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[Analyzer][Core] Better simplification in SimpleSValBuilder::evalBinOpNN

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Make the SValBuilder capable to simplify existing
SVals based on a newly added constraints when evaluating a BinOp.

Before this patch, we called `simplify` only in some edge cases.
However, we can and should investigate the constraints in all cases.

Differential Revision: https://reviews.llvm.org/D113753
This commit is contained in:
Gabor Marton 2021-11-11 14:55:24 +01:00
parent e13246a2ec
commit 12887a2024
2 changed files with 39 additions and 10 deletions
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19
clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
View File

@ -372,6 +372,15 @@ SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
NonLoc InputLHS = lhs;
NonLoc InputRHS = rhs;
// Constraints may have changed since the creation of a bound SVal. Check if
// the values can be simplified based on those new constraints.
SVal simplifiedLhs = simplifySVal(state, lhs);
SVal simplifiedRhs = simplifySVal(state, rhs);
if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>())
lhs = *simplifiedLhsAsNonLoc;
if (auto simplifiedRhsAsNonLoc = simplifiedRhs.getAs<NonLoc>())
rhs = *simplifiedRhsAsNonLoc;
// Handle trivial case where left-side and right-side are the same.
if (lhs == rhs)
switch (op) {
@ -619,16 +628,6 @@ SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
}
}
// Does the symbolic expression simplify to a constant?
// If so, "fold" the constant by setting 'lhs' to a ConcreteInt
// and try again.
SVal simplifiedLhs = simplifySVal(state, lhs);
if (simplifiedLhs != lhs)
if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) {
lhs = *simplifiedLhsAsNonLoc;
continue;
}
// Is the RHS a constant?
if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
return MakeSymIntVal(Sym, op, *RHSValue, resultTy);

30
clang/test/Analysis/svalbuilder-simplify-in-evalbinop.cpp Normal file
View File

@ -0,0 +1,30 @@
// RUN: %clang_analyze_cc1 %s \
// RUN: -analyzer-checker=core \
// RUN: -analyzer-checker=debug.ExprInspection \
// RUN: -analyzer-config eagerly-assume=false \
// RUN: -verify
// Here we test whether the SValBuilder is capable to simplify existing
// SVals based on a newly added constraints when evaluating a BinOp.
void clang_analyzer_eval(bool);
void test_evalBinOp_simplifies_lhs(int y) {
int x = y / 77;
if (y != 77)
return;
// Below `x` is the LHS being simplified.
clang_analyzer_eval(x == 1); // expected-warning{{TRUE}}
(void)(x * y);
}
void test_evalBinOp_simplifies_rhs(int y) {
int x = y / 77;
if (y != 77)
return;
// Below `x` is the RHS being simplified.
clang_analyzer_eval(1 == x); // expected-warning{{TRUE}}
(void)(x * y);
}