esp_timer: alias esp_timer_get_time

alias esp_timer_get_time to improve performance

components/esp_timer/private_include/esp_timer_impl.h

@@ -73,7 +73,7 @@ void esp_timer_impl_advance(int64_t time_us);
  * @brief Get time, in microseconds, since esp_timer_impl_init was called
  * @return timestamp in microseconds
  */
-uint64_t esp_timer_impl_get_time(void);
+int64_t esp_timer_impl_get_time(void);
 
 /**
  * @brief Get minimal timer period, in microseconds

components/esp_timer/src/esp_timer.c

@@ -278,7 +278,7 @@ static void timer_process_alarm(esp_timer_dispatch_t dispatch_method)
     (void) dispatch_method;
 
     timer_list_lock();
-    uint64_t now = esp_timer_impl_get_time();
+    int64_t now = esp_timer_impl_get_time();
     esp_timer_handle_t it = LIST_FIRST(&s_timers);
     while (it != NULL &&
             it->alarm < now) {
@@ -502,8 +502,3 @@ int64_t IRAM_ATTR esp_timer_get_next_alarm(void)
     timer_list_unlock();
     return next_alarm;
 }
-
-int64_t IRAM_ATTR esp_timer_get_time(void)
-{
-    return (int64_t) esp_timer_impl_get_time();
-}

components/esp_timer/src/esp_timer_impl_frc_legacy.c

@@ -176,7 +176,7 @@ void esp_timer_impl_unlock(void)
     portEXIT_CRITICAL(&s_time_update_lock);
 }
 
-uint64_t IRAM_ATTR esp_timer_impl_get_time(void)
+int64_t IRAM_ATTR esp_timer_impl_get_time(void)
 {
     uint32_t timer_val;
     uint64_t time_base;
@@ -209,6 +209,8 @@ uint64_t IRAM_ATTR esp_timer_impl_get_time(void)
     return result;
 }
 
+int64_t esp_timer_get_time(void) __attribute__((alias("esp_timer_impl_get_time")));
+
 void IRAM_ATTR esp_timer_impl_set_alarm(uint64_t timestamp)
 {
     portENTER_CRITICAL_SAFE(&s_time_update_lock);

components/esp_timer/src/esp_timer_impl_lac.c

@@ -144,11 +144,13 @@ uint64_t IRAM_ATTR esp_timer_impl_get_counter_reg(void)
     return result.val;
 }
 
-uint64_t IRAM_ATTR esp_timer_impl_get_time(void)
+int64_t IRAM_ATTR esp_timer_impl_get_time(void)
 {
     return esp_timer_impl_get_counter_reg() / TICKS_PER_US;
 }
 
+int64_t esp_timer_get_time(void) __attribute__((alias("esp_timer_impl_get_time")));
+
 void IRAM_ATTR esp_timer_impl_set_alarm(uint64_t timestamp)
 {
     portENTER_CRITICAL_SAFE(&s_time_update_lock);

components/esp_timer/src/esp_timer_impl_systimer.c

@@ -63,11 +63,14 @@ uint64_t IRAM_ATTR esp_timer_impl_get_counter_reg(void)
     return systimer_hal_get_counter_value(SYSTIMER_COUNTER_0);
 }
 
-uint64_t IRAM_ATTR esp_timer_impl_get_time(void)
+int64_t IRAM_ATTR esp_timer_impl_get_time(void)
 {
     return systimer_hal_get_time(SYSTIMER_COUNTER_0);
 }
 
+// Xtensa architecture doesn't have tail call optimization, using alias here can improve performance somehow
+int64_t esp_timer_get_time(void) __attribute__((alias("esp_timer_impl_get_time")));
+
 void IRAM_ATTR esp_timer_impl_set_alarm(uint64_t timestamp)
 {
     portENTER_CRITICAL_SAFE(&s_time_update_lock);

components/esp_timer/test/test_esp_timer.c

@@ -113,8 +113,8 @@ TEST_CASE("esp_timer_impl_set_alarm stress test", "[esp_timer]")
     {
         SemaphoreHandle_t done = (SemaphoreHandle_t) arg;
 
-        uint64_t start = esp_timer_impl_get_time();
-        uint64_t now = start;
+        int64_t start = esp_timer_impl_get_time();
+        int64_t now = start;
         int count = 0;
         const int delays[] = {50, 5000, 10000000};
         const int delays_count = sizeof(delays)/sizeof(delays[0]);