Even if compilers are better now, if possible it is better to wrap any IO memory access into ioread/iowrite inline (no cost) functions.
This can then be implemented in a way known to be safe for the compiler used. And that can be changed easily in case the architecture or the compiler changes ( yeah abstraction ! )
I have, in various projects over the years, resorted to inline Asm when I couldn't coerce the compiler to do exactly what I wanted; including very rare compiler bugs.
We found bugs in that one as well. ARM even sent us their pre-release binaries some time. We had pretty templaze-heavy code and unit tests. When Visual Studio and gcc (and the standard) agreed on one outcome and RealView on another, we reported it. Record was three hours after receiving the compiler we reported a bug.
One ARM person once said: "You know, we thought we build these CPUs, so we'd be the ones optimizing best for it. Boy did we learn how complicated C++ is. Next version will be based on clang..."
Somewhere there's this great CMSIS-DSP ticket: creator complains that CMSIS uses volatile loads/stores for GCC. Creator remove volatile, GCC reorders instructions to require larger number of in-flight registers, spills everything to the stack and tanks the FFT speed.
Even if compilers are better now, if possible it is better to wrap any IO memory access into ioread/iowrite inline (no cost) functions. This can then be implemented in a way known to be safe for the compiler used. And that can be changed easily in case the architecture or the compiler changes ( yeah abstraction ! )
As linux does for example: https://www.kernel.org/doc/html/v4.15/driver-api/device-io.h...
Ouch (assuming that this required them to pay to get the bugfix.)
The 4.x compiler line never being patched was a bit of eye opener into commercial toolchain support.
Wow does it ever suck and waste a ton of time when it IS the compiler. I feel sorrow for whomever had to find this out in their workflow
One ARM person once said: "You know, we thought we build these CPUs, so we'd be the ones optimizing best for it. Boy did we learn how complicated C++ is. Next version will be based on clang..."