STM32F0 benchmarks

[Delsian]

Pretty strange results for more than one stepper, but I've run tests few times and results the same.

[KevinOConnor]

Thanks.

FYI, the reason for the poor performance (relative to the similar SAMD21 chip) is due to the lack of -fwhole-program. gcc just doesn't do a good job of inlining without that flag.

-Kevin

[Delsian]

@KevinOConnor Unfortunately in my GCC version I can use either -fwhole-program or -fno-use-linker-plugin, but not both :(

[KevinOConnor]

Can you describe the problem you are seeing? It compiles fine for me with the following changes:

diff --git a/src/stm32f0/Makefile b/src/stm32f0/Makefile
index 16136b52..093be66f 100644
--- a/src/stm32f0/Makefile
+++ b/src/stm32f0/Makefile
@@ -9,9 +9,6 @@ dirs-y += src/stm32f0 src/generic
 dirs-y += lib/cmsis-stm32f0/source
 dirs-y += lib/hal-stm32f0/source
 
-CFLAGS = -I$(OUT) -Isrc -I$(OUT)board-generic/ -std=gnu11 -O2 -MD \
-    -Wall -Wold-style-definition $(call cc-option,$(CC),-Wtype-limits,) \
-    -ffunction-sections -fdata-sections
 CFLAGS += -flto -fno-use-linker-plugin
 CFLAGS += -mthumb -mcpu=cortex-m0 -g3
 CFLAGS += -Ilib/cmsis-core -Iout/board
@@ -60,7 +57,7 @@ $(OUT)klipper.bin: $(OUT)klipper.elf
 $(OUT)klipper.hex: $(OUT)klipper.elf
        @echo "  Creating hex file $@"
        $(Q)$(OBJCOPY) -O ihex $< $@
-       
+
 flash: $(OUT)klipper.hex
        @echo "  Flashing hex file $<"
        $(Q)$(STLINK) --format ihex --reset write $<
diff --git a/src/stm32f0/can.c b/src/stm32f0/can.c
index 6ce9aad4..cc0c0bf1 100644
--- a/src/stm32f0/can.c
+++ b/src/stm32f0/can.c
@@ -149,7 +149,7 @@ void HAL_CAN_ErrorCallback(CAN_HandleTypeDef *h)
   * @brief This function handles HDMI-CEC and CAN global interrupts /
   *  HDMI-CEC wake-up interrupt through EXTI line 27.
   */
-void CEC_CAN_IRQHandler(void)
+void __visible CEC_CAN_IRQHandler(void)
 {
     HAL_CAN_IRQHandler(&hcan);
 }
diff --git a/src/stm32f0/main.c b/src/stm32f0/main.c
index 89d8a6e5..da1f129c 100644
--- a/src/stm32f0/main.c
+++ b/src/stm32f0/main.c
@@ -149,7 +149,7 @@ void HAL_MspInit(void)
  * on Cortex-M0 chips
  ****************************************************************/
 
-void hard_fault_handler_c(unsigned long *hardfault_args){
+void __visible hard_fault_handler_c(unsigned long *hardfault_args){
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
     volatile unsigned long stacked_r0 ;
diff --git a/src/stm32f0/serial.c b/src/stm32f0/serial.c
index 103a0d70..7c3ba892 100644
--- a/src/stm32f0/serial.c
+++ b/src/stm32f0/serial.c
@@ -15,7 +15,7 @@
 UART_HandleTypeDef huart2;
 static uint8_t rxbuf, txbuf;
 
-void USART2_IRQHandler(void)
+void __visible USART2_IRQHandler(void)
 {
   HAL_UART_IRQHandler(&huart2);
 }
diff --git a/src/stm32f0/timer.c b/src/stm32f0/timer.c
index 0b285d4e..f51e69ba 100644
--- a/src/stm32f0/timer.c
+++ b/src/stm32f0/timer.c
@@ -77,7 +77,7 @@ SysTick_Handler(void)
     irq_enable();
 }
 
-void TIM2_IRQHandler(void)
+void __visible TIM2_IRQHandler(void)
 {
     if(TIM2->SR & TIM_SR_UIF) {
         TIM2->SR &= ~TIM_SR_UIF; // clear UIF flag

We use -fwhole-program on a number of different gcc versions and on a number of different ARM targets, so I think it would be worthwhile to track down what the root cause of the problem is.

-Kevin

[Delsian]

@KevinOConnor Yes, you are right, I forgot about __visible
This variant should work better.

[KevinOConnor]

BTW, is the code in lib/cmsis-stm32f0/ the pristine code from st? I noticed that only startup_stm32f042x6.s has a reference to hard_fault_handler_c - that's certainly odd.

-Kevin

[Delsian]

@KevinOConnor yes, I put this change for debugging purposes. Probably we can drop this change as everything working, I hope we don't need huge code changes in future.

[KevinOConnor]

I don't have the original st code, so I can't remove the changes. I'd like the code in the lib/ directory to have accurate documentation on where the code originates from. So, please submit a pull request returning the code in the lib/ directory to the pristine code from st, or update the lib/README with a list of all the changes in the code (for example, take a look at how the changes to the lib/sam4e/ directory are documented).

Thanks,
-Kevin