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no_stm option in ARMCL compilers

QJ Wang
Guru**** 197016 points

Hi George,

Because of the HW bug on TMS570 revA/B, any write to external memory using STMxx instructions will result in a failure on a subsequent write operation. The HW bug has been fixed on revC silicon. 

TI ARMCL compiler 5.1.3 and later versions support a "--no_stm" compile option that prevents generation of STMxx instructions for any writes to memory. One of my customers likes to know:

1. Is this option still supported by the latest ARMCL compilers? for exemple TI v20.2.x. After I added --no_stm option to compiler built flags, I got this warning message. Is this message expected?

2. When --no_stm is used, "no_stm_memcpy" and "no_stm_memset" will be called for memcpy and memset C/C++ functions. Does this mean that only memcpy and memset functions generate STMxx instructions? Is STMxx generated by any other C/C++ functions?

3. The customer said they saw issue when using LDMxx instructions. Is there any way to prevent the ARMCL compiler from generating LDMxx instructions?

  • 0
    TI__Guru**** 249640 points
    QJ Wang said:
    Is this option still supported by the latest ARMCL compilers?

    Yes

    QJ Wang said:
    After I added --no_stm option to compiler built flags, I got this warning message. Is this message expected?

    The warning issued by CCS is expected.

    QJ Wang said:
    When --no_stm is used, "no_stm_memcpy" and "no_stm_memset" will be called for memcpy and memset C/C++ functions. Does this mean that only memcpy and memset functions generate STMxx instructions?

    No

    QJ Wang said:
    Is STMxx generated by any other C/C++ functions?

    Yes.  But only to preserve registers on the stack.  If the stack is allocated to internal memory, there will be no problems.

    All of that said, it is my understanding that a silicon errata document has all of these details.  I am unable to find that document.  So while I am confident all the information in this post is accurate, I have not confirmed it.

    QJ Wang said:
    Is there any way to prevent the ARMCL compiler from generating LDMxx instructions?

    No

    Thanks and regards,

    -George

  • +1 in reply to George Mock
    TI__Guru**** 197016 points

    Hi George,

    Thanks for quick response. All my questions have been answered!