Hexagon backend has incorrect definition for round

[abadams]

It redirects it to nearbyint, which is then implemented in the runtime as floor(x + 0.5), which rounds ties towards +inf

[abadams]

Note

Automated triage: this issue was flagged by Claude as likely safe to close, for the reason below. The reasoning was checked against the current source, and a second pass tried and failed to refute it, but no human verified this specific text. If the reason is wrong, please reopen the issue and say so — some fraction of these are expected to be wrong.

Reason (CLOSE_FIXED): Halide::round no longer goes through nearbyint/floor(x + 0.5) on any backend. It is now a Call::round intrinsic lowered to llvm.roundeven, with a target-independent ties-to-even software fallback when the intrinsic is unavailable, and test/correctness/round.cpp checks the ties-to-even results (including -2.5 -> -2, 2.5 -> 2).

Evidence: Commit d5a81186a "Make Halide::round behave as documented (#7012)" (its changelog includes "Work around hexagon issue"); src/CodeGen_LLVM.cpp:3102-3107 (Call::round -> roundeven, else lower_round_to_nearest_ties_to_even); src/CodeGen_Internal.cpp:528-560; test/correctness/round.cpp:140,176.

Closing: fixed by #7012 (d5a81186a). Halide::round is now a Call::round intrinsic lowered to llvm.roundeven, with the target-independent ties-to-even fallback in lower_round_to_nearest_ties_to_even (src/CodeGen_Internal.cpp:531) when that intrinsic isn't available; nearbyint is no longer used for it, and test/correctness/round.cpp covers the ties-to-even semantics.