sgatev marked an inline comment as done.
sgatev added inline comments.
================
Comment at: clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp:49
+ // in tests.
+ std::set<const CFGBlock *> Preds;
Preds.insert(Block.pred_begin(), Block.pred_end());
----------------
xazax.hun wrote:
> xazax.hun wrote:
> > Are we sure that the memory addresses of CFGBlocks are stable enough for a
> > deterministic order? Alternatively, we could use the block ids for the
> > ordering.
> Also, could you describe where the flakiness is originated from? Naively, I'd
> expect that the order in which we process the predecessors should not change
> the results of the analysis.
You're right, using block ids for ordering is better. I updated the code.
> Also, could you describe where the flakiness is originated from?
Say we have a block `B1` with predecessors `B2` and `B3`. Let the environment
of `B2` after evaluating all of its statements is `B2Env = { Expr1 -> Loc1 }`
and the environment of `B3` after evaluating all of its statement is `B3Env = {
Expr2 -> Loc2 }` where `ExprX -> LocX` refers to a particular mapping of
storage locations to expressions.
What we want for the input environment of `B1` is `{}` because `B2Env` and
`B3Env` do not contain common assignments of storage locations to expressions.
What we got before this patch is either `B2Env.join(B3Env) = { Expr1 -> Loc1 }`
or `B3Env.join(B2Env) = { Expr2 -> Loc2 }`.
Without deterministic ordering of predecessors the test that I'm introducing in
this patch is flaky.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D117754/new/
https://reviews.llvm.org/D117754
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