48 lines
1.1 KiB
NASM
48 lines
1.1 KiB
NASM
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; ************************
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; ** Start Data Block **
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; ************************
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SECTION .data
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extern fpuasm
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extern reciptable
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global _asm_krecipasm
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; ************************
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; ** Start Code Block **
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; ************************
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SEGMENT .text
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; Ignore all the 'offset's in the code AH
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%idefine offset
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ALIGN 16
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; "mov fpuasm, eax",\
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; "fild dword ptr fpuasm",\
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; "add eax, eax",\
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; "fstp dword ptr fpuasm",\
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; "sbb ebx, ebx",\
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; "mov eax, fpuasm",\
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; "mov ecx, eax",\
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; "and eax, 0x007ff000",\
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; "shr eax, 10",\
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; "sub ecx, 0x3f800000",\
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; "shr ecx, 23",\
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; "mov eax, dword ptr reciptable[eax]",\
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; "sar eax, cl",\
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; "xor eax, ebx",\
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_asm_krecipasm:
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mov [fpuasm], eax ; Store parameter to memory
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fild dword [fpuasm] ; Convert the 32-bit int to a fp
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add eax, eax ; Double the int param's value
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fstp dword [fpuasm] ; Put the 32-bit float to memory
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sbb ebx, ebx ; Puts 0 - (carry bit) into ebx AFFECTED BY "add eax eax"!!!
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mov eax, dword [fpuasm]
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mov ecx, eax
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and eax, 007ff000h
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shr eax, 10
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sub ecx, 03f800000h
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shr ecx, 23
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mov eax, dword [reciptable + eax]
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sar eax, cl
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xor eax, ebx
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ret
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