vulkan: remove PV matrix, helps with register usage

Author: jeffbolznv

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

@@ -276,27 +276,22 @@ void main() {
             Lf[r] = eMf[r]*Lf[r] + rowsumf[r];
         }
 
-        uint32_t v_offset = (iv2*p.nb22 + iv3*p.nb23) / 2;
-
-        vec4 PVf[Br][D_per_thread / 4];
         [[unroll]] for (uint32_t d = 0; d < D_per_thread / 4; ++d) {
             [[unroll]] for (uint32_t r = 0; r < Br; ++r) {
-                PVf[r][d] = vec4(0.0);
+                Of[r][d] = eMf[r] * Of[r][d];
             }
         }
+
+        uint32_t v_offset = (iv2*p.nb22 + iv3*p.nb23) / 2;
+
         [[unroll]] for (uint32_t c = 0; c < cols_per_thread; ++c) {
             [[unroll]] for (uint32_t d = 0; d < D_per_thread / 4; ++d) {
                 vec4 Vf = vec4(data_vv4[v_offset / 4 + (j * Bc + c * cols_per_iter + col_tid) * v_stride / 4 + d * D_split + d_tid]);
                 [[unroll]] for (uint32_t r = 0; r < Br; ++r) {
-                    PVf[r][d] += Pf[r][c] * Vf;
+                    Of[r][d] += Pf[r][c] * Vf;
                 }
             }
         }
-        [[unroll]] for (uint32_t d = 0; d < D_per_thread / 4; ++d) {
-            [[unroll]] for (uint32_t r = 0; r < Br; ++r) {
-                Of[r][d] = eMf[r] * Of[r][d] + PVf[r][d];
-            }
-        }
 
         barrier();
     }