69 lines
1.4 KiB
ArmAsm
69 lines
1.4 KiB
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# * BASIC_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Math package - denormalize FAC1 mantissa and adapt its exponent accordingly for division
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//
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div_FAC1_denorm:
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// Set FACOV to 0, no need for increased precision here
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lda #$00
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sta FACOV
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// Start by moving whole bytes, if possible
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lda FAC1_mantissa+3
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bne div_FAC1_denorm_by_bit // branch if last byte of mantissa is non-zero
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lda FAC1_exponent
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cmp #$08
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bcc div_FAC1_denorm_by_bit // branch if not suitable to increment exponent by 8
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// Increment exponent
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sbc #$08 // Carry already sec
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sta FAC1_exponent
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// Move mantissa bytes
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lda FAC1_mantissa+2
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sta FAC1_mantissa+3
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lda FAC1_mantissa+1
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sta FAC1_mantissa+2
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lda FAC1_mantissa+0
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sta FAC1_mantissa+1
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lda #$00
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sta FAC1_mantissa+0
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beq div_FAC1_denorm // branch always
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div_FAC1_denorm_by_bit:
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lda FAC1_mantissa+3
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and #$01
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bne div_FAC1_denorm_done // branch if lowest bit of mantissa is already 1
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lda FAC1_exponent
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beq div_FAC1_denorm_done // branch if not suitable to decrement exponent
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// Decrement exponent
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dec FAC1_exponent
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// Move mantissa bits
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clc
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ror FAC1_mantissa+0
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ror FAC1_mantissa+1
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ror FAC1_mantissa+2
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ror FAC1_mantissa+3
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bcc div_FAC1_denorm_by_bit // branch always
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div_FAC1_denorm_done:
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rts
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