[analyzer] Handle `[[assume(cond)]]` as `__builtin_assume(cond)`

[steakhal]

We already handle __builtin_assume calls inside the BuiltinFunctionChecker. We should also handle the attribute variant of this, e.g.: https://compiler-explorer.com/z/oq6nY7eqE

void clang_analyzer_printState();
extern int arr[10];

void using_assume_attr(int x) {
    [[assume(x > 100)]]; // NullStmt with an attribute
    //clang_analyzer_printState();
    arr[x] = 404; // FIXME: we don't raise this!
}

void using_builtin(int x) {
    __builtin_assume(x > 100); // CallExpr
    //clang_analyzer_printState();
    arr[x] = 404; // caught!
}

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

Author: Balazs Benics (steakhal)

We already handle `__builtin_assume` calls inside the `BuiltinFunctionChecker`. We should also handle the attribute variant of this, e.g.: https://compiler-explorer.com/z/oq6nY7eqE ```c++ void clang_analyzer_printState(); extern int arr[10]; void using_assume_attr(int x) { [[assume(x > 100)]]; // NullStmt with an attribute //clang_analyzer_printState(); arr[x] = 404; // FIXME: we don't raise this! } void using_builtin(int x) { __builtin_assume(x > 100); // CallExpr //clang_analyzer_printState(); arr[x] = 404; // caught! } ```

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Balazs Benics (steakhal)

We already handle `__builtin_assume` calls inside the `BuiltinFunctionChecker`. We should also handle the attribute variant of this, e.g.: https://compiler-explorer.com/z/oq6nY7eqE ```c++ void clang_analyzer_printState(); extern int arr[10]; void using_assume_attr(int x) { [[assume(x > 100)]]; // NullStmt with an attribute //clang_analyzer_printState(); arr[x] = 404; // FIXME: we don't raise this! } void using_builtin(int x) { __builtin_assume(x > 100); // CallExpr //clang_analyzer_printState(); arr[x] = 404; // caught! } ```

[vortex73]

I'm working on this issue.