llvm-project

b290e9ef - [OpenMPOpt] Look inside the callbacks the loop runtime functions are handed (#221449)

[OpenMPOpt] Look inside the callbacks the loop runtime functions are handed (#221449) The `__kmpc_{distribute_,for_,distribute_for_}static_loop_*` functions take the loop body as a callback, so a parallel region written inside that body is reachable from the kernel only through the runtime call. `AAKernelInfo` could not see it: it recorded an unknown reaching region, and every kernel using those functions got a worker state machine whose only option was an indirect call to whatever it was handed. Describe each function's callback argument in `OMPKinds.def`, attach `!callback` metadata, and fold the callback's `AAKernelInfo` state into the caller's, so the state machine can dispatch directly to the regions the body reaches. The two "more than one callee means give up" checks are relaxed for functions carrying `!callback`, since that edge is analyzable by construction; the conservative unknown-region record is kept for the case that motivated it, a callback we only see a declaration of. These calls still block SPMD-ization, and the `TODO` saying they need not is replaced with the obstacles that actually remain. A plain `distribute` spreads iterations over teams, so the runtime runs it with TId 0 and a team size of one; SPMD-izing has every thread run its block's whole share. The thread-indexed families are stopped by the transform rather than the analysis: guarding puts single-threaded code behind a block-wide barrier, and a barrier inside a body only some threads run is divergent. Ported from AMD's ROCm fork, `8176194f36b9`, which also used the analysis to SPMD-ize these kernels; that part is left out because it is disabled by default downstream after regressing applications. Tested on gfx90a: `llvm/test/Transforms/{OpenMP,Attributor}` 260 passed, 1 unsupported. `offload/test/amdgpu-amd-amdhsa` 516 passed, including the new Fortran reproducer. No kernel in the AOMP smoke and smoke-fort suites changes execution mode.