Reapply "[analyzer] Handle [[assume(cond)]] as __builtin_assume(cond)" (#129234)
This is the second attempt to bring initial support for [[assume()]] in
the Clang Static Analyzer.
The first attempt (#116462) was reverted in
2b9abf0db2d106c7208b4372e662ef5df869e6f1 due to some weird failure in a
libcxx test involving `#pragma clang loop vectorize(enable)
interleave(enable)`.
The failure could be reduced into:
```c++
template <class ExecutionPolicy>
void transform(ExecutionPolicy) {
#pragma clang loop vectorize(enable) interleave(enable)
for (int i = 0; 0;) { // The DeclStmt of "i" would be added twice in the ThreadSafety analysis.
// empty
}
}
void entrypoint() {
transform(1);
}
```
As it turns out, the problem with the initial patch was this:
```c++
for (const auto *Attr : AS->getAttrs()) {
if (const auto *AssumeAttr = dyn_cast<CXXAssumeAttr>(Attr)) {
Expr *AssumeExpr = AssumeAttr->getAssumption();
if (!AssumeExpr->HasSideEffects(Ctx)) {
childrenBuf.push_back(AssumeExpr);
}
}
// Visit the actual children AST nodes.
// For CXXAssumeAttrs, this is always a NullStmt.
llvm::append_range(childrenBuf, AS->children()); // <--- This was not meant to be part of the "for" loop.
children = childrenBuf;
}
return;
```
The solution was simple. Just hoist it from the loop.
I also had a closer look at `CFGBuilder::VisitAttributedStmt`, where I also spotted another bug.
We would have added the CFG blocks twice if the AttributedStmt would have both the `[[fallthrough]]` and the `[[assume()]]` attributes. With my fix, it will only once add the blocks. Added a regression test for this.
Co-authored-by: Vinay Deshmukh <vinay_deshmukh AT outlook DOT com>
llvm-project
7e5821ba - Reapply "[analyzer] Handle [[assume(cond)]] as __builtin_assume(cond)" (#129234)
