR(IPE_LIST);               // registered IP list
+
+void registerInfoProvList(InfoProvEnt **cc_list);
+InfoProvEnt * lookupIPE(StgInfoTable *info);