metal : assert shared memory padding (#27951)

* metal : assert shared memory padding

* cont : add ref

ggml/src/ggml-metal/ggml-metal-device.cpp

@@ -593,7 +593,7 @@ ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_ssm_scan(ggml_me
     // - sgptg floats for shared_x_dt (nsg)
     // - sgptg floats for shared_dA (nsg)
     // Total: nsg * (32 + 2) floats
-    res.smem = (32 + 2)*sizeof(float)*nsg;
+    res.smem = GGML_PAD((32 + 2)*sizeof(float)*nsg, 16);
 
     return res;
 }
@@ -1029,6 +1029,7 @@ ggml_metal_pipeline_with_params ggml_metal_library_get_pipeline_mul_mm_id_map0(g
     }
 
     res.smem = (size_t) ne02*ne20*sizeof(uint16_t);
+    res.smem = GGML_PAD(res.smem, 16);
 
     return res;
 }

ggml/src/ggml-metal/ggml-metal-device.m

@@ -800,6 +800,9 @@ void ggml_metal_encoder_set_buffer(ggml_metal_encoder_t encoder, struct ggml_met
 }
 
 void ggml_metal_encoder_set_threadgroup_memory_size(ggml_metal_encoder_t encoder, size_t size, int idx) {
+    // ref: https://developer.apple.com/documentation/metal/mtlcomputecommandencoder/setthreadgroupmemorylength(_:index:)
+    GGML_ASSERT(size % 16 == 0);
+
     [encoder->obj setThreadgroupMemoryLength:size atIndex:idx];
 }
 

ggml/src/ggml-metal/ggml-metal-ops.cpp

@@ -948,7 +948,7 @@ int ggml_metal_op_sum(ggml_metal_op_t ctx, int idx) {
     ggml_metal_encoder_set_buffer  (enc, ggml_metal_get_buffer_id(op->src[0]), 1);
     ggml_metal_encoder_set_buffer  (enc, ggml_metal_get_buffer_id(op),         2);
 
-    ggml_metal_encoder_set_threadgroup_memory_size(enc, nsg * sizeof(float), 0);
+    ggml_metal_encoder_set_threadgroup_memory_size(enc, GGML_PAD(nsg * sizeof(float), 16), 0);
 
     ggml_metal_encoder_dispatch_threadgroups(enc, 1, 1, 1, nth, 1, 1);