eventlog: Dump cost centre stack on each sample

With this change it is possible to reconstruct the timing portion of a
`.prof` file after the fact. By logging the stacks at each time point
a more precise executation trace of the program can be observed rather
than all identical cost centres being identified in the report.

There are two new events:

1. `EVENT_PROF_BEGIN` - emitted at the start of profiling to communicate
the tick interval
2. `EVENT_PROF_SAMPLE_COST_CENTRE` - emitted on each tick to communicate the
current call stack.

Fixes #17322

1 files changed, 4 insertions, 0 deletions

diff --git a/rts/Trace.h b/rts/Trace.h
index d3bb226000..b7db0ca912 100644
--- a/rts/Trace.h
+++ b/rts/Trace.h
@@ -301,6 +301,10 @@ void traceHeapProfCostCentre(StgWord32 ccID,
                              StgBool is_caf);
 void traceHeapProfSampleCostCentre(StgWord8 profile_id,
                                    CostCentreStack *stack, StgWord residency);
+
+void traceProfSampleCostCentre(Capability *cap,
+                               CostCentreStack *stack, StgWord ticks);
+void traceProfBegin(void);
 #endif /* PROFILING */
 
 void flushTrace(void);