I just got information that 'Harmony 3' example code for the Atmel Cortex-M processors will only support Microchip's XC32 compiler.
I am amazed that Microchip would take the time to try and make and sell an $1500 optimizing compiler, instead of taking the resources to fix all the errors in the datasheets. That is I do not need more optimization from GCC I need better documentation to write good stable peripheral drivers. For example the datasheets for the SAMD series chips indicate the pull ups and pull downs work with peripherals (SERCOM) where they do not. The SAMD51 datasheet for the I2S is so bad it is more trial and error to try and get it to work.
I do not know an single engineer that has a said the optimization on GCC is bad and we need a better compiler, I do know several engineers who have complained about the poorly written datasheets.