[adrian_b]

32 registers have been used in many CPUs since the mid seventies until today, i.e. for a half of century.

During all this time there has been a consensus that 32 registers are better than less registers.

A few CPUs, e.g. SPARC and Itanium have tried to use more registers than that, and they have been considered unsuccessful.

There have been some inconclusive debates about whether 64 architectural registers might be better than 32 registers, but the fact the 32 are better than 16 has been pretty much undisputed. So there are chances that 32 is close to an optimal number of GPRs.

Using 32 registers is something new only for Intel-AMD, due to their legacy, but it is something that all their competition has used successfully for many decades.

I have written many assembly language programs for ARM, POWER or x86. Whenever I had 32 registers, this made it much easier for me to avoid most memory accesses, for spilling or for other purposes. It is true that a compiler is dumber than a human programmer and it frequently has to adhere to a rigid ABI, but even so, I expect that on average even a compiler will succeed to reduce the register spilling when using 32 registers.