Optimization Assembly Problems

Hello everyone,

I am currently having an issue with some code I have that seems to vary based on optimization:

In CommBuff ISR:

if (commData == 0x61)   /* 0x61 = 'a' */
{
        if(DAC1DifVoltn==1)
        {
                DigPressure1 = DiffPressure1;  // Enters this section, problem here
        }
        else
        {
                DigPressure1 = Pressure1>>3;
        }
        COMBUF = DigPressure1>>8;
}
else if (commData == 0x62)      /* 0x62 = 'b' */
{
        COMBUF = DigPressure1;
}

Currently, DAC1DifVoltn is set to 1. When the COMBUF register gets a 0x61, it updates DigPressure1 and puts out the MSB on the COMBUF. When it receives 0x62, it sends out the LSB bits.

The problem I'm having is with the line:

DigPressure1 = DiffPressure1;

DiffPressure1 is set to 0x0FF8. When optimization is set to 4-8, DigPressure1 is set to 0x0097. When it's set to 3, it gets 0x0F97. When it's set to 2-0, it gets the correct value (0x0FF8). Realistically, this has to do with the way my code is written rather than it being an assembly issue but I can't seem to see a better way to handle this.

Does anyone have any explanations as to what I can do? If you need me to post the assembly code, I can do that as well. Any help would be appreciated. Thanks!