27 lines
775 B
ArmAsm
27 lines
775 B
ArmAsm
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.globl add64
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.text
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# > When primitive arguments twice the size of a pointer-word are passed on the
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# > stack, they are naturally aligned. When they are passed in the integer
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# > registers, they reside in an aligned even-odd register pair, with the even
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# > register holding the least-significant bits.
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# 64-bit integer addition
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# arguments:
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# a0: x lower 32 bits
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# a1: x upper 32 bits
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# a2: y lower 32 bits
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# a3: y upper 32 bits
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# return:
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# a0: x+y lower 32 bits
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# a1: x+y upper 32 bits
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#
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add64:
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add a0, a0, a2 # add lower 32 bits
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add t0, a1, a3 # add upper 32 bits
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sltu t1, a0, a2 # if lower 32-bit sum < a2 then set t1=1 (carry bit)
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add a1, t0, t1 # upper 32 bits of answer (upper sum + carry bit)
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ret
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