| Register Usage |
| rax temporary register; with variable arguments passes information |
| about the number of SSE registers used; 1st return register |
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| rbx* callee-saved register; optionally used as base pointer |
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| rcx used to pass 4th integer argument to functions |
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| rdx used to pass 3rd argument to functions 2nd return register |
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| rsp* stack pointer |
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| rbp* callee-saved register; optionally used as frame pointer |
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| rsi used to pass 2nd argument to functions |
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| rdi used to pass 1st argument to functions |
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| r8 used to pass 5th argument to functions |
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| r9 used to pass 6th argument to functions |
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| r10 temporary register, used for passing a function's static chain pointer |
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| r11 temporary register |
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| r12-15* callee-saved registers |
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| xmm01 used to pass and return floating point arguments |
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| xmm27 used to pass floating point arguments |
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| xmm815 temporary registers |
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| mmx07 temporary registers |
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| st0 temporary register; used to return long double arguments |
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| st1 temporary registers; used to return long double arguments |
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| st27 temporary registers |
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| fs Reserved for system use (as thread specific data register) |
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| *) must be preserved across function calls |
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| Integer arguments from list: rdi,rsi,rdx,rcx,r8,r9,stack |
| Floating point arguments from list: xmm0-xmm7 |
