[x86_64] Status flags undefined for mul/div/idiv
The following table summerizes how Mu integer binops are mapped to x86_64 insts, and how x86_64 insts affect status flags.
| Mu IR | X86_64 Inst | #N (signed) | #Z (zero) | #C (carry) | #V (overflow) |
|---|---|---|---|---|---|
| ADD | add | ✓ | ✓ | ✓ | ✓ |
| SUB | sub | ✓ | ✓ | ✓ | ✓ |
| AND | and | ✓ | ✓ | - | - |
| OR | or | ✓ | ✓ | - | - |
| XOR | xor | ✓ | ✓ | - | - |
| MUL | mul | ✗ | ✗ | ✓ | ✓ |
| UDIV | div | ✗ | ✗ | - | - |
| SDIV | idiv | ✗ | ✗ | - | - |
| UREM | div | ✗ | ✗ | - | - |
| SREM | idiv | ✗ | ✗ | - | - |
| SHL | shl | ✓ | ✓ | - | - |
| LSHR | shr | ✓ | ✓ | - | - |
| ASHR | sar | ✓ | ✓ | - | - |
mul, div and idiv generate undefined signed flag (#N), and zero flag(#Z). We will need to generate extra code to check, and set those flags.