vulkan: reduce iq1 shared memory usage for mul_mm (ggml-org#24287)

Author: jeffbolznv

ggml/src/ggml-vulkan/ggml-vulkan.cpp

@@ -3394,7 +3394,9 @@ static bool ggml_vk_matmul_shmem_support(const vk_device& device, const std::vec
     switch (src0_type) {
     case GGML_TYPE_IQ1_S:
     case GGML_TYPE_IQ1_M:
-        lut_size = 2*2048 + 4*2048;
+        // Regular matmul uses the compact uint16_t IQ1 grid; the expanded
+        // uint32_t grid is only enabled for the q8_1/int-dot vector path.
+        lut_size = 2*2048;
         break;
     case GGML_TYPE_IQ2_XXS:
         lut_size = 8*256;

ggml/src/ggml-vulkan/vulkan-shaders/mul_mat_vecq.comp

@@ -4,6 +4,7 @@
 #extension GL_EXT_integer_dot_product : require
 
 #define MMQ
+#define NEEDS_IQ1S_GRID_GPU
 #define B_TYPE block_q8_1_x4
 
 #include "mul_mat_vec_base.glsl"

ggml/src/ggml-vulkan/vulkan-shaders/types.glsl

@@ -598,9 +598,10 @@ const uint[1024] iq1s_grid_const = {
     0x55dd55df, 0x55d555d7, 0x5503550c, 0x557f5501, 0x5577557d, 0x55405575, 0x555d555f, 0x55555557
 };
 
+#if defined(NEEDS_IQ1S_GRID_GPU)
 // Same content as iq1s_grid_const except each 2-bit value is expanded to 4-bit
 // and has 1 added to it (allows packed values to be extracted with & 0x0F0F0F0F
-// and 0xF0F0F0F0).
+// and 0xF0F0F0F0). This is only used by the q8_1/int-dot vector path.
 const uint32_t[2048] iq1s_grid_gpu_const = {
     0x00000000, 0x00000002, 0x00000101, 0x00000200, 0x00000202, 0x00010001, 0x00010101, 0x00020000,
     0x00020002, 0x00020200, 0x00020202, 0x01000101, 0x01010001, 0x01010100, 0x01010102, 0x01020101,
@@ -859,9 +860,12 @@ const uint32_t[2048] iq1s_grid_gpu_const = {
     0x20222020, 0x20222022, 0x20222220, 0x20222222, 0x21212021, 0x21212120, 0x21212122, 0x22202020,
     0x22202022, 0x22202220, 0x22202222, 0x22212121, 0x22222020, 0x22222022, 0x22222220, 0x22222222,
 };
+#endif
 
 shared uint16_t iq1s_grid[2048];
+#if defined(NEEDS_IQ1S_GRID_GPU)
 shared uint32_t iq1s_grid_gpu[2048];
+#endif
 
 #define NEEDS_INIT_IQ_SHMEM
 void init_iq_shmem(uvec3 wgsize)
@@ -875,12 +879,14 @@ void init_iq_shmem(uvec3 wgsize)
             iq1s_grid[2*idx+1] = g.y;
         }
     }
+#if defined(NEEDS_IQ1S_GRID_GPU)
     [[unroll]] for (uint i = 0; i < iq1s_grid_gpu_const.length(); i += wgsize.x) {
         uint idx = i + gl_LocalInvocationIndex.x;
         if (iq1s_grid_gpu_const.length() % wgsize.x == 0 || idx < iq1s_grid_gpu_const.length()) {
             iq1s_grid_gpu[idx] = iq1s_grid_gpu_const[idx];
         }
     }
+#endif
     barrier();
 }
 #endif