[VL] Support LTO in builds

[zhztheplayer]

Adds option ENABLE_LTO in build to enable link-time optimization using CMake defaults.

Fixes a bug in code for LTO build.

[Copilot]

Pull request overview

Warning

Copilot couldn't run its full agentic review because it didn't start before the timeout. Make sure your repository has a runner available, or add a copilot-code-review.yml file specifying one with the runs-on attribute. See the docs for more details.

Adds a build-time ENABLE_LTO toggle to enable IPO/LTO in the CMake build, and adjusts a HUGEINT byte-reversal path to avoid an invalid loop in LTO builds.

Changes:

• Introduce --enable_lto / ENABLE_LTO plumbing in Velox and backend build scripts.
• Add CMake IPO/LTO enablement guarded by an ENABLE_LTO option with capability checks.
• Replace manual byte reversal with std::reverse_copy in HUGEINT conversion logic.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
ep/build-velox/src/build-velox.sh	Adds ENABLE_LTO argument and forwards -DVELOX_ENABLE_LTO=ON to Velox build.
dev/builddeps-veloxbe.sh	Wires --enable_lto through to Velox and Gluten CMake configuration.
cpp/velox/operators/serializer/VeloxRowToColumnarConverter.cc	Updates HUGEINT byte reversal implementation (uses reverse_copy).
cpp/CMakeLists.txt	Adds ENABLE_LTO option and enables IPO/LTO via CheckIPOSupported.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (1)

cpp/velox/operators/serializer/VeloxRowToColumnarConverter.cc:118

• bytesValue[0] is accessed even when length == 0, which is undefined behavior (and is likely the remaining issue that shows up under LTO/optimizations). The sign-extension logic should only run when at least one byte was read.

      if (length > 0) {
        std::reverse_copy(bytesValue.begin(), bytesValue.begin() + length, bytesValue2);
      }
      if (static_cast<int8_t>(bytesValue[0]) < 0) {
        memset(bytesValue2 + length, 255, 16 - length);
      }