[PATCH] D31886: [analyzer] Simplify values in binary operations more aggressively

[Artem Dergachev via Phabricator via cfe-commits]

NoQ created this revision.

SValBuilder tries to constant-fold symbols in the left-hand side of the symbolic expression whenever it fails to evaluate the expression directly. However, it only constant-folds them when they are atomic expressions, not when they are complicated expressions themselves. This patch adds recursive constant-folding to the left-hand side expression (there's a lack of symmetry because we're trying to have symbols on the left and constants on the right). As an example, we'd now be able to handle operations similar to "$x + 1 < $y", when $x is constrained to a constant.

The constant-folding procedure, which i put into `SValBuilder::simplifySVal()`, is reusable, and i suspect that there are numerous places around `SValBuilder`, `ConstraintManager`, and our checkers, where it could be useful, but this patch tries to be relatively careful.

I'm still to see how it affects performance.


https://reviews.llvm.org/D31886

Files:
  include/clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h
  lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
  test/Analysis/additive-folding.cpp

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