AMD 250 manual Binary-to-ASCII Decimal Conversion Suppressing Leading Zeros, 183

25112 Rev. 3.06 September 2005 Software Optimization Guide for AMD64 Processors

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]

Chapter 8 Integer Optimizations 183