[clang] [analyzer] Support interestingness in ArrayBoundV2 (PR #78315)

[via cfe-commits]

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@@ -133,12 +195,19 @@ computeOffset(ProgramStateRef State, SValBuilder &SVB, SVal Location) {
   return std::nullopt;
 }
 
-// TODO: once the constraint manager is smart enough to handle non simplified
-// symbolic expressions remove this function. Note that this can not be used in
-// the constraint manager as is, since this does not handle overflows. It is
-// safe to assume, however, that memory offsets will not overflow.
-// NOTE: callers of this function need to be aware of the effects of overflows
-// and signed<->unsigned conversions!
+// NOTE: This function is the "heart" of this checker. It simplifies
+// inequalities with transformations that are valid (and very elementary) in
+// pure mathematics, but become invalid if we use them in C++ number model
+// where the calculations may overflow.
+// Due to the overflow issues I think it's impossible (or at least not
+// practical) to integrate this kind of simplification into the resolution of
+// arbitrary inequalities (i.e. the code of `evalBinOp`); but this function
+// produces valid results if the arguments are memory offsets which are known
+// to be << SIZE_MAX.
+// TODO: This algorithm should be moved to a central location where it's
+// available for other checkers that need to compare memory offsets.
+// NOTE: When using the results of this function, don't forget that `evalBinOp`
+// uses the evaluation rules of C++, so e.g. `(size_t)123 < -1`!
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NagyDonat wrote:

I wrote a verbose and hopefully understandable NOTE, but I think I'll do a followup commit where I'll just put a big "implementation detail, do not use externally or you'll shoot yourself in the foot" warning onto this function.

https://github.com/llvm/llvm-project/pull/78315