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, 81 insertions, 0 deletions

diff --git a/rts/IPE.c b/rts/IPE.c
new file mode 100644
index 0000000000..d881682e7d
--- /dev/null
+++ b/rts/IPE.c
@@ -0,0 +1,81 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 1998-2000
+ *
+ * Support for mapping info table pointers to source locations
+ *
+ * ---------------------------------------------------------------------------*/
+
+
+#include "PosixSource.h"
+#include "Rts.h"
+
+#include "RtsUtils.h"
+#include "Profiling.h"
+#include "Arena.h"
+#include "IPE.h"
+#include "Printer.h"
+#include "Capability.h"
+
+#include <fs_rts.h>
+#include <string.h>
+
+
+#if defined(TRACING)
+#include "Trace.h"
+#endif
+
+InfoProvEnt *IPE_LIST = NULL;
+
+void dumpIPEToEventLog(void)
+{
+#if defined(TRACING)
+    InfoProvEnt *ip, *next;
+    for (ip = IPE_LIST; ip != NULL; ip = next) {
+        next = ip->link;
+        traceIPE(ip->info, ip->prov.table_name, ip->prov.closure_desc, ip->prov.ty_desc
+                , ip->prov.label, ip->prov.module, ip->prov.srcloc);
+    }
+#endif
+    return;
+}
+
+
+/* -----------------------------------------------------------------------------
+   Registering IPEs
+
+   Registering a IPE consists of linking it onto the list of registered IPEs
+
+   IPEs are registered at startup by a C constructor function
+   generated by the compiler (ProfInit.hs) in the _stub.c file for each module.
+ -------------------------------------------------------------------------- */
+
+static void
+registerInfoProvEnt(InfoProvEnt *ipe)
+{
+        ASSERT(ipe->link == NULL);
+        ipe->link = IPE_LIST;
+        IPE_LIST = ipe;
+}
+
+void registerInfoProvList(InfoProvEnt **ent_list)
+{
+    for (InfoProvEnt **i = ent_list; *i != NULL; i++) {
+        registerInfoProvEnt(*i);
+    }
+}
+
+
+// MP: TODO: This should not be a linear search, need to improve
+// the IPE_LIST structure
+InfoProvEnt * lookupIPE(StgInfoTable *info)
+{
+    InfoProvEnt *ip, *next;
+    for (ip = IPE_LIST; ip != NULL; ip = next) {
+        if (ip->info == info) {
+            return ip;
+        }
+        next = ip->link;
+    }
+    return NULL;
+}