[PATCH] D80117: [analyzer] Introduce reasoning about symbolic remainder operator

[Valeriy Savchenko via Phabricator via cfe-commits]

vsavchenko marked an inline comment as done.
vsavchenko added inline comments.


================
Comment at: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp:459-469
+    if (Origin.From().isMinSignedValue()) {
+      // If mini is a minimal signed value, absolute value of it is greater
+      // than the maximal signed value.  In order to avoid these
+      // complications, we simply return the whole range.
+      return {ValueFactory.getMinValue(RangeType),
+              ValueFactory.getMaxValue(RangeType)};
+    }
----------------
vsavchenko wrote:
> ASDenysPetrov wrote:
> > I think you should swap `if` statements. I'll explain.
> > Let's consider the input is an **uint8** range [42, 242] and you will return [0, 242] in the second `if`.
> > But if the input is an **uint8** range [128, 242] you will return [0, 255] in the first `if`, because 128 is an equivalent of -128(INT8_MIN) in binary representation so the condition in the first if would be true.
> > What is the great difference between [42, 242] and [128, 242] to have different results? Or you've just missed this case?
> > 
> > P.S. I think your function's name doesn't fit its body, since //absolute value// is always positive (without sign) from its definition, but you output range may have negative values. You'd better write an explanation above the function and rename it.
> It is a valid point, I will add this test and change this behaviour!
> 
> The name is confusing indeed, maybe you have any ideas what would be more appropriate?
@NoQ , @ASDenysPetrov what do you think about this name instead (i.e. `getSymmetricalRange`).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80117/new/

https://reviews.llvm.org/D80117