33 lines
1.2 KiB
Markdown
33 lines
1.2 KiB
Markdown
# Calling Convention — Output Explanation
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This document explains the output of the calling convention algorithm
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implemented in `calling-convention.ipynb`, tested across 3 scenarios.
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---
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## TEST 1: A single 1-byte argument
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**Function signature:** `result = func(x)` where `x` is 8 bits (1 byte)
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**Output:**
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```
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===== TEST 1: a 1 byte argument =====
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=== State after do_function_call ===
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Registers used: ['RA']
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Stack: [{'type': 'caller_saved', 'reg': 'R0', 'value': 0}, {'type': 'caller_saved', 'reg': 'R1', 'value': 0}, {'type': 'caller_saved', 'reg': 'R2', 'value': 0}, {'type': 'caller_saved', 'reg': 'R3', 'value': 0}]
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RS points to: 4
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=== State after undo_function_call ===
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Clean stack: []
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RS: 0
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Collected result: {'result': {'type': 'result', 'value': 42}}
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```
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**Explanation:**
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Since there is only one argument and it fits in a single register, it is
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placed directly in `RA` (the first available argument register).
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Before the call, the 4 caller-saved registers (R0-R3) are pushed onto the
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stack to preserve their values. `RS` points to position 4, reflecting those
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4 entries. After `undo_function_call`, the stack is empty, `RS` returns to 0,
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and the result value `42` is successfully collected from `RA`.
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