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

[Valeriy Savchenko via Phabricator via cfe-commits]

vsavchenko marked 2 inline comments as done.
vsavchenko added inline comments.


================
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)) {
----------------
ASDenysPetrov wrote:
> vsavchenko wrote:
> > 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.
> Oh, I just assumed //...Sub// at the end as a //subexpression// but you mean //subtraction//. What I'm trying to say is that we can rename it like `getRangeFor...`//the expression which this function can handle//. E.g. `getRangeForNegatedSubtractionSymSymExpr`. My point is in a speaking name.
> 
> I think //invertion// is not something appropriate in terms of applying minus operator. I think invertion of zero should be something opposite but not a zero. Because when you would like to implement the function which turns [A, B] into [MIN, A)U(B, MAX], what would be the name of it? I think this is an //invertion//.
> 
> But this is not a big deal, it's just my thoughts.
My thought process here was that we are trying to get range for `A - B` and there is also information on `B - A`, so we can get something for `A - B` based on that.  So, it doesn't really matter what it does under the hood with ranges, it matters what its semantics are.  Here I called `B - A` //an inverted subtraction//.
I don't really know what would be the best name, but I thought that this one makes more sense.


================
Comment at: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp:841-844
+  RangeSet getTrueRange(QualType T) {
+    RangeSet TypeRange = infer(T);
+    return assumeNonZero(TypeRange, T);
+  }
----------------
ASDenysPetrov wrote:
> vsavchenko wrote:
> > 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.
> I just want this function has low complexity and be more lightweight as `getFalseRange`. And if we have any chance to simplify it (and you have all the data to get MIN and MAX), it'd be cool.
`infer(QualType T)` does just that ☺️ So it is a pretty low complexity.


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

https://reviews.llvm.org/D82381