76 lines
2.1 KiB
ArmAsm
76 lines
2.1 KiB
ArmAsm
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@---------------------------------------------------------------------------------
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@ Setup some nicer names
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@---------------------------------------------------------------------------------
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numerator .req r0
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denominator .req r1
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accumulator .req r2
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current_bit .req r3
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numerator_signed .req r12
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denominator_signed .req r3
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sign_flip .req r12
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result .req r0
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remainder .req r1
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result_abs .req r3
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temp .req r3
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@---------------------------------------------------------------------------------
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.global swi_DivARM
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.type swi_DivARM STT_FUNC
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swi_DivARM:
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@---------------------------------------------------------------------------------
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mov temp, numerator
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mov numerator, denominator
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mov denominator, temp
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b swi_Div
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@---------------------------------------------------------------------------------
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.global swi_Div
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.type swi_Div STT_FUNC
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swi_Div:
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@ See http://www.tofla.iconbar.com/tofla/arm/arm02/index.htm for more information
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@---------------------------------------------------------------------------------
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@ Set if numerator is signed, and abs numerator
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ands numerator_signed, numerator, #0x80000000
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rsbmi numerator, numerator, #0
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// Same with denominator
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ands denominator_signed, denominator, #0x80000000
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rsbmi denominator, denominator, #0
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// Gets set if sign(numerator) != sign(denominator)
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eor sign_flip, numerator_signed, denominator_signed
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mov accumulator, #0
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mov current_bit, #1
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// This moves out the current bit to the MSB of the denominator,
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// and aligns the denominator up to the same bit-length as the
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// numerator
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0:
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cmp denominator, numerator
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movls denominator, denominator, lsl #1
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movls current_bit, current_bit, lsl #1
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bls 0b
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// Basically the grade-school algorithm, for unsigned integers in binary
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1:
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cmp numerator, denominator
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subcs numerator, numerator, denominator
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orrcs accumulator, accumulator, current_bit
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movs current_bit, current_bit, lsr #1
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movcc denominator, denominator, lsr #1
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bcc 1b
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mov remainder, numerator
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mov result_abs, accumulator
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mov result, accumulator
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tst sign_flip, #0x80000000
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rsbmi result, result, #0
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bx lr
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