[Vulkan] Make expand_copy resizable and fully delegate dynamic transformer blocks

[mergennachin]

The dynamic transformer reproductions now lower to one Vulkan delegate across changing sequence lengths. This final PR makes expand_copy resizable and adds the eager-attention and SDPA integration tests, including fully masked rows on devices with 8-bit storage buffers.

Fixes #23156.

This is part 15 of the original ghstack series. Parts 1–4 (#23240 through #23243) have landed in main; the remaining eleven PRs run from #23244 through #23254. Review each PR against its selected base branch. This PR contains the final expansion and transformer changes; part 10 owns the scalar-tensor issue #23158.

Part	PR	Change
1	#23240 (landed)	Hardware Vulkan CI
2	#23241 (landed)	Scalar cache type and signed-zero keys
3	#23242 (landed)	Vulkan-local signed-zero serialization
4	#23243 (landed)	GELU modes and view kwargs
5	#23244	Reduction clamp, NaN, and FP16 rounding
6	#23245	Reduction and arg-reduction dimension/storage guards
7	#23246	Bool staging and logical_not
8	#23247	Scalar representability and symbolic guards
9	#23248	64-bit dtype and fusion policy
10	#23249	scalar_tensor with exact integer values
11	#23250	Typed, resizable full
12	#23251	Power special values and logical FP16 dtype
13	#23252	mul.Scalar
14	#23253	any.dim with keepdim=True
15	#23254	Dynamic expand and transformer integration

The stack retains the FACTO and ATen conformance fixes and their regression tests: typed integer fills, NaN and signed-zero behavior, reduction range and accumulation fixes, safe scalar fallbacks, and the FP16 power contract. On native FP16 devices, the scalar-tensor, full texture, single-dimension texture reduction, and binary scalar shaders round their FP16 outputs to nearest-even. The binary scalar shaders also preserve the requested FP16 dtype when storage is emulated with FP32. Other operators retain their existing FP32 intermediate behavior on those devices. PR4 introduces test_vulkan_dynamic.py and its CI/Buck references.

Each code patch was linted and tested before its original publication. Prior validation of the operator changes passed 116 FACTO cases against both ATen and portable kernels, plus 144 boundary cases against ATen, with texture and buffer preferences: all 520 Vulkan-configuration executions matched ATen, including CPU fallback where unsupported. The additional 239-case sweep covers all 91 available FACTO specifications for registered ATen overloads and 57 targeted examples. Exact-input replays of every candidate Vulkan failure on a separately built main at a31838280f9309f04af1b375147375b702d29339 found no new regressions or unresolved comparisons.

Validation uses the shared backends/test/ harness on Apple M1 Pro / MoltenVK with Release portable CPU kernels and Vulkan; optimized kernels and XNNPACK are disabled. Buffer preference uses texture_limits=(1,1,1), with actual storage and fallback recorded separately. Single-texel tensors can still select textures. FACTO revision: 3b8c778c99766a8b4d0d04563ae0b16cbb276829, seed 0.

Validation: Rebased onto main at 2c8510343e47 after parts 1–4 landed. git range-diff confirms all eleven remaining patches are unchanged by this rebase. On the previous base (0b3d26d8c1f9), the Release Vulkan/portable runtime rebuilt successfully and the native suite passed 51 tests with one expected SwiftShader-only skip, before subsequent review tests were added. Coverage includes the dynamic tests, graph builder, serialization, and PT2E quantized linear with downcasting disabled. The two FP16 texture rounding tests pass 18 exact ATen cases covering both signs, signed zero, even/odd ties, exponent carry, the normal/subnormal and zero/subnormal boundaries, and values around the ±65520 overflow threshold. A separate test directly lowers int32 amax/amin to Vulkan buffers and checks exact ATen agreement beyond ±65504; the same inputs also match portable CPU execution. The arg-reduction guard update then passed four focused native tests, including 28 argmax/argmin cases checking Vulkan buffer execution and portable CPU fallback against ATen. The final rebase preserved these tested Vulkan sources; only upstream CI configuration and documentation changed. Lintrunner and git diff --check passed.

Delegation of any.dim requires keepdim=True. Omitting keepdim or setting it to False keeps the reduction on CPU, avoiding a new bool-buffer requirement for surrounding texture delegates. The default/explicit-false regression test verifies texture storage and exact ATen results across changing shapes. Five focused native tests pass on MoltenVK, including existing keepdim=True execution and the full dynamic transformer tests; lintrunner and git diff --check also pass. SwiftShader CI will verify the updated heads.

Vulkan CI will run again on the rebased ghstack heads.

Recreates #23162 through ghstack. Prior review discussion remains on that PR.

Regression coverage includes scalar exponents 2.0001 and 2049 and a two-node FP16 mul.Scalar chain. The power and chained-multiplication tests compare with ATen in both texture and buffer storage.

Authored with OpenAI Codex; split planned with Claude Code.

cc @SS-JIA @manuelcandales @digantdesai @cbilgin

[mergennachin]

Stack from ghstack (oldest at bottom):

• -> [Vulkan] Make expand_copy resizable and fully delegate dynamic transformer blocks #23254
• [Vulkan] Add aten.any.dim #23253
• [Vulkan] Delegate aten.mul.Scalar #23252
• [Vulkan] Match ATen special values in pow.Tensor_Scalar #23251
• [Vulkan] Pass typed fill values to full and make it resizable #23250
• [Vulkan] Delegate aten.scalar_tensor with exact integer values #23249
• [Vulkan] Honor downcast_64_bit=False in the partitioner #23248
• [Vulkan] Keep unrepresentable and symbolic scalars out of the delegate #23247
• [Vulkan] Stage bool tensors without 8-bit storage and register logical_not #23246
• [Vulkan] Keep reductions the reduce shaders cannot handle on CPU #23245
• [Vulkan] Stop clamping per-row reductions and propagate NaN #23244

[pytorch-bot]

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❌ 1 New Failure

As of commit 0f9c2dd with merge base 2c85103 ():

NEW FAILURE - The following job has failed:

• pull / unittest-editable / macos / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

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