From f8e144b23b79369cda26f42db451cbafef811f18 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Fri, 27 Mar 2026 16:14:49 -1000
Subject: [PATCH] Use init_array_from helper for optimal codegen

Uses memcpy for trivially copyable types, element-wise copy otherwise.
ESPHOME_DEBUG_ASSERT catches size mismatches in integration tests.
---
 esphome/components/sensor/filter.h |  6 +-----
 esphome/core/helpers.h             | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/esphome/components/sensor/filter.h b/esphome/components/sensor/filter.h
index f7838078b7..a52cbbafd4 100644
--- a/esphome/components/sensor/filter.h
+++ b/esphome/components/sensor/filter.h
@@ -497,11 +497,7 @@ optional<float> calibrate_linear_compute(const std::array<float, 3> *functions,
 template<size_t N> class CalibrateLinearFilter : public Filter {
  public:
   explicit CalibrateLinearFilter(std::initializer_list<std::array<float, 3>> linear_functions) {
-    ESPHOME_DEBUG_ASSERT(linear_functions.size() == N);
-    size_t i = 0;
-    for (const auto &f : linear_functions) {
-      this->linear_functions_[i++] = f;
-    }
+    init_array_from(this->linear_functions_, linear_functions);
   }
   optional<float> new_value(float value) override {
     return calibrate_linear_compute(this->linear_functions_.data(), N, value);
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 82c6b3833c..51feaa57c5 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -497,6 +497,21 @@ template<typename T, size_t MAX_CAPACITY = std::numeric_limits<uint16_t>::max()>
   index_type capacity_{0};
 };
 
+/// Initialize a std::array from an initializer_list. Uses memcpy for trivially copyable types (optimal codegen),
+/// falls back to element-wise copy for non-trivially copyable types (e.g. TemplatableValue).
+/// N is set by code generation; ESPHOME_DEBUG_ASSERT catches mismatches in debug/integration tests.
+template<typename T, size_t N> inline void init_array_from(std::array<T, N> &dest, std::initializer_list<T> src) {
+  ESPHOME_DEBUG_ASSERT(src.size() == N);
+  if constexpr (std::is_trivially_copyable_v<T>) {
+    __builtin_memcpy(dest.data(), src.begin(), N * sizeof(T));
+  } else {
+    size_t i = 0;
+    for (const auto &v : src) {
+      dest[i++] = v;
+    }
+  }
+}
+
 /// Fixed-capacity vector - allocates once at runtime, never reallocates
 /// This avoids std::vector template overhead (_M_realloc_insert, _M_default_append)
 /// when size is known at initialization but not at compile time