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Chapter 8 Integer Optimizations 183
Software Optimization Guide for AMD64 Processors
25112 Rev. 3.06 September 2005
or edx, '0' ; Convert 9th digit to ASCII.
mov [edi+8], dl ; Store 9th digit in memory.
lea edx, [esi+esi*4] ; 5 * fraction, new digit EDX[31-11]
shr ecx, 11 ; 5th digit
or ecx, '0' ; Convert 5th digit to ASCII.
mov [edi+4], cl ; Store 5th digit in memory.
shr edx, 11 ; 10th digit
or edx, '0' ; Convert 10th digit to ASCII.
mov [edi+9], dx ; Store 10th digit and end marker in memory.
pop ebx ; Restore register as per calling convention.
pop esi ; Restore register as per calling convention.
pop edi ; Restore register as per calling convention.
ret 8 ; Pop two DWORD arguments and return.
}
}
Binary-to-ASCII Decimal Conversion Suppressing Leading Zeros
__declspec(naked) void __stdcall uint_to_ascii_nlz(char *sptr, unsigned int x)
{
__asm {
push edi ; Save as per calling conventions.
push ebx ; Save as per calling conventions.
mov edi, [esp+12] ; sptr
mov eax, [esp+16] ; x
mov ecx, eax ; Save original argument.
mov edx, 89705F41h ; 1e-9 * 2^61 rounded
mul edx ; Divide by 1e9 by multiplying with reciprocal.
add eax, eax ; Round division result.
adc edx, 0 ; EDX[31-29] = argument / 1e9
shr edx, 29 ; Leading decimal digit, 0...4
mov eax, edx ; Leading digit
mov ebx, edx ; Initialize digit accumulator with
; leading digit.
imul eax, 1000000000 ; Leading digit * 1e9
sub ecx, eax ; Subtract (leading digit * 1e9) from argument.
or dl, '0' ; Convert leading digit to ASCII.
mov [edi], dl ; Store leading digit.
cmp ebx, 1 ; Any nonzero digit yet?
sbb edi, -1 ; Yes, increment ptr. No, keep old ptr.
mov eax, ecx ; Get reduced argument < 1e9.
mov edx, 0abcc7712h ; 2^28 / 1e8 * 2^30 rounded up
mul edx ; Divide reduced
shr eax, 30 ; argument < 1e9 by 1e8,
lea edx, [eax+4*edx+1] ; converting it into 4.28 fixed-point
mov eax, edx ; format such that 1.0 = 2^28.
shr eax, 28 ; Next digit
and edx, 0fffffffh ; Fraction part
or ebx, eax ; Accumulate next digit.
or eax, '0' ; Convert digit to ASCII.
mov [edi], al ; Store digit in memory.
lea eax, [edx*4+edx] ; 5 * fraction, new digit EAX[31-27]