Some context: my target has 2 general purpose registers and 1 stack
pointer: %a, %b, %sp.
%sp can only be written to from %a, and cannot be read;
However it can be used as an address operand with an offset, as follows:
move *( %sp + offset), %r
file test.c:
int main() {
int a = 2;
}
fails to compile with the following message:
test.c: In function 'main':
test.c:4:1: error: unable to find a register to spill
}
^
test.c:4:1: error: this is the insn:
(insn 5 16 17 2 (set (reg:HI 12)
(const_int 2 [0x2])) test.c:3 1 {movhi}
(nil))
test.c:4: confused by earlier errors, bailing out
(reg:HI 12) must be referring to a pseudo, as I only have 4 registers total.
Does this mean that I simply do not have any free registers to start
pushing values onto the stack?
Potentially relevant excerpt from my macro definitions, currently
arbitrarily defined:
// Frame Registers
#define STACK_POINTER_REGNUM 2 // Stack pointer register
#define FRAME_POINTER_REGNUM 0 // register A
#define ARG_POINTER_REGNUM 0
#define STATIC_CHAIN_REGNUM 1 // register B
