forked from TCShenanigans/symphony_stdlib
92 lines
1.9 KiB
NASM
92 lines
1.9 KiB
NASM
; Multiplies r1 and r2, returning the lower part of the result
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; Arguments:
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; r1 - The first value
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; r2 - The second value
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; Result:
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; r1 - The lower 32 bits of the result
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; Clobbers: r2, r3, r4, r5
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pub mul_low:
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add r3, r2, r2 ; r3 = r2 * 2
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mov r4, 0 ; r4 has the result
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mul_low_loop:
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and r5, r1, 1 ; a0
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neg r5, r5 ; mask
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and r5, r2, r5 ; a0 ? r2 : 0
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add r4, r4, r5
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and r5, r1, 2 ; a1 is now 0 or 2
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lsr r5, r5, 1 ; normalize to 0/1
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neg r5, r5 ; mask
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and r5, r3, r5 ; a1 ? r2 * 2 : 0
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add r4, r4, r5
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lsl r2, r2, 2
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lsl r3, r3, 2
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lsr r1, r1, 2
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cmp r1, zr
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jne mul_low_loop
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mov r1, r4
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jmp r13
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; Calculates the absolute value of the value provided in the r1 register
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; Arguments:
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; r1 - The value for which we want the absolute value
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; Result:
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; r1 - The calculated absolute value
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; Clobbers: r2
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; Info: Based on Stanford's BitHacks
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pub abs: ; SHOULD BE INLINED
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; mask = v >> 31
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asr r2, r1, 31
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; v + mask
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add r1, r1, r2
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; return (v + mask) ^ mask
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xor r1, r1, r2
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jmp r13
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; Calculates the minimum value of the two values provided in the r1 and r2 registers
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; Arguments:
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; r1 - The first value
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; r2 - The second value
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; Result:
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; r1 - The smaller value
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; Clobbers: Nothing
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; Info: Based on Stanford's BitHacks
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pub min: ; SHOULD BE INLINED
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; x < y
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cmp r1, r2
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lsr flags, flags, 2
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; -(x < y)
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neg flags, flags
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; x ^ y
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xor r1, r1, r2
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; (x ^ y) & -(x < y)
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and r1, r1, flags
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; return y ^ ((x ^ y) & -(x < y))
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xor r1, r2, r1
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jmp r13
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; Calculates the maximum value of the two values provided in the r1 and r2 registers
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; Arguments:
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; r1 - The first value
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; r2 - The second value
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; Result:
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; r1 - The smaller value
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; Clobbers: r2
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; Info: Based on Stanford's BitHacks
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pub max: ; SHOULD BE INLINED
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; x < y
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cmp r1, r2
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lsr flags, flags, 2
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; -(x < y)
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neg flags, flags
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; x ^ y
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xor r2, r1, r2
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; (x ^ y) & -(x < y)
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and r2, r2, flags
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; return x ^ ((x ^ y) & -(x < y))
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xor r1, r1, r2
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jmp r13 |