[all-commits] [llvm/llvm-project] 3621db: [Clang][OpenMP] Fix crash on `_BitInt` loop bounds...

[Akash Manna via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3621db6aff701dcd9e6ff54ea281d24ee2f43448
      https://github.com/llvm/llvm-project/commit/3621db6aff701dcd9e6ff54ea281d24ee2f43448
  Author: Akash Manna <akash.manna.mymail at gmail.com>
  Date:   2026-09-25 (Fri, 25 Sep 2026)

  Changed paths:
    M clang/docs/ReleaseNotes.md
    M clang/lib/Sema/SemaOpenMP.cpp
    A clang/test/OpenMP/for_loop_bitint_messages.c

  Log Message:
  -----------
  [Clang][OpenMP] Fix crash on `_BitInt` loop bounds and counters in loop analysis (#226464)

Fixes #140074

When building the iteration count of an OpenMP loop, Sema derives a few
integer types from bit widths, e.g. to promote the upper bound to an
unsigned type as wide as the wider bound so that `upper - lower` cannot
overflow. Those types came from `ASTContext::getIntTypeForBitwidth`,
which only knows the standard integer widths and returns a null type for
anything else. With a bound or loop counter of type `_BitInt(931)` the
request was for a 960-bit type, the result was null, and it went
straight into `PerformImplicitConversion`, which asserted. The
`collapse(2)` in the reduced reproducer is incidental; a plain `#pragma
omp for` on the same loop crashes the same way.

The loop analysis now goes through a small helper that asks for the
standard type first and otherwise builds the `_BitInt` type of that
width and signedness with `ASTContext::getBitIntType`. It is used at the
three places that derive a type from a loop width: the upper-bound
promotion in `calculateNumIters`, the conversion to the loop variable's
width in `buildNumIterations`, and the logical iteration type in
`ActOnOpenMPCanonicalLoop`. Wide `_BitInt` loop variables are then
narrowed to the runtime's 64-bit iteration variable with the existing
warning, the same as `__int128` today.



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