Improve GPU defaults, caching, and pointwise scheduling

[Rolaand-Jayz]

Summary

This PR improves several GPU-side MiGraphX defaults and hot paths that were leaving performance on the table, especially on recent RDNA-class parts.

Changes in this series:

• auto-tune default GPU stream count by device CU count
• select NHWC and MLIR attention defaults by architecture instead of relying on manual env tuning
• skip a redundant host bounce on final GPU fallback returns
• fix GPU linkage when MIGRAPHX_ENABLE_MLIR=Off
• cache repeated GPU feature/device-name probes
• cache repeated HIP code compilations
• cache repeated MIOpen convolution solution lookups
• avoid scheduling undersized async stream partitions
• tune untiled GPU pointwise launch bounds by wavefront size instead of falling back to oversized local=1024 launches

The pointwise launch change is the most visible runtime fix in the current OpenProteus path: on wave32 hardware it reduces PReLU-heavy pointwise kernels to local=128, which avoids the oversized launch configuration emitted previously.

Benchmark

Measured on gfx1100 with:

• model: 2x_OpenProteus_Compact_i2_70K_fp32.onnx
• shape: 8x3x192x192
• precision: fp16
• command: migraphx-driver perf --migraphx --gpu --enable-offload-copy

Latest pointwise-launch patch vs previous series head:

• previous: 11.80 ms total, 11.90 ms mean
• this branch: 8.31 ms total, 8.39 ms mean

That is roughly a 30% reduction on the isolated MiGraphX perf path for this workload.

Validation

Locally validated with:

• cmake --build ... --target migraphx_gpu driver test_gpu_jit
• test_gpu_jit compile_pointwise
• test_gpu_jit compile_pointwise_launch_bounds
• repeated migraphx-driver compile / migraphx-driver perf runs on gfx1100

Note: local validation was done in an MLIR-disabled build because this environment does not provide rocMLIR; upstream CI should cover the full build matrix.

Changelog Category

• Added: New functionality.
• Changed: Changes to existing functionality.
• Removed: Functionality or support that has been removed. (Compared to a previous release)
• Optimized: Component performance that has been optimized or improved.
• Resolved Issues: Known issues from a previous version that have been resolved.
• Not Applicable: This PR is not to be included in the changelog.

[Copilot]

Pull request overview

This PR updates MiGraphX’s GPU target defaults and hot paths to improve performance on modern AMD GPUs (notably RDNA), adding architecture-aware heuristics, caching for repeated GPU compilation/solver work, and tuning scheduler/pointwise launch behavior.

Changes:

• Add adaptive GPU stream-count defaults (based on compute unit count) and document the new MIGRAPHX_NSTREAMS=0 “adaptive” behavior.
• Make NHWC layout and MLIR attention defaults architecture-aware via new gfx_* helpers, and cache repeated device feature/name probes.
• Add caching for HIP compilation and MIOpen convolution solution lookups, plus scheduling/pointwise launch tuning and accompanying tests.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/schedule_test.cpp	Adds coverage for new scheduler split-threshold behavior.
test/gpu/jit.cpp	Adds a test ensuring pointwise launch bounds follow wavefront sizing.
test/gpu/device_name.cpp	Adds tests for new architecture-detection helpers and defaults.
test/gpu/context_serialize.cpp	Adds tests for stream-count heuristic and default stream count resolution.
test/gpu/compile_miopen_cache.cpp	New test validating MIOpen convolution solution caching.
test/gpu/compile_hip_cache.cpp	New test validating HIP compilation caching.
test/gpu/adjust_allocation.cpp	Adds test ensuring offload-copy return path avoids redundant host bounce.
src/targets/gpu/target.cpp	Enables NHWC by default on selected archs unless explicitly overridden by env.
src/targets/gpu/schedule_model.cpp	Introduces GPU split-threshold default to reduce undersized partitions.
src/targets/gpu/mlir.cpp	Fixes MLIR-disabled linkage by gating includes and adding stubbed APIs.
src/targets/gpu/lowering.cpp	Reuses host value for final return when result was only copied to GPU for pipeline reasons.
src/targets/gpu/jit/pointwise.cpp	Tunes untiled pointwise local size by wavefront size (capped).
src/targets/gpu/include/migraphx/gpu/schedule_model.hpp	Extends GPU schedule model API with split threshold.
src/targets/gpu/include/migraphx/gpu/device_name.hpp	Adds gfx_is_navi and arch-based default helper declarations.
src/targets/gpu/include/migraphx/gpu/convolution.hpp	Adds in-process caching for MIOpen convolution solution selection.
src/targets/gpu/include/migraphx/gpu/context.hpp	Adds adaptive stream-count resolver and changes default ctor behavior.
src/targets/gpu/fuse_mlir.cpp	Switches MLIR attention defaults to new arch helper logic.
src/targets/gpu/device_name.cpp	Adds cached device-info probing and implements new arch helper APIs.
src/targets/gpu/compile_hip.cpp	Adds caching of HIP compilation results to avoid repeated recompiles.
src/schedule.cpp	Plumbs new split-threshold through scheduler partitioning.
src/msgpack.cpp	Adds missing include needed for compilation.
src/include/migraphx/schedule_model.hpp	Extends type-erased scheduler model interface to include split threshold.
docs/reference/MIGraphX-dev-env-vars.rst	Documents new NHWC and adaptive stream-count default behavior.

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[anisha-amd]

Please add to the changelog as well.

[Rolaand-Jayz]

Addressed the inline review items in commit 1d810f1.

• Guarded scoped_env_var behind #ifndef _WIN32 in both cache tests so MSVC does not compile setenv/unsetenv.
• Changed get_cached_device_info() to return by value to avoid returning a reference into the cached unordered_map after unlocking.
• Added CHANGELOG.md entries under Develop / Changed and Develop / Optimized for PR Improve GPU defaults, caching, and pointwise scheduling #4668, covering the architecture-aware GPU defaults and the caching/scheduling/pointwise optimizations.