serge-sans-paille f8c1a22220 [llvm] Improve llvm.objectsize computation by computing GEP, alloca a… (#117849) ...

…nd malloc parameters bound

Using a naive expression walker, it is possible to compute valuable
information for allocation functions, GEP and alloca, even in the
presence of some dynamic information.

We don't rely on computeConstantRange to avoid taking advantage of
undefined behavior, which would be counter-productive wrt. usual
llvm.objectsize usage.

llvm.objectsize plays an important role in _FORTIFY_SOURCE definitions,
so improving its diagnostic in turns improves the security of compiled
application.

As a side note, as a result of recent optimization improvements, clang
no longer passes
https://github.com/serge-sans-paille/builtin_object_size-test-suite This
commit restores the situation and greatly improves the scope of code
handled by the static version of __builtin_object_size.

This is a recommit of https://github.com/llvm/llvm-project/pull/115522
with fix applied.

2024-12-10 06:28:03 +00:00

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