如何控制C编译器优化的内容？
时间：2023-02-25 03:00:00
我正在使用Silicon Labs IDE和SDCC编译器在C语言中为嵌入式设备编写固件。基于8051系列的设备架构。如下所示。该功能用于设置MCU上端口驱动步进电机。它被中断处理程序调用。 big switch语句只是将端口设置为下一步电机步骤的正确值。检查霍尔效应传感器输入和移动的多个步骤，以检测电机是否已停止。问题是，由于某种原因，它看起来像第二个IF句子似乎总是优化的。假如我试着HandleStallEvent()调用时设置断点，IDE向我展示一条消息，指出此行号无地址关联。在阅读汇编时，我不太擅长讲述它在做什么，但我已经从下面开始了asm片段粘贴在输出中。任何帮助都助。
void OperateStepper(void)
{
//static bit LastHomeMagState = HomeSensor;
static bit LastPosMagState = PosSensor;
if(PulseMotor)
{
if(MoveDirection == 1) // Go clockwise
{
switch(STEPPER_POSITION)
{
case 'A':
STEPPER_POSITION = 'B';
P1 = 0xFD;
break;
case 'B':
STEPPER_POSITION = 'C';
P1 = 0xFF;
break;
case 'C':
STEPPER_POSITION = 'D';
P1 = 0xFE;
break;
case 'D':
STEPPER_POSITION = 'A';
P1 = 0xFC;
break;
default:
STEPPER_POSITION = 'A';
P1 = 0xFC;
} //end switch
}
else // Go CounterClockwise
{
switch(STEPPER_POSITION)
{
case 'A':
STEPPER_POSITION = 'D';
P1 = 0xFE;
break;
case 'B':
STEPPER_POSITION = 'A';
P1 = 0xFC;
break;
case 'C':
STEPPER_POSITION = 'B';
P1 = 0xFD;
break;
case 'D':
STEPPER_POSITION = 'C';
P1 = 0xFF;
break;
default:
STEPPER_POSITION = 'A';
P1 = 0xFE;
} //end switch
} //end else
MotorSteps ;
StallDetector ;
if(PosSensor != LastPosMagState)
{
StallDetector = 0;
LastPosMagState = PosSensor;
}
else
{
if (PosSensor == ON)
{
if (StallDetector > (MagnetSize 20))
{
HandleStallEvent();
}
}
else if (PosSensor == OFF)
{
if (StallDetector > (GapSize 20))
{
HandleStallEvent();
}
}
}
} //end if PulseMotor
}
...以及函数底部asm输出...
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:653: if(PosSensor != LastPosMagState)
mov c,_P1_4
jb _OperateStepper_LastPosMagState_1_1,00158$
cpl c
00158$:
jc 00126$
C$MotionControl.c$655$3$7 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:655: StallDetector = 0;
clr a
mov _StallDetector,a
mov (_StallDetector 1),a
C$MotionControl.c$657$3$7 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:657: LastPosMagState = PosSensor;
mov c,_P1_4
mov _OperateStepper_LastPosMagState_1_1,c
ret
00126$:
C$MotionControl.c$661$2$8 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:661: if (PosSensor == ON)
jb _P1_4,00123$
C$MotionControl.c$663$4$9 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:663: if (StallDetector > (MagnetSize 20))
mov a,_MagnetSize
mov r2,a
rlc a
subb a,acc
mov r3,a
mov a,#0x14
add a,r2
mov r2,a
clr a
addc a,r3
mov r3,a
clr c
mov a,r2
subb a,_StallDetector
mov a,r3
subb a,(_StallDetector 1)
jnc 00130$
C$MotionControl.c$665$5$10 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:665: HandleStallEvent();
ljmp _HandleStallEvent
00123$:
C$MotionControl.c$668$2$8 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:668: else if (PosSensor == OFF)
jnb _P1_4,00130$
C$MotionControl.c$670$4$11 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MotionControl.c:670: if (StallDetector > (GapSize 20))
mov a,#0x14
add a,_GapSize
mov r2,a
clr a
addc a,(_GapSize 1)
mov r3,a
clr c
mov a,r2
subb a,_StallDetector
mov a,r3
subb a,(_StallDetector 1)
jnc 00130$
C$MotionControl.c$672$5$12 ==.
; C:SiLabsOptec ProgramsHSFW_HID_SDCC_2MtionControl.c:672: HandleStallEvent();
C$MotionControl.c$678$2$1 ==.
XG$OperateStepper$0$0 ==.
ljmp _HandleStallEvent
00130$:
ret
在我看来，编译器并没有从asm的外观中优化掉第二个if语句但是如果是这样的话为什么IDE不允许我这样设置断点呢？也许这只是一个愚蠢的IDE！
