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[Analyzer][Core] Simplify IntSym in SValBuilder
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Authored by martong on Fri, Nov 12, 4:07 AM.

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Summary

Make the SimpleSValBuilder capable to simplify existing IntSym
expressions based on a newly added constraint on the sub-expression.

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Event Timeline

martong created this revision.Fri, Nov 12, 4:07 AM
martong requested review of this revision.Fri, Nov 12, 4:07 AM
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steakhal accepted this revision.Fri, Nov 12, 6:00 AM

Great stuff. Have you checked the coverage?

This revision is now accepted and ready to land.Fri, Nov 12, 6:00 AM

Great stuff. Have you checked the coverage?

Thanks for the review! So, here are the coverage results for the new test file:

1186           2 :     SVal VisitIntSymExpr(const IntSymExpr *S) {
1187           2 :       auto I = Cached.find(S);
1188           2 :       if (I != Cached.end())
1189           0 :         return I->second;
1190             :
1191           2 :       SVal RHS = Visit(S->getRHS());
1192           2 :       if (isUnchanged(S->getRHS(), RHS))
1193           0 :         return skip(S);
1194           2 :       SVal LHS = SVB.makeIntVal(S->getLHS());
1195             :       return cache(
1196           2 :           S, SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType()));
1197             :     }

L1189 is not covered, but that is related to the caching mechanism, which is already existing and this patch is independent from that. We have the very same caching implementation in all the other Visit functions.
L1193 There is an existing test case in find-binop-constraints.cpp which covers this line. :

int test_lhs_and_rhs_further_constrained(int x, int y) {
  if (x % y != 1)
    return 0;
  if (x != 1)
    return 0;
  if (y != 2)
    return 0;
  clang_analyzer_eval(x % y == 1); // expected-warning{{TRUE}}
  clang_analyzer_eval(y == 2);     // expected-warning{{TRUE}}
  return 0;
}

I could have replicated this test case here, but hadn't been able to formulate any new expectations with a clang_analyzer_ function. So there is no visible functional change in this case with this patch concerning this line. Besides, all other existing Visit functions have the same optimization and they do an early return with skip if the symbol is unchanged.

Great news, thanks.

clang/test/Analysis/svalbuilder-simplify-intsym.cpp
19

extra spaces?

This revision was automatically updated to reflect the committed changes.
martong marked an inline comment as done.Mon, Nov 22, 8:34 AM