xazax.hun accepted this revision.
xazax.hun added a comment.
Thanks!
================
Comment at: clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp:35
+ TypeErasedDataflowAnalysis &Analysis) {
+ TypeErasedDataflowAnalysisState State = {Analysis.typeErasedInitialElement(),
+ InitEnv};
----------------
sgatev wrote:
> xazax.hun wrote:
> > I did not catch this earlier, but I wonder if we should pass the block in
> > to `typeErasedInitialElement`. There are some analysis where the initial
> > element might be different for certain nodes. E.g. here is the algorithms
> > for computing dominators from wikipedia:
> > ```
> > // dominator of the start node is the start itself
> > Dom(n0) = {n0}
> > // for all other nodes, set all nodes as the dominators
> > for each n in N - {n0}
> > Dom(n) = N;
> > // iteratively eliminate nodes that are not dominators
> > while changes in any Dom(n)
> > for each n in N - {n0}:
> > Dom(n) = {n} union with intersection over Dom(p) for all p in
> > pred(n)
> > ```
> >
> > Here the initial analysis state for the entry node differs from the initial
> > state for the rest of the nodes.
> Good point, though, I'm not sure if this algorithm is the best choice for
> such an analysis. It seems that in that case we don't need to evaluate the
> statements in the basic blocks, right? Perhaps we can generalize the
> algorithm or offer a separate one for more efficient implementation of such
> analyses. I added a FIXME and will consider this a bit more.
Dominators is one example, but there might be other analyses where the initial
state differs :)
Since this change is really easy to make, I'm ok deferring this until we see
the actual need.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D115235/new/
https://reviews.llvm.org/D115235
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