opencl: flash attention improvement (#25069)

* opencl: rework FA kernel for f16 and f32

* opencl: flash-attention prefill prepass kernels

- flash_attn_kv_pad_f16    pads the tail KV tile to a BLOCK_N multiple
- flash_attn_mask_pad_f16  pads the matching mask tile
- flash_attn_blk_f16       classifies each KV tile per query block as
                           fully masked / mixed / fully unmasked, so
                           the main kernel can skip fully-masked tiles
                           and the mask lookup for fully-unmasked ones

* opencl: FA kernels for q4_0 and q8_0

* opencl: `set_rows` for f32 to q8_0/q4_0

* opencl: dequant kernels for q4_0 and q8_0

* opencl: add FA tile tuning table with override

* opencl: wire host side for FA

* opencl: q4_0 MoE tensors are also SOA'ed

* opencl: cosmetic fix

* opencl: refactor, also clarify some code paths in comments

* opencl: fix inifity for `-cl-finite-math-only`

---------

Co-authored-by: Li He <lih@qti.qualcomm.com>

Author: wanghqc

ggml/src/ggml-opencl/CMakeLists.txt

@@ -192,7 +192,10 @@ set(GGML_OPENCL_KERNELS
     mul_mm_f16_f32_kq_kqv
     conv2d
     conv2d_f16_f32
+    flash_attn_pre_f16
     flash_attn_f32_f16
+    flash_attn_f32_q8_0
+    flash_attn_f32_q4_0
     flash_attn_f16
     flash_attn_f32
 )

ggml/src/ggml-opencl/fa_tune.h

@@ -0,0 +1,91 @@
+#pragma once
+
+// Flash-attention per-(dk,dv) tile tuning for the Adreno OpenCL backend.
+// Isolated from ggml-opencl.cpp so the tuning numbers are easy to find and
+// edit; the FA dispatch and kernel-compile logic stay in the main file.
+// This header is a file section — it is #included exactly once, at the point
+// in ggml-opencl.cpp where the ggml logging macros are already in scope.
+
+// Per-(dk, dv) FA config; shared by dispatch and supports_op.
+struct ggml_opencl_fa_dim {
+    int dk; int dv; int bm; int bn; int n_split; int nkv_split_threshold;
+};
+
+// Split variant fires when n_kv >= threshold (threshold=0 -> always split).
+// Default tuning covers Adreno 7xx/8xx mobile and X1-series laptop GPUs.
+static const ggml_opencl_fa_dim g_fa_dims_adreno_default[] = {
+    { 40,  40, 64, 32, 1, 0}, { 64,  64, 64, 32, 2, 64},
+    { 80,  80, 64, 32, 2, 64}, { 96,  96, 64, 32, 2, 64},
+    {112, 112, 64, 32, 2, 64}, {128, 128, 64, 32, 2, 64},
+    {192, 128, 16, 16, 1, 0},
+    {192, 192, 16, 16, 1, 0},
+    {256, 256, 16, 16, 16, 0},
+};
+
+struct ggml_opencl_fa_dim_table {
+    const ggml_opencl_fa_dim * data;
+    size_t                     count;
+
+    const ggml_opencl_fa_dim * begin() const { return data; }
+    const ggml_opencl_fa_dim * end()   const { return data + count; }
+};
+
+// Mutable copy of the active table; GGML_OPENCL_FA_TUNE patches entries here
+// at backend init without touching the const source table.
+static ggml_opencl_fa_dim g_fa_dims_runtime[
+    sizeof(g_fa_dims_adreno_default) / sizeof(g_fa_dims_adreno_default[0])];
+
+static ggml_opencl_fa_dim_table g_opencl_fa_dims = {
+    g_fa_dims_adreno_default,
+    sizeof(g_fa_dims_adreno_default) / sizeof(g_fa_dims_adreno_default[0]),
+};
+
+// GGML_OPENCL_FA_TUNE=dk:dv:bm:bn:nsplit:thr[,…] — patches matching entries
+// in the active table at backend init, before the first FA kernel compiles.
+// Unmatched (dk,dv) pairs are warned and ignored.
+static void ggml_opencl_fa_apply_env_overrides() {
+    const char * e = std::getenv("GGML_OPENCL_FA_TUNE");
+    if (!e || !e[0]) {
+        return;
+    }
+
+    std::string s = e;
+    size_t pos = 0;
+    while (pos < s.size()) {
+        size_t comma = s.find(',', pos);
+        std::string entry = s.substr(pos, comma == std::string::npos ? std::string::npos : comma - pos);
+        int dk, dv, bm, bn, nsplit, thr;
+        if (std::sscanf(entry.c_str(), "%d:%d:%d:%d:%d:%d", &dk, &dv, &bm, &bn, &nsplit, &thr) == 6) {
+            bool patched = false;
+            for (size_t i = 0; i < g_opencl_fa_dims.count; ++i) {
+                ggml_opencl_fa_dim & d = g_fa_dims_runtime[i];
+                if (d.dk == dk && d.dv == dv) {
+                    d.bm = bm; d.bn = bn; d.n_split = nsplit; d.nkv_split_threshold = thr;
+                    GGML_LOG_INFO("ggml_opencl: FA tune override DK=%d DV=%d -> bm=%d bn=%d n_split=%d thr=%d\n",
+                                  dk, dv, bm, bn, nsplit, thr);
+                    patched = true;
+                    break;
+                }
+            }
+            if (!patched) {
+                GGML_LOG_WARN("ggml_opencl: FA tune override DK=%d DV=%d ignored (no matching dim)\n", dk, dv);
+            }
+        } else {
+            GGML_LOG_WARN("ggml_opencl: FA tune override entry malformed: '%s'\n", entry.c_str());
+        }
+        if (comma == std::string::npos) break;
+        pos = comma + 1;
+    }
+}
+
+// Copy the default table into the mutable runtime buffer and apply any
+// GGML_OPENCL_FA_TUNE overrides. A per-generation table can be added here
+// once it has been tuned on hardware.
+static void ggml_cl_init_fa_dims_table() {
+    const size_t count = sizeof(g_fa_dims_adreno_default) / sizeof(g_fa_dims_adreno_default[0]);
+    for (size_t i = 0; i < count; ++i) {
+        g_fa_dims_runtime[i] = g_fa_dims_adreno_default[i];
+    }
+    g_opencl_fa_dims = { g_fa_dims_runtime, count };
+    ggml_opencl_fa_apply_env_overrides();
+}