[PATCH] D68714: [MCA] Show aggregate over Average Wait times for the whole snippet (PR43219)

[Andrea Di Biagio via Phabricator via llvm-commits]

andreadb added inline comments.


================
Comment at: llvm/tools/llvm-mca/Views/TimelineView.cpp:132-140
 void TimelineView::printWaitTimeEntry(formatted_raw_ostream &OS,
                                       const WaitTimeEntry &Entry,
                                       unsigned SourceIndex,
-                                      unsigned Executions) const {
-  OS << SourceIndex << '.';
+                                      unsigned CumulativeExecutions,
+                                      unsigned Executions,
+                                      bool ShouldNumber) const {
+  if (ShouldNumber)
----------------
lebedev.ri wrote:
> andreadb wrote:
> > You can still use the old signature for this method (see the explanation below):
> > 
> > We know that we are printing the special <total> entry if `SourceIndex == Source.size()`.
> > 
> > You can use that knowledge in two places:
> > 
> > 1) You can automatically infer flag `ShouldNumber`.
> > 
> > ```
> > bool ShouldNumber = SourceIndex != Source.size();
> > if (ShouldNumber)
> >   OS << SourceIndex << '.';
> > ```
> > 
> > 2) Before printing the average times,  you can check if numbers are fore he special <total> entry and modify the value of `Executions` with `Timeline.size() / Source.size()`.
> > 
> > You can do it where you currently added the FIXME comment.
> > 
> > ```
> > if (!ShouldNumber) {
> >   // override Executions for the purpose of changing colors.
> >   Executions = Timeline.size() / Source.size();
> > }
> > ```
> > 
> > Basically you don't need `CumulativeExecutions` as it can be inferred from the context. That should also fix the issue with the coloring of the output.
> To be honest i do not understand this comment.
> Is this better or worse?
> This does not help with coloring.
Okay. I see the problem now.

At line 155 we have:
```
  int BufferSize = UsedBuffer[SourceIndex].second;
```

However, SourceIndex is not a valid index if method `printWaitTimeEntry()` is called to print the <total>. The motivation is that `SourceIndex` is set to `Source.size()` for entry <total>, and there are only `Source.size()` elements in vector `UsedBuffer`. So that access is invalid if we are printing the <total>.

There is not an easy fix for it. 
I suggest for now that we avoid to change the colors if we know that we are printing the <total> entry.


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https://reviews.llvm.org/D68714