Add 1MB temp allocator for executor

Differential Revision: D80578578

Pull Request resolved: pytorch#13533

Author: zonglinpeng

backends/cadence/fusion_g3/operators/op_native_layer_norm.cpp

@@ -221,12 +221,15 @@ std::tuple<Tensor&, Tensor&, Tensor&> native_layer_norm_out(
       num_elm *= normalized_shape[i];
     }
 
+    constexpr size_t kAlignment =
+        16; // 16-byte alignment for vectorized operations
+
     float* weight_data;
     if (weight.has_value()) {
       weight_data = weight.value().mutable_data_ptr<float>();
     } else {
       executorch::runtime::Result<void*> temp_mem_weight =
-          ctx.allocate_temp(num_elm * sizeof(float));
+          ctx.allocate_temp(num_elm * sizeof(float), kAlignment);
       weight_data = (float*)(temp_mem_weight.get());
 
       for (int i = 0; i < num_elm; i++) {
@@ -238,7 +241,7 @@ std::tuple<Tensor&, Tensor&, Tensor&> native_layer_norm_out(
       bias_data = bias.value().mutable_data_ptr<float>();
     } else {
       executorch::runtime::Result<void*> temp_mem_bias =
-          ctx.allocate_temp(num_elm * sizeof(float));
+          ctx.allocate_temp(num_elm * sizeof(float), kAlignment);
       bias_data = (float*)(temp_mem_bias.get());
 
       for (int i = 0; i < num_elm; i++) {

backends/cadence/hifi/kernels/kernels.cpp

@@ -21,11 +21,19 @@ memcpy(void* dst, const void* src, size_t num_bytes) {
 }
 
 void* allocate_temp_memory(KernelRuntimeContext& ctx, size_t size) {
-  ET_LOG(Info, "Attempting to allocate %zu bytes of temp memory", size);
-  Result<void*> temp_mem_res = ctx.allocate_temp(size);
+  constexpr size_t kAlignment =
+      16; // 16-byte alignment for vectorized operations
+  ET_LOG(
+      Info,
+      "Attempting to allocate %zu bytes of temp memory (16-byte aligned)",
+      size);
+  Result<void*> temp_mem_res = ctx.allocate_temp(size, kAlignment);
   if (temp_mem_res.ok()) {
     void* ptr = temp_mem_res.get();
-    ET_LOG(Info, "Successfully allocated temp memory at %p", ptr);
+    ET_LOG(
+        Info,
+        "Successfully allocated temp memory at %p (16-byte aligned)",
+        ptr);
     return ptr;
   } else {
     ET_LOG(