Commit df750f76b for llama.cpp
commit df750f76bb6126566621803b69ddaeb993be5b08
Author: WakeUpMorty <balogkarlo4@gmail.com>
Date: Wed Sep 9 08:26:36 2026 +0200
vulkan: add dedicated iq4_xs mat-vec shader (#28426)
* vulkan: add dedicated iq4_xs mat-vec shader
Dedicated mul_mat_vec_iq4_xs for the dmmv path, replacing the generic fallback. ~+6-17% token generation on RDNA4 depending on model.
Assisted-by: Pi agent with Qwen3.8 27B
* vulkan iq4_xs: remove dead n_it unroll branch
Remove the n_it <= 8 experimental branch that attempted to fully unroll
the block loop. Since n_it is a runtime value, [[unroll]] is ignored by
the compiler, making both branches equivalent. Kept the simple loop
matching mul_mat_vec_iq3_s.comp.
diff --git a/ggml/src/ggml-vulkan/vulkan-shaders/mul_mat_vec_iq4_xs.comp b/ggml/src/ggml-vulkan/vulkan-shaders/mul_mat_vec_iq4_xs.comp
new file mode 100644
index 000000000..a2b99d9ab
--- /dev/null
+++ b/ggml/src/ggml-vulkan/vulkan-shaders/mul_mat_vec_iq4_xs.comp
@@ -0,0 +1,97 @@
+#version 450
+
+#extension GL_EXT_shader_explicit_arithmetic_types_int32 : require
+
+#include "mul_mat_vec_base.glsl"
+
+layout(local_size_x_id = 0, local_size_y = 1, local_size_z = 1) in;
+
+FLOAT_TYPE temp[NUM_COLS][NUM_ROWS];
+
+// dedicated iq4_xs mat-vec, mirrors mul_mat_vec_iq3_s.comp
+// one packed32 word per l, so the 6-bit subblock scale is hoisted to a single fma after register accumulation
+
+void calc_superblock(const uint a_offset, const uint b_offset, const uint ib32, const uint i, const uint num_blocks_per_row, const uint first_row, const uint num_rows) {
+ const uint y_idx = i * QUANT_K + 32 * ib32;
+
+ uint ibi = a_offset + first_row * num_blocks_per_row + i;
+ [[unroll]] for (uint n = 0; n < num_rows; ++n) {
+ const float d = float(data_a[ibi].d);
+ const uint sl = (data_a[ibi].scales_l[ib32/2] >> (4 * (ib32 & 1))) & 0xF;
+ const uint sh = (data_a[ibi].scales_h >> (2 * ib32)) & 3;
+ const float dscale = d * float(int(sl | (sh << 4)) - 32);
+
+ FLOAT_TYPE sum[NUM_COLS];
+ [[unroll]] for (uint j = 0; j < NUM_COLS; ++j) {
+ sum[j] = FLOAT_TYPE(0);
+ }
+
+ [[unroll]] for (uint l = 0; l < 4; ++l) {
+ const uint w = data_a_packed32[ibi].qs[4 * ib32 + l];
+ const u8vec4 q0 = unpack8(w & 0x0F0F0F0F);
+ const u8vec4 q1 = unpack8((w >> 4) & 0x0F0F0F0F);
+
+ [[unroll]] for (uint j = 0; j < NUM_COLS; ++j) {
+ const vec4 b0 = vec4(data_b_v4[(j*p.batch_stride_b + b_offset + y_idx) / 4 + l]);
+ const vec4 b1 = vec4(data_b_v4[(j*p.batch_stride_b + b_offset + y_idx) / 4 + 4 + l]);
+
+ sum[j] = fma(FLOAT_TYPE(b0.x), FLOAT_TYPE(kvalues_iq4nl[q0.x]),
+ fma(FLOAT_TYPE(b0.y), FLOAT_TYPE(kvalues_iq4nl[q0.y]),
+ fma(FLOAT_TYPE(b0.z), FLOAT_TYPE(kvalues_iq4nl[q0.z]),
+ fma(FLOAT_TYPE(b0.w), FLOAT_TYPE(kvalues_iq4nl[q0.w]),
+ fma(FLOAT_TYPE(b1.x), FLOAT_TYPE(kvalues_iq4nl[q1.x]),
+ fma(FLOAT_TYPE(b1.y), FLOAT_TYPE(kvalues_iq4nl[q1.y]),
+ fma(FLOAT_TYPE(b1.z), FLOAT_TYPE(kvalues_iq4nl[q1.z]),
+ fma(FLOAT_TYPE(b1.w), FLOAT_TYPE(kvalues_iq4nl[q1.w]),
+ sum[j]))))))));
+ }
+ }
+
+ [[unroll]] for (uint j = 0; j < NUM_COLS; ++j) {
+ temp[j][n] = fma(dscale, sum[j], temp[j][n]);
+ }
+
+ ibi += num_blocks_per_row;
+ }
+}
+
+void compute_outputs(const uint32_t first_row, const uint32_t num_rows) {
+ uint a_offset, b_offset, d_offset;
+
+ get_offsets(a_offset, b_offset, d_offset);
+
+ const uint num_blocks_per_row = p.ncols / QUANT_K;
+
+ // 8 threads are used to process each block
+ const uint blocks_per_wg = gl_WorkGroupSize.x/8;
+ const uint tid = gl_LocalInvocationID.x;
+ const uint itid = tid % 8; // 0...7
+ const uint ix = tid / 8;
+
+ [[unroll]] for (uint j = 0; j < NUM_COLS; ++j) {
+ [[unroll]] for (uint i = 0; i < NUM_ROWS; ++i) {
+ temp[j][i] = FLOAT_TYPE(0);
+ }
+ }
+
+ [[unroll]] for (uint i = ix; i < num_blocks_per_row; i += blocks_per_wg)
+ calc_superblock(a_offset, b_offset, itid, i, num_blocks_per_row, first_row, num_rows);
+
+ reduce_result(temp, d_offset, first_row, num_rows, tid);
+}
+
+void main() {
+ const uint first_row = NUM_ROWS * (gl_WorkGroupID.x + gl_NumWorkGroups.x * gl_WorkGroupID.z);
+
+ init_iq_shmem(gl_WorkGroupSize);
+
+ // do NUM_ROWS at a time, unless there aren't enough remaining rows
+ if (first_row + NUM_ROWS <= p.stride_d) {
+ compute_outputs(first_row, NUM_ROWS);
+ } else {
+ if (first_row >= p.stride_d) {
+ return;
+ }
+ compute_outputs(first_row, p.stride_d - first_row);
+ }
+}
diff --git a/ggml/src/ggml-vulkan/vulkan-shaders/vulkan-shaders-gen.cpp b/ggml/src/ggml-vulkan/vulkan-shaders/vulkan-shaders-gen.cpp
index cb1128dcc..ea4851b7a 100644
--- a/ggml/src/ggml-vulkan/vulkan-shaders/vulkan-shaders-gen.cpp
+++ b/ggml/src/ggml-vulkan/vulkan-shaders/vulkan-shaders-gen.cpp
@@ -735,7 +735,7 @@ void process_shaders() {
for (const auto& tname : type_names) {
// mul mat vec
std::string data_a_key = "DATA_A_" + to_uppercase(tname);
- std::string shader = (string_ends_with(tname, "_k") || string_starts_with(tname, "iq1_") || string_starts_with(tname, "iq2_") || string_starts_with(tname, "iq3_") || tname == "tq2_0" || tname == "tq1_0") ? "mul_mat_vec_" + tname + ".comp" : "mul_mat_vec.comp";
+ std::string shader = (string_ends_with(tname, "_k") || string_starts_with(tname, "iq1_") || string_starts_with(tname, "iq2_") || string_starts_with(tname, "iq3_") || tname == "iq4_xs" || tname == "tq2_0" || tname == "tq1_0") ? "mul_mat_vec_" + tname + ".comp" : "mul_mat_vec.comp";
string_to_spv("mul_mat_vec_" + tname + "_f32_f32", shader, merge_maps(base_dict, {{data_a_key, "1"}, {"B_TYPE", "float"}, {"B_TYPEV2", "vec2"}, {"B_TYPEV4", "vec4"}, {"D_TYPE", "float"}}));
string_to_spv("mul_mat_vec_" + tname + "_f16_f32", shader, merge_maps(base_dict, {{data_a_key, "1"}, {"B_TYPE", "float16_t"}, {"B_TYPEV2", "f16vec2"}, {"B_TYPEV4", "f16vec4"}, {"D_TYPE", "float"}}));