Runtime Performance Profiling

/* Profile individual functions inside Dem_MainFunction */
/* Requires ETM (Embedded Trace Macrocell) hardware */

TRACE.METHOD ETM
TRACE.ON

/* Set profiling scope to Dem_MainFunction */
PERF.GATE Dem_MainFunction
Go
WAIT 1.s
PERF.LISTFUNC  /* sorted by CPU time */

/* Example output:
   Function                    | Calls | Total (us) | Self (us) | %
   Dem_MainFunction            |   100 |  5000      |    200    | 4%
   Dem_EventDebounce           |  3200 |  2000      |   2000    | 40%  ← hot
   Dem_DtcStorageHandling      |   100 |  1500      |   1500    | 30%
   Dem_ClearDTCFilter          |    10 |   800      |    800    | 16%

   Finding: Dem_EventDebounce is called 32x per Dem_MainFunction cycle
   Action: increase DemDebounceCounterBasedStepSize to skip unnecessary calls */

#!/bin/bash
# Verify COM signal getters compile to direct struct access, not function calls
arm-none-eabi-objdump -d ECU_EPS.elf | grep -A5 "Com_GetSignal_VehicleSpeed"

# BAD: function call overhead (~10 cycles on Cortex-M7)
# 0800A100: push {lr}
# 0800A102: bl   0800B000 
# 0800A106: pop  {pc}

# GOOD: inlined direct memory access (~3 cycles)
# 0800A100: ldr  r0, [r4, #0x14]  ; direct struct field access
# 0800A102: uxth r0, r0            ; zero-extend uint16

# If not inlined: add INLINE keyword to Com_GetSignal wrapper in Com_Cfg.h
# Or enable -O2 and verify __attribute__((always_inline)) is present in generated header 

/* Place frequently-accessed COM signal buffers in same cache line */
/* Cortex-R5 L1 D-cache: 32-byte cache lines */

/* BEFORE: signal buffers scattered in .bss — multiple cache misses per task */
uint16 Com_Sig_VehicleSpeed;   /* .bss offset 0x100 */
uint16 Com_Sig_EngineRPM;      /* .bss offset 0x240 — different cache line */
uint16 Com_Sig_GearPosition;   /* .bss offset 0x380 — different cache line */

/* AFTER: co-locate in linker script section */
/* In linker scatter file: */
/* .com_hot_signals 0x20001000 : { *(.com_hot_signals) } */

/* In Com_Cfg.h: */
uint16 Com_Sig_VehicleSpeed   __attribute__((section(".com_hot_signals")));
uint16 Com_Sig_EngineRPM      __attribute__((section(".com_hot_signals")));
uint16 Com_Sig_GearPosition   __attribute__((section(".com_hot_signals")));
/* All three fit in one 32-byte cache line → 3 signals for price of 1 cache miss */