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subttl emfmul.asm - Multiplication page;*******************************************************************************; Copyright (c) Microsoft Corporation 1991; All Rights Reserved;;emfmul.asm - long double multiply; by Tim Paterson;;Purpose:; Long double multiplication.;Inputs:; ebx:esi = op1 mantissa; ecx = op1 sign in bit 15, exponent in high half; edi = pointer to op2 and result location; [Result] = edi;; Exponents are unbiased. Denormals have been normalized using; this expanded exponent range. Neither operand is allowed to be zero.;Outputs:; Jumps to [RoundMode] to round and store result.;;Revision History:;; [] 09/05/91 TP Initial 32-bit version.;;*******************************************************************************
;Dispatch table for multiply;;One operand has been loaded into ecx:ebx:esi ("source"), the other is;pointed to by edi ("dest"). ;;Tag of source is shifted. Tag values are as follows:
.erre TAG_SNGL eq 0 ;SINGLE: low 32 bits are zero.erre TAG_VALID eq 1.erre TAG_ZERO eq 2.erre TAG_SPCL eq 3 ;NAN, Infinity, Denormal, Empty
;Any special case routines not found in this file are in emarith.asm
tFmulDisp label dword ;Source (reg) Dest (*[di]) dd MulSingle ;single single dd MulDouble ;single double dd XorDestSign ;single zero dd MulSpclDest ;single special dd MulDouble ;double single dd MulDouble ;double double dd XorDestSign ;double zero dd MulSpclDest ;double special dd XorSourceSign ;zero single dd XorSourceSign ;zero double dd XorDestSign ;zero zero dd MulSpclDest ;zero special dd MulSpclSource ;special single dd MulSpclSource ;special double dd MulSpclSource ;special zero dd TwoOpBothSpcl ;special special dd XorDestSign ;Two infinities
EM_ENTRY eFIMUL16eFIMUL16: push offset MulSetResult jmp Load16Int ;Returns to MulSetResult
EM_ENTRY eFIMUL32eFIMUL32: push offset MulSetResult jmp Load32Int ;Returns to MulSetResult
EM_ENTRY eFMUL32eFMUL32: push offset MulSetResult jmp Load32Real ;Returns to MulSetResult
EM_ENTRY eFMUL64eFMUL64: push offset MulSetResult jmp Load64Real ;Returns to MulSetResult
EM_ENTRY eFMULPregeFMULPreg: push offset PopWhenDone
EM_ENTRY eFMULregeFMULreg: xchg esi,edi
EM_ENTRY eFMULtopeFMULtop: mov ecx,EMSEG:[esi].ExpSgn mov ebx,EMSEG:[esi].lManHi mov esi,EMSEG:[esi].lManLoMulSetResult: mov ebp,offset tFmulDisp mov EMSEG:[Result],edi ;Save result pointer mov al,cl or al,EMSEG:[edi].bTag cmp al,bTAG_VALID.erre bTAG_VALID eq 1.erre bTAG_SNGL eq 0 jz MulDouble ja TwoOpResultSet;.erre MulSingle eq $ ;Fall into MulSingle
;*********MulSingle:;*********
mov edx,EMSEG:[edi].ExpSgn mov eax,EMSEG:[edi].lManHi
;op1 mantissa in ebx:esi, exponent in high ecx, sign in ch bit 7;op2 high mantissa in eax, exponent in high edx, sign in dh bit 7
xor ch,dh ;Compute result sign xor dx,dx ;Clear out sign and tag add ecx,edx ;Result exponent.erre TexpBias eq 0 ;Exponents not biased jo SMulBigUnderflow ;Multiplying two denormalsContSmul:
;Value in ecx is correct exponent if result is not normalized.;If result comes out normalized, 1 will be added.
mul ebx ;Compute product mov ebx,edx mov esi,eax xor eax,eax ;Extend with zero
;Result in ebx:esi:eax;ecx = exponent minus one in high half, sign in ch or ebx,ebx ;Check for normalization jns ShiftOneBit ;In emfadd.asm add ecx,1 shl 16 ;Adjust exponent jmp EMSEG:[RoundMode]
SMulBigUnderflow: or EMSEG:[CURerr],Underflow add ecx,Underbias shl 16 ;Fix up exponent test EMSEG:[CWmask],Underflow ;Is exception masked? jz ContSmul ;No, continue with multiplyUnderflowZero: or EMSEG:[CURerr],PrecisionSignedZero: and ecx,bSign shl 8 ;Preserve sign bit xor ebx,ebx mov esi,ebx mov cl,bTAG_ZERO jmp EMSEG:[ZeroVector]
;*******************************************************************************
DMulBigUnderflow:;Overflow flag set could only occur with denormals (true exp < -32768) or EMSEG:[CURerr],Underflow test EMSEG:[CWmask],Underflow ;Is exception masked? jnz UnderflowZero ;Yes, return zero add ecx,Underbias shl 16 ;Fix up exponent jmp ContDmul ;Continue with multiply
PolyMulToZero: ret ;Return the zero in registers
PolyMulDouble:;This entry point is used by polynomial evaluator.;It checks the operand in registers for zero. cmp cl,bTAG_ZERO ;Adding to zero? jz PolyMulToZero
;*********MulDouble:;*********
mov eax,EMSEG:[edi].ExpSgn mov edx,EMSEG:[edi].lManHi mov edi,EMSEG:[edi].lManLo
MulDoubleReg: ;Entry point used by transcendentals;op1 mantissa in ebx:esi, exponent in high ecx, sign in ch bit 7;op2 mantissa in edx:edi, exponent in high eax, sign in ah bit 7
xor ch,ah ;Compute result sign xor ax,ax ;Clear out sign and tag add ecx,eax ;Result exponent.erre TexpBias eq 0 ;Exponents not biased jo DMulBigUnderflow ;Multiplying two denormalsContDmul:
;Value in ecx is correct exponent if result is not normalized.;If result comes out normalized, 1 will be added.
mov ebp,edx ;edx is used by MUL instruction
;Generate and sum partial products, from least to most significant
mov eax,edi mul esi ;Lowest partial product add eax,-1 ;CY set IFF eax<>0 sbb cl,cl ;Sticky bit: 0 if zero, -1 if nz xchg edi,edx ;Save high result
;First product: cl reflects low dword non-zero (sticky bit), edi has high dword
mov eax,ebx mul edx add edi,eax adc edx,0 ;Sum first results xchg edx,esi ;High result to esi
;Second product: accumulated in esi:edi:cl
mov eax,ebp ;Next mult. to eax mul edx add edi,eax ;Sum low results adc esi,edx ;Sum high results mov eax,ebx mov ebx,0 ;Preserve CY flag adc ebx,ebx ;Keep carry out of high sum
;Third product: accumulated in ebx:esi:edi:cl
mul ebp add esi,eax adc ebx,edx mov eax,edi or al,cl ;Collapse sticky bits into eax
;Result in ebx:esi:eax;ecx = exponent minus one in high half, sign in chMulDivNorm: or ebx,ebx ;Check for normalization jns ShiftOneBit ;In emfadd.asm add ecx,1 shl 16 ;Adjust exponent jmp EMSEG:[RoundMode]
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