feat: add Gemma3 VLM OpenXLA path (#869)

Cargo.toml

@@ -71,6 +71,10 @@ xla-backend = ["dep:mlxcel-xla"]
 # StableHLO prefill / decode_step graphs. Needs IREE_DIST at build time (the
 # extracted iree dist), so it is a local / opt-in build, not a CI default.
 xla-iree = ["xla-backend", "mlxcel-xla/iree"]
+# Device-neutral reference capture for native IREE diagnostics. This keeps the
+# eager MLX side on its default CPU backend and qualifies IREE `local-task`
+# without requiring an IREE CUDA source/build tree.
+xla-reference-diagnostics = ["xla-iree", "mlxcel-xla/diagnostics"]
 # Explicit test-only forwarding for Gemma3n intermediate oracle validation.
 # Its pinned reference is the production CUDA runtime, so enabling diagnostics
 # also enables the root MLX CUDA backend. This is not part of `xla-iree`; normal
@@ -344,3 +348,9 @@ required-features = ["xla-micro-oracle"]
 [[example]]
 name = "xla_phi4_audio_check"
 required-features = ["xla-iree"]
+
+# Pinned #869 eager MLX CUDA versus IREE local-task Gemma3 boundary gate.
+# This is a standalone executable so running it does not link libtest.
+[[example]]
+name = "xla_gemma3_reference_check"
+required-features = ["cuda", "xla-reference-diagnostics"]

examples/xla_gemma3_reference_check.rs

@@ -0,0 +1,58 @@
+// Copyright 2025-2026 Lablup Inc. and Jeongkyu Shin
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Standalone pinned Gemma3 eager-MLX-CUDA versus IREE-local-task boundary gate.
+//!
+//! This executable intentionally avoids the Rust libtest harness. It accepts
+//! command-line arguments first and falls back to the historical environment
+//! variables used by the ignored test.
+//!
+//! ```text
+//! IREE_DIST=/path/to/iree-dist \
+//! cargo run --example xla_gemma3_reference_check \
+//!   --features cuda,xla-reference-diagnostics -- \
+//!   --model /path/to/gemma-3-4b-it-4bit \
+//!   --image tests/fixtures/test_image.png \
+//!   --device local-task
+//! ```
+
+use std::path::PathBuf;
+
+fn argument(flag: &str) -> Option<String> {
+    let args = std::env::args().collect::<Vec<_>>();
+    args.iter()
+        .position(|argument| argument == flag)
+        .and_then(|index| args.get(index + 1))
+        .cloned()
+}
+
+fn required_path(flag: &str, variable: &str) -> PathBuf {
+    argument(flag)
+        .or_else(|| std::env::var(variable).ok())
+        .map(PathBuf::from)
+        .unwrap_or_else(|| panic!("missing required {flag} or {variable}"))
+}
+
+fn main() {
+    let model = required_path("--model", "MLXCEL_GEMMA3_FIXTURE");
+    let image = argument("--image")
+        .or_else(|| std::env::var("MLXCEL_GEMMA3_IMAGE").ok())
+        .map(PathBuf::from)
+        .unwrap_or_else(|| PathBuf::from("tests/fixtures/test_image.png"));
+    let device = argument("--device")
+        .or_else(|| std::env::var("MLXCEL_XLA_DEVICE").ok())
+        .unwrap_or_else(|| "local-task".to_string());
+
+    mlxcel::run_gemma3_eager_mlx_iree_prepared_boundary(&model, &image, &device);
+}