49 lines
995 B
ArmAsm
49 lines
995 B
ArmAsm
/*
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* mpvecdigmul(mpdigit *b, int n, mpdigit m, mpdigit *p)
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*
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* p += b*m
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*
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* each step look like:
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* hi,lo = m*b[i]
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* lo += oldhi + carry
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* hi += carry
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* p[i] += lo
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* oldhi = hi
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*
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* the registers are:
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* hi = DX - constrained by hardware
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* lo = AX - constrained by hardware
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* b+n = SI - can't be BP
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* p+n = DI - can't be BP
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* i-n = BP
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* m = BX
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* oldhi = CX
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*
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*/
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TEXT mpvecdigmuladd(SB),$0
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MOVL b+0(FP),SI
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MOVL n+4(FP),CX
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MOVL m+8(FP),BX
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MOVL p+12(FP),DI
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MOVL CX,BP
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NEGL BP /* BP = -n */
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SHLL $2,CX
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ADDL CX,SI /* SI = b + n */
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ADDL CX,DI /* DI = p + n */
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XORL CX,CX
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_muladdloop:
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MOVL (SI)(BP*4),AX /* lo = b[i] */
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MULL BX /* hi, lo = b[i] * m */
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ADDL CX,AX /* lo += oldhi */
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ADCL $0, DX /* hi += carry */
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ADDL AX,(DI)(BP*4) /* p[i] += lo */
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ADCL $0, DX /* hi += carry */
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MOVL DX,CX /* oldhi = hi */
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INCL BP /* i++ */
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JNZ _muladdloop
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XORL AX,AX
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ADDL CX,(DI)(BP*4) /* p[n] + oldhi */
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ADCL AX,AX /* return carry out of p[n] */
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RET
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