[PATCH] D82381: [analyzer] Introduce small improvements to the solver infra

[Valeriy Savchenko via Phabricator via cfe-commits]

vsavchenko marked 3 inline comments as done.
vsavchenko added a comment.

Hi @ASDenysPetrov no problem at all!  Thanks for taking your time and checking it.



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Comment at: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp:367-378
+RangeSet RangeSet::Delete(BasicValueFactory &BV, Factory &F,
+                          const llvm::APSInt &Point) const {
+  llvm::APSInt Upper = Point;
+  llvm::APSInt Lower = Point;
+
+  ++Upper;
+  --Lower;
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ASDenysPetrov wrote:
> Useful function. But I'd better rename it to `subtract` as we are working with sets (as a mathimatical collection). We should have a such one for the Ranges not only for Points.
> We have `intersect`, `delete` aka `subtract`. And we also need to have functions `union` and `symmetricDifference` to cover full palette of common operations on sets.
I agree that we should have a full set of functions.  I don't agree however, that this function is a `subtract`.  Subtract is an operation on two sets and here we have a set and a point.  One might argue that a point is just a very simple set, that's true, but real `subtract` would be more complex in its implementation.

Naming it `delete`, on the other hand, I was coming from a notion of deleting points or neighbourhoods (https://en.wikipedia.org/wiki/Neighbourhood_(mathematics)#Deleted_neighbourhood).


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Comment at: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp:734
   //        expressions which we currently do not know how to negate.
-  const RangeSet *getRangeForMinusSymbol(ProgramStateRef State, SymbolRef Sym) {
+  Optional<RangeSet> getRangeForInvertedSub(SymbolRef Sym) {
     if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(Sym)) {
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ASDenysPetrov wrote:
> As for me, I'd call this like `getRangeForNegatedSymSymExpr`, since you do Negate operation inside.
I'm not super happy about my name either, but I feel like it describes it better than the previous name and your version.  That function doesn't work for any `SymSymExpr` and it doesn't simply negate whatever we gave it.  It works specifically for symbolic subtractions and this is the information I want to be reflected in the name.


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Comment at: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp:841-844
+  RangeSet getTrueRange(QualType T) {
+    RangeSet TypeRange = infer(T);
+    return assumeNonZero(TypeRange, T);
+  }
----------------
ASDenysPetrov wrote:
> Don't you think this is too complicated for such a simple getter?
> Maybe we can just construct the range using smth about `RangeSet(RangeFactory, ++Zero, --Zero);` ?
It is more complex than a false range but there is a reason for it.

First of all, `RangeSet` can't have ranges where the end is greater than its start.  Only `Intersect` can handle such ranges correctly.  Another thing is that ranges like that mean `[MIN, --Zero], [++Zero, MAX]` and without a type we can't really say what `MIN` and `MAX` are, so such constructor for `RangeSet` simply cannot exist.

Another point is that we do need to have `[MIN, -1], [+1, MAX]` as opposed to `[-1, -1], [+1, +1]` because of C language (it doesn't have boolean type), and because of the cases like `a - b` where we know that `a != b`.

I hope that answers the question.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D82381/new/

https://reviews.llvm.org/D82381