35 lines
903 B
ArmAsm
35 lines
903 B
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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; This file is under the MIT license, it contains code released by Microsoft Corporation.
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; See LICENSE for more information.
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; Math package - shift carry into FAC1
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;
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; This is verified to be identical to the original Microsoft implementation where it was named SQUEEZ.
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;
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; Alternative entry point: RNDSHF to also shift in a CF=0
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;
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; See also:
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; - [CM64] Computes Mapping the Commodore 64 - page 113
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; - https://www.c64-wiki.com/wiki/Floating_point_arithmetic
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; - https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics
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;
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shift_carry_into_FAC1:
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SQUEEZ:
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bcc RNDRTS
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RNDSHF:
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inc FAC1_exponent
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beq overflow_error
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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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ror FACOV
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RNDRTS:
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rts
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