Stack from ghstack (oldest at bottom):

• [ExecuTorch][Vulkan] Tests for et_vk.q4gsw_requant #20946
• [ExecuTorch][Vulkan] Add et_vk.q4gsw_requant kernel (STE re-quant to W_4X8) #20945
• [ExecuTorch][Vulkan] Tests for et_vk.linear_q4gsw_backward #20944
• [ExecuTorch][Vulkan] Add et_vk.linear_q4gsw_backward kernel (4-bit input-grad) #20943
• [ExecuTorch][Vulkan] Tests for et_vk.fused_ce #20942
• [ExecuTorch][Vulkan] Add et_vk.fused_ce kernels (fused cross-entropy loss + dlogits) #20941
• [ExecuTorch][Vulkan] Tests for et_vk.linear_q4gsw_dw #20940
• [ExecuTorch][Vulkan] Add et_vk.linear_q4gsw_dw kernel (dense fp32 weight-grad GEMM) #20939
• [ExecuTorch][Vulkan] Tests for et_vk.adamw_step #20938
• [ExecuTorch][Vulkan] Add et_vk.adamw_step kernel (on-GPU AdamW optimizer step) #20937
• [ExecuTorch][WebGPU] Tests for the adamw WebGPU ops #20936
• [ExecuTorch][WebGPU] Add et_vk.adamw_step (on-GPU AdamW optimizer step) to the WebGPU backend #20935
• [ExecuTorch][WebGPU] Tests for the fused_ce WebGPU ops #20934
• [ExecuTorch][WebGPU] Add et_vk.fused_ce (fused cross-entropy) to the WebGPU backend #20933
• [ExecuTorch][WebGPU] Tests for the q4gsw_train WebGPU ops #20932
• [ExecuTorch][WebGPU] Add q4gsw training kernels (backward, weight-grad, requant) to the WebGPU backend #20931
• [ExecuTorch][WebGPU] Tests for the shape_copy WebGPU ops #20930
• [ExecuTorch][WebGPU] Add shape/copy ops (dim_order, expand_copy, fill) to the WebGPU backend #20929
• [ExecuTorch][WebGPU] Tests for the gather WebGPU ops #20928
• [ExecuTorch][WebGPU] Add gather and embedding ops to the WebGPU backend #20927
• [ExecuTorch][WebGPU] Tests for the select_bool WebGPU ops #20926
• -> [ExecuTorch][WebGPU] Add select/boolean ops (where, scalar compares, logical_not) to the WebGPU backend #20925
• [ExecuTorch][WebGPU] Tests for the reduce WebGPU ops #20924
• [ExecuTorch][WebGPU] Add reduce op (sum/mean) to the WebGPU backend #20923
• [ExecuTorch][WebGPU] Tests for the binary WebGPU ops #20922
• [ExecuTorch][WebGPU] Add elementwise binary ops (div, sub) to the WebGPU backend #20921
• [ExecuTorch][WebGPU] Tests for the softmax WebGPU ops #20920
• [ExecuTorch][WebGPU] Add softmax ops (_softmax, _log_softmax) to the WebGPU backend #20919
• [ExecuTorch][WebGPU] Tests for the matmul WebGPU ops #20918
• [ExecuTorch][WebGPU] Add fp32 matmul ops (mm, bmm, linear) to the WebGPU backend #20917

Add aten.where.self, scalar comparisons (aten.{eq,ne,le,ge,lt,gt}.Scalar), and aten.logical_not.default handlers for the training tail. The scalar compares and logical_not are generated from ONE templated byte-packed-bool shader (runtime/ops/boolean_op/) rather than per-op hand-written kernels — mirroring the binary_op codegen and Vulkan's grouping of comparison ops as ${OPERATOR} variants (backends/vulkan/runtime/graph/ops/glsl/binary_op_buffer.yaml).

Key changes:

• runtime/ops/boolean_op/ — one boolean_op.wgsl template + boolean_op.yaml (variants compare_{eq,ne,le,ge,lt,gt} + logical_not) expand to the per-variant *_wgsl.h; BooleanOp.cpp holds one shared dispatch_bool_op helper (pack 4 bools per u32 word, one thread per word) plus the seven WEBGPU_REGISTER_OPs.
• runtime/ops/where/ — ternary select, kept as its own kernel/handler (non-bool-family, as in Vulkan).
• op_registry.py — register the net-new aten.{ne,lt,le,ge,gt}.Scalar + aten.logical_not.default OpFeatures (eq.Scalar already on master).
• CMakeLists.txt WEBGPU_SRCS — wire boolean_op/BooleanOp.cpp.

aten.where.self already had Vulkan OpFeatures; the scalar-compare + logical_not registrations are additive to the shared Vulkan registry.

Co-authored-with: Claude Code.
@exported-using-ghexport

Differential Revision: D111755122

Differential Revision: D111755122