Well, for a start you probably mean compiled for an arch with 16 registers. It doesn't actually matter what arch the compiler ran on (assuming modern cross-compiler like GCC).
If a program uses 16 registers then it needs 16 registers. But note it's the program itself that decides to use a frame pointer, it's not being reserved by the operating system or something. Programs don't even have to use the stack pointer as a stack pointer, they could use all 16 as general purpose, but in practice almost all programs use a call stack (I guess all C programs must do, but you might be able to disable it if you make no function calls?)
So the only change is that GCC and its toolkit will compile programs using a register as frame pointer by default? That seems like a very reasonable change. If having an extra general purpose register is critical for performance of then this can be disabled in that program's the makefile.
Correct and there are already known exceptions such as the python interpreter in which the “interpret function” function actually falls into this case and so for the foreseeable future python is going to continue to be compiled omitting frame pointers. But by default this destructive micro optimization is off by default until proven a performance bottleneck, just like any performance issue should be!
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Well, for a start you probably mean compiled for an arch with 16 registers. It doesn't actually matter what arch the compiler ran on (assuming modern cross-compiler like GCC).
If a program uses 16 registers then it needs 16 registers. But note it's the program itself that decides to use a frame pointer, it's not being reserved by the operating system or something. Programs don't even have to use the stack pointer as a stack pointer, they could use all 16 as general purpose, but in practice almost all programs use a call stack (I guess all C programs must do, but you might be able to disable it if you make no function calls?)
Ohh, I misunderstood what Ubuntu was doing.
So the only change is that GCC and its toolkit will compile programs using a register as frame pointer by default? That seems like a very reasonable change. If having an extra general purpose register is critical for performance of then this can be disabled in that program's the makefile.
Correct and there are already known exceptions such as the python interpreter in which the “interpret function” function actually falls into this case and so for the foreseeable future python is going to continue to be compiled omitting frame pointers. But by default this destructive micro optimization is off by default until proven a performance bottleneck, just like any performance issue should be!