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CMP instructions prolly important smh

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cannoli-fruit 2026-07-24 16:17:25 -04:00
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ISA.md
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@ -245,6 +245,14 @@ Opcode Table
+-----------+----------+---------------------------------------------------------------------------+
| Xor64 | 01111011 | Xor64 dst, src performs logical xor dst with src |
+-----------+----------+---------------------------------------------------------------------------+
| Cmp64 | 01111101 | See Cmp section |
+-----------+----------+---------------------------------------------------------------------------+
| Cmp32 | 01111100 | See Cmp Section |
+-----------+----------+---------------------------------------------------------------------------+
| ICmp64 | 01111111 | See Cmp section |
+-----------+----------+---------------------------------------------------------------------------+
| ICmp32 | 01111110 | See Cmp Section |
+-----------+----------+---------------------------------------------------------------------------+
| FAdd | 10000000 | FAdd dst, src adds src to dst as 32 bit float |
+-----------+----------+---------------------------------------------------------------------------+
| FSub | 10000001 | FSub dst, src subtracts src from dst as 32 bit float |
@ -330,6 +338,17 @@ Opcode Table
| Ret | 00000010 | Returns from current function to parent function |
+-----------+----------+---------------------------------------------------------------------------+
Comparisons:
Cmp32, Cmp64, ICmp32 & ICmp64 directly set flags based on a pair of values A and B
Based on the result of A-B assuming a sign extension (no dealing with wrapping)
And therefore should be used for i.e r8 > r9 as in:
ICmp64 r8, r9
JmpIP greater
less_or_eq:
; ...
greater:
; ...
Calling algorithm:
This is some horrific mix of c and asm but yk
void call(uint64_t addr) {