CCS/MSP-EXP432P4111: #2623-D (ULP 5.4) Detected an assignment to a type with size less than int. To avoid unnecessary sign extension, use int-sized types for local varaibles and convert to smaller types for static storage.

Peter Vittali

Expert 2015 points

Part Number: MSP-EXP432P4111

Tool/software: Code Composer Studio

on Linux 16.04 and CCS Version: 8.0.0.00016, MSP-EXP432P4111

The following code give a ULP 5.4 warning where count is incremented:

#include "msp.h"

uint16_t testResult = 0;
void main(void)
{
    uint8_t count = 0;
    WDT_A->CTL = WDT_A_CTL_PW | WDT_A_CTL_HOLD;        // stop watchdog timer

    while (1)
    {
        count++;
        if (count == 3)
        {
            testResult = 1;
        }
    }
}

What does this mean ? How could I improve the code to honour the advice ?

Is this the same issue as this ?

Regards

Peter

over 8 years ago

0 Bruce McKenney over 8 years ago

Guru 102365 points

Yes, it's pretty much the same as in the other article. You can:
1) Change "count" to be a "uint32_t" (since the Cortex-M4 is 32-bit) or
2) Disable ULP 5.4 ("Show Build settings/ULP").

0 Peter Vittali over 8 years ago in reply to Bruce McKenney

Expert 2015 points

I have compared the dissambly.

This is the result when the warning is shown (uint8):

And this is with a unit32_t type that suppresses the warning:

Basically, the opcodes

ldr and str ( unit32_t) are replaced with ldrb and strb. In either case, 2 cycles are required, with possible optimization to one cycle.

So does the warning make sense in this case ?

Regards

Peter

0 Bruce McKenney over 8 years ago in reply to Peter Vittali

Guru 102365 points

That would be a question for the ULP Advisor designers.

0 George Mock over 7 years ago

TI__Guru**** 253010 points

Peter Vittali said:
The following code give a ULP 5.4 warning where count is incremented:

To understand why this happens, consider that the expression count++, when fully expanded to show all the implicit type conversions, is ...

count = (uint8_t)((int)count + 1);

The addition operation is only defined for int, so count is converted to int. Next, the addition occurs. Next, the result is converted to uint8_t. Finally, the result is assigned to count. It is the conversion from int to uint8_t which triggers the ULP 5.4 diagnostic.

There are a few ways to fix this. I recommend changing the type of count from uint8_t to uint_fast8_t. This is another type defined in stdint.h. It is the fastest type which has at least 8 bits. For ARM, this is a 32-bit unsigned int. 32-bits because that is the size of a register. This change avoids the implicit conversions, and the ULP diagnostic.

Thanks and regards,

-George

0 Peter Vittali over 7 years ago in reply to George Mock

Expert 2015 points

Very good, thank you !

Regards Peter

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CCS/MSP-EXP432P4111: #2623-D (ULP 5.4) Detected an assignment to a type with size less than int. To avoid unnecessary sign extension, use int-sized types for local varaibles and convert to smaller types for static storage.