feat(L08): add subroutines and ABI card

tests/reference_model.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+import sys
+
+
+def task01():
+    pc = 0x100
+    assert pc + 24 == 0x118 and pc + 4 == 0x104
+    assert ((0x205 - 4) & ~1) == 0x200
+    print("PASS task01 jal_target=00000118 link=00000104 jalr_target=00000200")
+
+
+def abi_class(index):
+    if index == 0: return "zero"
+    if index == 1: return "ra"
+    if index == 2: return "sp"
+    if 10 <= index <= 17: return "arg"
+    if index in (8, 9) or 18 <= index <= 27: return "saved"
+    if 5 <= index <= 7 or 28 <= index <= 31: return "temp"
+    return "system"
+
+
+def task02():
+    classes = [abi_class(index) for index in range(32)]
+    assert classes.count("arg") == 8 and classes.count("saved") == 12
+    assert classes.count("temp") == 7 and sum(classes.count(x) for x in ("zero", "ra", "sp", "system")) == 5
+    print("PASS task02 args=8 saved=12 temporaries=7 fixed=5")
+
+
+def task03():
+    stack = []
+    stack.extend([0x104, 0x204])
+    returns = [stack.pop(), stack.pop()]
+    underflow = not stack
+    assert returns == [0x204, 0x104] and underflow
+    print("PASS task03 returns=00000204,00000104 underflow=1 max_depth=2")
+
+
+TASKS = {"task01_link_address": task01, "task02_abi_registers": task02, "task03_call_stack": task03}
+if len(sys.argv) != 2 or sys.argv[1] not in TASKS:
+    raise SystemExit(f"usage: {sys.argv[0]} {'|'.join(TASKS)}")
+TASKS[sys.argv[1]]()