108 lines
2.2 KiB
ArmAsm
108 lines
2.2 KiB
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
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// #LAYOUT# * BASIC_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Math package - add FAC2 to FAC1, subtraction part
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//
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// XXX test this
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add_FAC2_FAC1_sub:
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// First verify that |FAC1| > |FAC2|, branch to proper variant if it is not
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// Note, that exponents are laready equalized
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lda FAC1_mantissa+0
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cmp FAC2_mantissa+0
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bcc add_FAC2_FAC1_sub_rev // if FAC1 < FAC2, branch
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bne !+ // if FAC1 > FAC2, branch
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lda FAC1_mantissa+1
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cmp FAC2_mantissa+1
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bcc add_FAC2_FAC1_sub_rev // if FAC1 < FAC2, branch
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bne !+ // if FAC1 > FAC2, branch
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lda FAC1_mantissa+2
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cmp FAC2_mantissa+2
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bcc add_FAC2_FAC1_sub_rev // if FAC1 < FAC2, branch
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bne !+ // if FAC1 > FAC2, branch
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lda FAC1_mantissa+3
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cmp FAC2_mantissa+3
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bcc add_FAC2_FAC1_sub_rev // if FAC1 < FAC2, branch
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bne !+ // if FAC1 > FAC2, branch
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// If we are here, than FAC1 is equal to FAC2 - so just set FAC1 to 0
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lda #$00
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sta FAC1_exponent
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rts
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!:
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// Perform the subtration, FAC1 = FAC1 - FAC2
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sec
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lda FAC1_mantissa+3
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sbc FAC2_mantissa+3
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sta FAC1_mantissa+3
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lda FAC1_mantissa+2
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sbc FAC2_mantissa+2
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sta FAC1_mantissa+2
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lda FAC1_mantissa+1
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sbc FAC2_mantissa+1
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sta FAC1_mantissa+1
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lda FAC1_mantissa+0
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sbc FAC2_mantissa+0
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sta FAC1_mantissa+0
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bcs add_FAC2_FAC1_sub_normalize // end if no need to adapt the exponent
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dec FAC1_exponent
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jmp normal_FAC1
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add_FAC2_FAC1_sub_rev:
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// Since |FAC1| < |FAC2|, toggle FAC1 sign before subtraction
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jsr toggle_sign_FAC1_skipcheck
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// Perform the subtration, FAC1 = FAC2 - FAC1
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sec
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lda #$00
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sbc FACOV
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sta FACOV
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lda FAC2_mantissa+3
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sbc FAC1_mantissa+3
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sta FAC1_mantissa+3
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lda FAC2_mantissa+2
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sbc FAC1_mantissa+2
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sta FAC1_mantissa+2
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lda FAC2_mantissa+1
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sbc FAC1_mantissa+1
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sta FAC1_mantissa+1
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lda FAC2_mantissa+0
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sbc FAC1_mantissa+0
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sta FAC1_mantissa+0
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bcs add_FAC2_FAC1_sub_normalize // end if no need to adapt the exponent
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lda FAC2_exponent
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sta FAC1_exponent
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dec FAC1_exponent
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// FALLTROUGH
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add_FAC2_FAC1_sub_normalize:
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jmp normal_FAC1
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