21.6.5 Registers That Form a Stack

There are special features to handle computers where some of the "registers" form a stack, as in the 80387 coprocessor for the 80386. Stack registers are normally written by pushing onto the stack, and are numbered relative to the top of the stack.

Currently, GCC can only handle one group of stack-like registers, and they must be consecutively numbered.

STACK_REGS

Define this if the machine has any stack-like registers.

FIRST_STACK_REG

The number of the first stack-like register. This one is the top of the stack.

LAST_STACK_REG

The number of the last stack-like register. This one is the bottom of the stack.