Compiler/TM4C129XNCZAD: TI ARM v20.2.3.LTS compiler doesn't seem to support code alignment

Tool/software: TI C/C++ Compiler

The ARM Optimizing C/C++ Compiler v20.2.0.LTS User's Guide says that either of the following can be used to control the alignment of the starting address for a function:

• The CODE_ALIGN Pragma
• The GCC-style aligned function attribute

However, with the TI ARM v20.2.3.LTS compiler neither of those mechanisms seem to work:

1. Trying to use the CODE_ALIGN Pragma results in warning #163-D: unrecognized #pragma
2. Trying to use the GCC-style aligned function attribute doesn't report a warning, but the linker map shows the function starting address has not been given the requested alignment. The generated assembler, saved with --keep_asm, doesn't show any .align assembler directive used for the function.

The attached project demonstrates this, in that attempted to set 32-byte alignment on the test and main function using the two mechanisms. The addresses from the linker map show the requested alignment has not been set:

000002a9  main                          
0000029f  test                          

code_align_ARM.zip

I found the CODE_ALIGN and aligned function attribute do work with the C2000 v20.2.3.LTS compiler; in the generate assembler you can see the compiler emits .align assembler directives.

Is it a bug in the TI ARM compiler that the CODE_ALIGN and aligned function attribute don't work, or should they be removed from the user's guide?

A work-around for functions which require alignment on their starting address is to place them in their own section and specify the alignment for the section in the linker command file.