如何进行XC32编译器的优化

我面临的问题是XC32编译器的优化。每当我写一个函数从寄存器读出某些东西时，XC32就优化（读取：移除）保存返回值的变量。范围选择输入u8pinstatus=(uint8_t)SYS_PORTS_BIT_REREAD(_SFR_BIT_RERERE_B VREG(索引)+((通道-通道-信道_信道_READ_BVREBVREG(索引)+((索引)+((信道)+((信道)+((信道)信道((信道-信道-信道-信道-信道_REREAD_BVVVRE)+(((索引)+(((索引)+((信道)+((信道)+((信道)+((信道)+((信道)+((信道)(((((信道)通道-信道)信道注意，它是一个内联函数。现在，当我将优化级别设置为1，XC32移除“u8pinstatus”变量并总是返回0。但如果我声明“u8pinstatus”为“volatile”，一切正常（这是预期的），但是随后我需要声明所有变量为volatile。因为我的包装器函数总是返回0。这不是一个好方法。我在配置编译器设置或其他方面做了什么错误或问题吗？**附加信息：**汇编代码与优化*：UIT88T U8TnIIdioRead选择（无效）！{0x9D0AA8C：Addiu SP，SP，- 24 0x9D00 AA90:SW RA，20（SP）！UIT88T U8PIN状态＝0；！//读取引脚分配给范围选择输入！u8pinstatus=(uint8_t)SYS_PORTS_PinRead(PORTS_ID_0, 0x9D00AA94: ADDU A0,零,零0x9D00AA98: ADDIU A1,零, 3 0x9D00AA9C: JAL SYS_PORTS_PinRead 0x9D00AAA0: ADDIU A2,零, 8!RangeEx选择端口，RangeEx选择StPin！返回U8PIN状态；！}0x9D0AAA4:LW RA，20（SP）0x9D00 AAA8:JR RA 0x9DAAAAC: Audiu SP，SP，24 *汇编代码没有优化*：UIT88T U8TnIIdioRead选择（无效）！{0x9D0F98:Audiu SP，SP，-0x99D00 F99 C:SW RA，28（SP）0x9D00 F9A0:SW S8，24（SP）0x9D00 F9A4：ADUU S8，SP，0！UIT88T U8PoNoSt= 0；0x9D00 F9A8: SB零，16（S8）！！//读取引脚分配给范围选择输入！8pinstatus=(uint8_t)SYS_PORTS_Pin读取(PORTS_ID_0，0x9D00F9AC0x9D00F9AC00X9D00F9F9ACADDUA0：ADDU A0，零，零，零，零，3x9D00F9B0：ADDIU A1，零，3x9D00F9B4：ADDIU A2，零，8 0x9D00D00F9B8X9D00D00DD00F9B8：JAL SYS_PORTS_读0x9D00F9DD00F9BC：JALSYXXXX9DDD00F9分针针读0X9DD00F9D00F9)RangeEx选择端口，RangeEx选择StPin！返回U8PIN状态；0x9D00 F9C4：LBU V0，16（S8）！}0x9D00F9C8：ADDU SP，S8，零0x9D00F9CC：LW RA，28(SP)0x9D00F9D0：LW S8，24(SP)0x9D00F9D4：ADDIU SP，SP，320x9D00F9D8：JR RA 0x9D00F9DC：NOP



      以下为原文

    I am facing a problem with XC32 compiler's optimization. Whenever I write a function to read something from register, XC32 optimizes (read: Removes) the variable which holds the return value.
I have a wrapper function which reads a perticular pin of perticular port:
    uint8_t u8INT_DIO_ReadRangeSelect(void)
    {
        uint8_t u8pinstatus = 0;
        
        // Read pin assigned to Range Select input
        u8pinstatus = (uint8_t) SYS_PORTS_PinRead(PORTS_ID_0,
                RANGE_SELECT_PORT, RANGE_SELECT_PIN);
   
        return u8pinstatus;
    }
Here `SYS_PORTS_PinRead` is a HARMony generated code and it just reads the port pin.
Code for that is:
`    return( _SFR_BIT_READ( _PORTS_READ_B_VREG(index) + ((channel-1) * 0x40), bitPos ) );`
Note that, it's an inline function.
Now, when I set Optimization level to 1, XC32 removes `u8pinstatus` variable and always returns 0.
But if I declare `u8pinstatus` as `volatile`, everything works fine (which was expected).
But then I need to declare all the variables volatile because all my wrapper functions are always returning 0. That's not a good way.
am I doing something wrong or problem in configuring compiler settings or anything else?

**Additional Info:**
*Assembly code with optimization*:
    !uint8_t u8INT_DIO_ReadRangeSelect(void)
    !{
    0x9D00AA8C: ADDIU SP, SP, -24
    0x9D00AA90: SW RA, 20(SP)
    !    uint8_t u8pinstatus = 0;
    !   
    !    // Read pin assigned to Range Select input
    !    u8pinstatus = (uint8_t) SYS_PORTS_PinRead(PORTS_ID_0,
    0x9D00AA94: ADDU A0, ZERO, ZERO
    0x9D00AA98: ADDIU A1, ZERO, 3
    0x9D00AA9C: JAL SYS_PORTS_PinRead
    0x9D00AAA0: ADDIU A2, ZERO, 8
    !            RANGE_SELECT_PORT, RANGE_SELECT_PIN);
    !    return u8pinstatus;
    !}
    0x9D00AAA4: LW RA, 20(SP)
    0x9D00AAA8: JR RA
    0x9D00AAAC: ADDIU SP, SP, 24
*Assembly code without optimization*:

    !uint8_t u8INT_DIO_ReadRangeSelect(void)
    !{
    0x9D00F998: ADDIU SP, SP, -32
    0x9D00F99C: SW RA, 28(SP)
    0x9D00F9A0: SW S8, 24(SP)
    0x9D00F9A4: ADDU S8, SP, ZERO
    !    uint8_t u8pinstatus = 0;
    0x9D00F9A8: SB ZERO, 16(S8)
    !   
    !    // Read pin assigned to Range Select input
    !    u8pinstatus = (uint8_t) SYS_PORTS_PinRead(PORTS_ID_0,
    0x9D00F9AC: ADDU A0, ZERO, ZERO
    0x9D00F9B0: ADDIU A1, ZERO, 3
    0x9D00F9B4: ADDIU A2, ZERO, 8
    0x9D00F9B8: JAL SYS_PORTS_PinRead
    0x9D00F9BC: NOP
    0x9D00F9C0: SB V0, 16(S8)
    !            RANGE_SELECT_PORT, RANGE_SELECT_PIN);
    !    return u8pinstatus;
    0x9D00F9C4: LBU V0, 16(S8)
    !}
    0x9D00F9C8: ADDU SP, S8, ZERO
    0x9D00F9CC: LW RA, 28(SP)
    0x9D00F9D0: LW S8, 24(SP)
    0x9D00F9D4: ADDIU SP, SP, 32
    0x9D00F9D8: JR RA
    0x9D00F9DC: NOP