1. Runtime Stack Activation record for hanoi; 1 2 3 1
Activation record for main

2. Support for Function Calls
Call usually simple, but setup not
call printf
what comes before and after call?
Support recursion?
No --- simple, use static space
Yes --- runtime stack of activation record(s)
Return value(s)

3. Activation Record Information
Parameters
Locals
Compiler Temporaries
Register Save/Restore
Previous Activation Record
Previous Scope
Anything else?

4. A Function Call Convention
fp and sp defined by assembler
Caller function (in order)
push parameters on stack, in reverse
push fp
fp = sp - 4
call callee
fp = 0 (fp)
sp = sp – (size of arguments + 4)
Callee function (in order)
sp = sp + size of function
execute function
sp = sp – size of function
return

5. An Activation Record sp fp Next stack location – beyond the stack
Reg save …
Reg save …
Reg save …
Temps …
8(fp) – local 2
4(fp) – local 1 fp
0(fp) – old fp
-4(fp) – parameter 1
-8(fp) – parameter 2
-12(fp) – parameter 3

6. Function Call Convention (2)
Alpha conventions
Parameters passed in registers, r16 - r24 or d16 - d24
Return in r0 (or d0)
Registers r1 - r8, d1 - d8 are NOT saved across function call invocations (caller save)
Registers r25 - r31 and d25 - d31 ARE saved across function call invocations (callee save)