AllocaInst::getAllocationSize/AllocaInst::getAllocationSizeInBits should check for overflow

[efriedma-quic]

Currently, the code just blindly multiplies the size, and can therefore return a nonsense result. (The behavior isn't really defined in the overflow case, but reasoning based on the overflowed computation is likely to lead to weird results.)

llvm-project/llvm/lib/Transforms/Utils/InlineFunction.cpp

Line 2622 in 7115ed0

// Try to determine the size of the allocation.

has code to compute the allocation size while conservatively checking for overflow; we should use similar logic, then make the inliner call getAllocationSize(). Maybe use the multiply-with-overflow helper from CheckedArithmetic.h instead of writing out that code.

[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-good-first-issue

Author: Eli Friedman (efriedma-quic)

Currently, the code just blindly multiplies the size, and can therefore return a nonsense result. (The behavior isn't really defined in the overflow case, but reasoning based on the overflowed computation is likely to lead to weird results.)

llvm-project/llvm/lib/Transforms/Utils/InlineFunction.cpp

Line 2622 in 7115ed0

// Try to determine the size of the allocation.

has code to compute the allocation size while conservatively checking for overflow; we should use similar logic, then make the inliner call getAllocationSize(). Maybe use the multiply-with-overflow helper from CheckedArithmetic.h instead of writing out that code.

[moghya]

Hi @efriedma-quic could you please assign this to me, I would like to work and get this fixed. Thanks.

[cjkenn]

@moghya are you still looking into this?

[tszhin-swe]

@cjkenn can i be assigned? thx