[PATCH] D63279: [Analyzer] Unroll for-loops where the upper boundary is a variable with know value

Kristóf Umann via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Mon Jul 15 13:23:46 PDT 2019

Szelethus requested changes to this revision.
Szelethus added inline comments.
This revision now requires changes to proceed.

Comment at: lib/StaticAnalyzer/Core/LoopUnrolling.cpp:214-216
+  const Expr *BoundExpr = CondOp->getLHS()->IgnoreParenImpCasts();
+  if (BoundExpr == Matches[0].getNodeAs<Expr>("boundVarOperand"))
+    BoundExpr = CondOp->getRHS()->IgnoreParenImpCasts();
NoQ wrote:
> Szelethus wrote:
> > Alright, I stood on top of this for longer than I'd like to admit, what's happening here? Like, `CondExpr`, with the given testfile, should be `i < n`, right? Then `BoundExpr` is supposed to be `i`, and if that is equal to `Matches[0].getNodeAs<Expr>("boundVarOperand")` (which I guess is supposed to `n`), which I'm not sure how it could ever happen, we assign the RHS of the assignment to `BoundExpr`?
> > 
> > What does this do? Why is it needed? Which 2 test cases cover these lines?
> I think this is about `i < n` vs. `n > i`.
If that is the case, I'd be more comfortable seeing a test for it (there doesn't seem to be any) before landing this.

Comment at: lib/StaticAnalyzer/Core/LoopUnrolling.cpp:221-230
+  if (BoundNumVal.isUnknown()) {
+    if (const auto *BoundDeclRefExpr = dyn_cast<DeclRefExpr>(BoundExpr)) {
+      // FIXME: Add other declarations such as Objective-C fields
+      if (const auto *BoundVarDecl =
+              dyn_cast<VarDecl>(BoundDeclRefExpr->getDecl())) {
+        BoundNumVal = State->getSVal(
+            State->getLValue(BoundVarDecl, Pred->getLocationContext()));
NoQ wrote:
> Szelethus wrote:
> > I don't see obvious test case for which `BoundNumVal` would be unknown, am I wrong?
> We need an `ExprInspection` method that reliably produces an `UnknownVal`, because there's no truly valid reason to produce `UnknownVal` apart from "something is unimplemented".
For this too.

  rC Clang



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