Key difference between ARM compiler 5 and compiler 6

ARM Compiler 5 (and earlier versions) use the armcc compiler.  ARM Compiler 6 replaces armcc with armclang, so a new compiler.

armclang is based on LLVM. It has different command line arguments, directives, etc... Which means a degree of porting is needed to move between compilers. There is some guidance in the docs to help with this.

In terms of choosing between them the choice is currently reasonably straight forward. ARM Compiler 6 supports ARMv8-A, ARM Compiler 5 only supports up to ARMv7.

ARM Compiler 5 (and earlier versions) use the armcc compiler.  ARM Compiler 6 replaces armcc with armclang, so a new compiler.

armclang is based on LLVM. It has different command line arguments, directives, etc... Which means a degree of porting is needed to move between compilers. There is some guidance in the docs to help with this.

In terms of choosing between them the choice is currently reasonably straight forward. ARM Compiler 6 supports ARMv8-A, ARM Compiler 5 only supports up to ARMv7.

ARM Compiler 6 supports GNU assembly codes.

It still ships with armasm as well, so assembler files written for ARM Compiler 5 (or earlier) can be used.

Thank you!

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0742a/index.html explains the differences in more detail, if you need more details.