136 lines
2.3 KiB
ArmAsm
136 lines
2.3 KiB
ArmAsm
#include <sys/asm.h>
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#if BYTE_ORDER != LITTLE_ENDIAN
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# error
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#endif
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.text
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.globl strcmp
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strcmp:
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or a4, a0, a1
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li t2, -1
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and a4, a4, SZREG-1
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bnez a4, .Lmisaligned
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#if SZREG == 4
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li t3, 0x7f7f7f7f
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#else
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ld t3, mask
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#endif
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.macro check_one_word i n
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REG_L a2, \i*SZREG(a0)
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REG_L a3, \i*SZREG(a1)
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and t0, a2, t3
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or t1, a2, t3
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add t0, t0, t3
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or t0, t0, t1
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bne t0, t2, .Lnull\i
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.if \i+1-\n
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bne a2, a3, .Lmismatch
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.else
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add a0, a0, \n*SZREG
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add a1, a1, \n*SZREG
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beq a2, a3, .Lloop
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# fall through to .Lmismatch
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.endif
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.endm
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.macro foundnull i n
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.ifne \i
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.Lnull\i:
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add a0, a0, \i*SZREG
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add a1, a1, \i*SZREG
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.ifeq \i-1
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.Lnull0:
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.endif
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bne a2, a3, .Lmisaligned
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li a0, 0
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ret
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.endif
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.endm
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.Lloop:
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# examine full words at a time, favoring strings of a couple dozen chars
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#if __riscv_xlen == 32
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check_one_word 0 5
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check_one_word 1 5
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check_one_word 2 5
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check_one_word 3 5
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check_one_word 4 5
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#else
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check_one_word 0 3
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check_one_word 1 3
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check_one_word 2 3
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#endif
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# backwards branch to .Lloop contained above
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.Lmismatch:
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# words don't match, but a2 has no null byte.
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#if __riscv_xlen == 64
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sll a4, a2, 48
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sll a5, a3, 48
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bne a4, a5, .Lmismatch_upper
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sll a4, a2, 32
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sll a5, a3, 32
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bne a4, a5, .Lmismatch_upper
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#endif
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sll a4, a2, 16
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sll a5, a3, 16
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bne a4, a5, .Lmismatch_upper
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srl a4, a2, 8*SZREG-16
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srl a5, a3, 8*SZREG-16
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sub a0, a4, a5
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and a1, a0, 0xff
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bnez a1, 1f
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ret
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.Lmismatch_upper:
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srl a4, a4, 8*SZREG-16
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srl a5, a5, 8*SZREG-16
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sub a0, a4, a5
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and a1, a0, 0xff
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bnez a1, 1f
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ret
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1:and a4, a4, 0xff
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and a5, a5, 0xff
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sub a0, a4, a5
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ret
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.Lmisaligned:
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# misaligned
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lbu a2, 0(a0)
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lbu a3, 0(a1)
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add a0, a0, 1
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add a1, a1, 1
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bne a2, a3, 1f
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bnez a2, .Lmisaligned
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1:
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sub a0, a2, a3
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ret
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# cases in which a null byte was detected
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#if __riscv_xlen == 32
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foundnull 0 5
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foundnull 1 5
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foundnull 2 5
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foundnull 3 5
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foundnull 4 5
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#else
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foundnull 0 3
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foundnull 1 3
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foundnull 2 3
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#endif
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#if SZREG == 8
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.section .srodata.cst8,"aM",@progbits,8
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.align 3
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mask:
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.dword 0x7f7f7f7f7f7f7f7f
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#endif
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