Optimize Info Table Provenance Entries (IPEs) Map creation and lookup

Using a hash map reduces the complexity of lookupIPE(), making it non linear.

On registration each IPE list is added to a temporary IPE lists buffer, reducing
registration time. The hash map is built lazily on first lookup.

IPE event output to stderr is added with tests.

For details, please see
Note [The Info Table Provenance Entry (IPE) Map].

A performance test for IPE registration and lookup can be found here:
https://gitlab.haskell.org/ghc/ghc/-/merge_requests/5724#note_370806

1 files changed, 11 insertions, 0 deletions

diff --git a/rts/Trace.c b/rts/Trace.c
index d08b19a69d..8f2877a536 100644
--- a/rts/Trace.c
+++ b/rts/Trace.c
@@ -668,6 +668,17 @@ void traceIPE(StgInfoTable * info,
               const char *module,
               const char *srcloc )
 {
+#if defined(DEBUG)
+    if (RtsFlags.TraceFlags.tracing == TRACE_STDERR) {
+        ACQUIRE_LOCK(&trace_utx);
+
+        tracePreface();
+        debugBelch("IPE: table_name %s, closure_desc %s, ty_desc %s, label %s, module %s, srcloc %s\n",
+                   table_name, closure_desc, ty_desc, label, module, srcloc);
+
+        RELEASE_LOCK(&trace_utx);
+    } else
+#endif
     if (eventlog_enabled) {
         postIPE((W_) INFO_PTR_TO_STRUCT(info), table_name, closure_desc, ty_desc, label, module, srcloc);
     }