Will all ARM compilers produce the same Assembly code and run on various CPUs?

Question

I have been developing code for an older device which has an NXP i.MX28 single core CPU which is ARM-based. The device runs Embedded Linux.

I am now upgrading to a better device which has an NXP i.MX6UL quad core processor, of course ARM-based also, and also running Embedded inux.

Is it normal that the same toolchain which I was using for the for building the code for the i.MX28 will also work for the i.MX6UL, even though the i.MX6UL is more advanced with more cores etc.?

I have built my code now for a test with the same compiler and even run it on a Rasberry Pi which seems to run ok. The Rasberry Pi uses a Broadcom BCM2711 SoC with an ARM Cortex-A72 processor which again is a different CPU.

I therefore must ask, will any ARM toolchain build code and be able to run on any type of ARM device regardless?

Answer 1

CPUs differ by the core architecture (incl. instruction set) and set of peripherals. Difference in the peripherals is solved by drivers and HALs. Difference in core arch is solved by the toolchain.

If the toolchain "knows" new arch it will emit the corresponding assembly code, that will run on the new CPU. So, compilers will not produdce the same assembly, but the same source code will run after rebuild, that's the idea of high-level languages.

Problems emerge when old code contains an inline assembly, or uses some specific DSP instructions or libraries