ARM-CGT: Use of -mllvm -align-all-functions=2 compiler option

Hi Dhaval,

Can you please share a bit more information?

• What version of the AM243x MCU+SDK are you using?
• What version of the TI CLANG compiler?
• Which example from the SDK?
• Can you show exactly how you're adding the compiler option for the make file and CCS builds?

Regards,
Frank

Hi

Frank Livingston said:

What version of the AM243x MCU+SDK are you using?

08_02_00_12

Frank Livingston said:

What version of the TI CLANG compiler?

1.3.0.LTS

Frank Livingston said:

Which example from the SDK?

examples\industrial_comms\ethernetip_adapter_demo

Frank Livingston said:

Can you show exactly how you're adding the compiler option for the make file and CCS builds?

• CCS : Adding this option in Project Properties -> Arm Compiler -> Edit Flags
• Makefile : Adding the flags inside "CFLAGS_common :=" in makefile

Regards
Dhaval Khandla

Dhaval Khandla said:

CCS : Adding this option in Project Properties -> Arm Compiler -> Edit Flags

With CCS 11.1 and TI CLANG 1.3.0.LTS I tried adding -mllvm -align-all-functions=2 under Arm Compiler -> Advanced Options -> Miscellaneous -> Miscellaneous C source specific flags and Miscellaneous C++ source specific flags:

Looking at the linked executable the size of the text has reduced.

Setting the above flags causes the -mllvm -align-all-functions=2 option to be passed to clang when only compiling C or C++ source files.

When initially tried adding  -mllvm -align-all-functions=2 under Miscellaneous flags the options were passed to clang also during linking, and it was during linking that the following was reported:

tiarmclang: warning: argument unused during compilation: '-mllvm -align-all-functions=2' [-Wunused-command-line-argument]

Hi Dhaval,

I selected the example in <SDK>/examples/industrial_comms/ethernetip_adapter_demo/mii/am243x-evm/r5fss0-0_freertos/ti-arm-clang.

I was able to reproduce your results using the release build configuration:

• No warning issued for make file build when adding the option to CFLAGS_common.
• Warning issued for CCS build adding option as you described. The warning is issued by the Linker.

For the CCS build, no warning is issued by the Linker when I add the option as described by Chester.

Dhaval Khandla said:

do see a difference of 0.2KB between memory consumption of binary generated by CCS and makefile.

For me, the difference is ~1.5 KB. Do you consider this a problem?

Regards,
Frank

Hi Dhaval,

I can't find any documentation for '-mllvm -align-all-functions=2'. Can you please point me to some documentation for this option?

Thanks and regards,
Frank

Hi
I could not find it in TI CLANG documentation.

There is a short explanation here : https://easyperf.net/blog/2018/01/25/Code_alignment_options_in_llvm#align-all-functions

Regards
Dhaval Khandla