BasicConstraintManager:
- Fix nonsensical logic in AssumeSymGE. When comparing 'sym >= constant' and the
constant is the maximum integer value, add the constraint that 'sym ==
constant' when the path is deemed feasible. All other cases are feasible.
- Improve AssumeSymGT. When comparing 'sym > constant' and constant is the
maximum integer value we know the path is infeasible.
- Add test case for this enhancement to AssumeSymGT.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60490 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicConstraintManager.cpp b/lib/Analysis/BasicConstraintManager.cpp
index c8065d1..f4290ff 100644
--- a/lib/Analysis/BasicConstraintManager.cpp
+++ b/lib/Analysis/BasicConstraintManager.cpp
@@ -328,6 +328,13 @@
BasicConstraintManager::AssumeSymGT(const GRState* St, SymbolID sym,
const llvm::APSInt& V, bool& isFeasible) {
+ // Is 'V' the largest possible value?
+ if (V == llvm::APSInt::getMaxValue(V.getBitWidth(), V.isSigned())) {
+ // sym cannot be any value greater than 'V'. This path is infeasible.
+ isFeasible = false;
+ return St;
+ }
+
// FIXME: For now have assuming x > y be the same as assuming sym != V;
return AssumeSymNE(St, sym, V, isFeasible);
}
@@ -341,10 +348,23 @@
isFeasible = *X >= V;
return St;
}
+
+ // Sym is not a constant, but it is worth looking to see if V is the
+ // maximum integer value.
+ if (V == llvm::APSInt::getMaxValue(V.getBitWidth(), V.isSigned())) {
+ // If we know that sym != V, then this condition is infeasible since
+ // there is no other value greater than V.
+ isFeasible = !isNotEqual(St, sym, V);
+
+ // If the path is still feasible then as a consequence we know that
+ // 'sym == V' because we cannot have 'sym > V' (no larger values).
+ // Add this constraint.
+ if (isFeasible)
+ return AddEQ(St, sym, V);
+ }
+ else
+ isFeasible = true;
- isFeasible = !isNotEqual(St, sym, V) ||
- (V != llvm::APSInt::getMaxValue(V.getBitWidth(), V.isSigned()));
-
return St;
}