Hexagon add support for f16/f32 flash attention, scale, set-rows and improve f16/32 matmul (#18611)

* hexagon: improve fp16 matmul and add fp32/fp16 flash-attention

* hexagon: add support for set-rows fp32 -> fp16 with i32/i64 row-idx

* hexagon: add support for SCALE fp32

* hexagon: replace scalar fp32 -> fp16 copy with HVX

* hexagon: optimize flash_atten_ext with aligned VTCM buffers and DMA

- Implements double-buffered DMA prefetching for K, V, and Mask tensors.
- Ensures K and V rows in VTCM are padded to 128 bytes to support aligned HVX operations.
- Correctly synchronizes DMA transfers to prevent race conditions.
- Uses `FLASH_ATTN_BLOCK_SIZE` of 128 for efficient chunking.

* hexagon: use aligned mad_f16

* hexagon: flash_atten more aligned ops

* hexagon: optimize scale_f32 hvx helpers

* hexagon: unroll fa loops

* hexagon: remove unused set-rows log

* hexagon: flash_attn_ext add support for DMAing Q

- Update `op_flash_attn_ext` to include Q row size in scratchpad allocation.
- Pad Q row size to 128 bytes for alignment.
- Implement DMA transfer for Q tensor in `flash_attn_ext_f16_thread`.
- Update dot product computations to use VTCM-buffered Q data.

* hexagon: fix handling of NANs hvx dotproducts

* hexagon: cleanup spad allocation in flash-atten

* hexagon: improve fp16/fp32 matmul

- Introduced `vec_dot_f16_f16` and `vec_dot_f16_f16_rx2` kernels using efficient HVX dot product intrinsics.
- Added `quantize_fp32_f16` to copy/convert weights from DDR to VTCM
- Updated `op_matmul` to use the optimized path when VTCM capacity allows and broadcasting requirements are compatible.
- Implemented fallback logic to the original implementation for complex broadcasting scenarios.

* hexagon: fix HVX_ARCH check

* hexagon: matmul cleanup and fp16 fixes

Use aligned vec_dot_f16 for 2d matmuls and unaligned version for 4d.

* hexagon: fix fp16 x fp16 matmuls and some minor refactoring

* hexagon: add support for GET_ROWS f32 -> f32

Also optimize SET_ROWS threading a bit when we have just a few rows to process.

* hexagon: optimize set-rows threading

* hexagon: update adb/run-bench.sh to properly support experimental and verbose options

* hexagon: flash_atten use aligned vectors for dot products

ggml/src/ggml-hexagon/htp/get-rows-ops.c

@@ -0,0 +1,112 @@
+#pragma clang diagnostic ignored "-Wunused-variable"
+#pragma clang diagnostic ignored "-Wunused-function"
+#pragma clang diagnostic ignored "-Wunused-but-set-variable"
+
+#ifdef HTP_DEBUG
+#    define FARF_HIGH 1
+#endif
+#include <HAP_farf.h>
+#include <HAP_mem.h>
+#include <HAP_perf.h>
+#include <hexagon_protos.h>
+#include <hexagon_types.h>
+#include <math.h>
+#include <string.h>
+
+#define GGML_COMMON_DECL_C
+#include "ggml-common.h"
+#include "htp-ctx.h"
+#include "htp-msg.h"
+#include "htp-ops.h"
+#include "hvx-utils.h"
+#include "ops-utils.h"
+
+#define get_rows_preamble \
+    const uint32_t ne00 = octx->src0.ne[0]; \
+    const uint32_t ne01 = octx->src0.ne[1]; \
+    const uint32_t ne02 = octx->src0.ne[2]; \
+    const uint32_t ne03 = octx->src0.ne[3]; \
+                                            \
+    const uint32_t ne10 = octx->src1.ne[0]; \
+    const uint32_t ne11 = octx->src1.ne[1]; \
+    const uint32_t ne12 = octx->src1.ne[2]; \
+                                            \
+    const uint32_t nb01 = octx->src0.nb[1]; \
+    const uint32_t nb02 = octx->src0.nb[2]; \
+    const uint32_t nb03 = octx->src0.nb[3]; \
+                                            \
+    const uint32_t nb10 = octx->src1.nb[0]; \
+    const uint32_t nb11 = octx->src1.nb[1]; \
+    const uint32_t nb12 = octx->src1.nb[2]; \
+                                            \
+    const uint32_t nb1 = octx->dst.nb[1];   \
+    const uint32_t nb2 = octx->dst.nb[2];   \
+    const uint32_t nb3 = octx->dst.nb[3];   \
+                                            \
+    const uint32_t nr = ne10 * ne11 * ne12;
+
+static int get_rows_thread_f32_f32(struct htp_ops_context * octx, const int nth, const int ith) {
+    get_rows_preamble;
+
+    // parallelize by src1 elements (which correspond to dst rows)
+    const uint32_t dr  = octx->src1_nrows_per_thread;
+    const uint32_t ir0 = dr * ith;
+    const uint32_t ir1 = (ir0 + dr < nr) ? (ir0 + dr) : nr;
+
+    const bool is_i32 = (octx->src1.type == HTP_TYPE_I32);
+
+    for (uint32_t i = ir0; i < ir1; ++i) {
+        const uint32_t i12 = fastdiv(i, &octx->get_rows_div_ne10_ne11);
+        const uint32_t rem = i - i12 * ne11 * ne10;
+        const uint32_t i11 = fastdiv(rem, &octx->get_rows_div_ne10);
+        const uint32_t i10 = rem - i11 * ne10;
+
+        const uintptr_t src1_addr = octx->src1.data + i10*nb10 + i11*nb11 + i12*nb12;
+
+        uint32_t i01 = is_i32 ? *(int32_t *)src1_addr : *(int64_t *)src1_addr;
+
+        if (i01 >= ne01) {
+            // invalid index, skip for now to avoid crash
+            continue;
+        }
+
+        const uintptr_t src0_ptr = octx->src0.data + i01*nb01 + i11*nb02 + i12*nb03;
+        const uintptr_t dst_ptr  = octx->dst.data  + i10*nb1  + i11*nb2  + i12*nb3;
+        hvx_copy_fp32_uu((uint8_t *)dst_ptr, (const uint8_t *)src0_ptr, ne00);
+    }
+
+    return HTP_STATUS_OK;
+}
+
+static void get_rows_work_f32_f32(unsigned int n, unsigned int i, void *data) {
+    get_rows_thread_f32_f32((struct htp_ops_context *) data, n, i);
+}
+
+int op_get_rows(struct htp_ops_context * octx) {
+    get_rows_preamble;
+
+    if (octx->src0.type != HTP_TYPE_F32) {
+        return HTP_STATUS_NO_SUPPORT;
+    }
+
+    if (octx->dst.type != HTP_TYPE_F32) {
+        return HTP_STATUS_NO_SUPPORT;
+    }
+
+    if (octx->src1.type != HTP_TYPE_I32 && octx->src1.type != HTP_TYPE_I64) {
+        return HTP_STATUS_NO_SUPPORT;
+    }
+
+    if (octx->flags & HTP_OPFLAGS_SKIP_COMPUTE) {
+        return HTP_STATUS_OK;
+    }
+
+    octx->get_rows_div_ne10      = init_fastdiv_values(octx->src1.ne[0]);
+    octx->get_rows_div_ne10_ne11 = init_fastdiv_values(octx->src1.ne[0] * octx->src1.ne[1]);
+
+    const uint32_t n_jobs = MIN(nr, octx->n_threads);
+    octx->src1_nrows_per_thread = (nr + n_jobs - 1) / n_jobs;
+
+    worker_pool_run_func(octx->ctx->worker_pool, get_rows_work_f32_f32, octx, n_jobs);
+    return HTP_STATUS_OK;
+}