diff options
| -rw-r--r-- | Variables.py | 3 | ||||
| -rw-r--r-- | notes.txt | 5 | ||||
| -rw-r--r-- | tests/params.c | 4 |
3 files changed, 8 insertions, 4 deletions
diff --git a/Variables.py b/Variables.py index 89c8501..26de704 100644 --- a/Variables.py +++ b/Variables.py @@ -48,7 +48,8 @@ class Variables(object): # XXX don't hardcode R5 return ("R5", str(-self.local_vars[name])) try: - return ("R5", str(1 + self.param_vars.index(name))) + # 1 for the return address, 1 for the stored BP + return ("R5", str(2 + self.param_vars.index(name))) except ValueError: pass # lookup in the parent @@ -26,7 +26,8 @@ Caller: Callee: 1. push R5 (base pointer "BP" in stack for local variables and parameters) 2. Store current stack pointer in R5 (LOAD R5 SP). [R5] now contains the return - address, [R5+i] the i-th parameter and [R5+-i] the i-th local var + address, [R5+i+1] the i-th parameter and [R5+-i] the i-th local var. Param i + is at R5 + i + 1 because BP was pushed too 3. Grow stack for local variables (by SUB SP n) if necessary 4. <function body> 5. LOAD SP R5 (clear local vars) @@ -34,7 +35,7 @@ Callee: 6. RTS (go back to caller) parameter access (i-th parameter): -LOAD R0 [R5+i] +LOAD R0 [R5+i+1] local variable access (i-th local var) LOAD R0 [R5+-i] global variable access diff --git a/tests/params.c b/tests/params.c index eb91b83..2232fdd 100644 --- a/tests/params.c +++ b/tests/params.c @@ -1,5 +1,7 @@ int square(int x) { - return x * x; + int res; + res = x * x; + return res; } int main() { int x; |