ref: 600bbfe4aaa9ad0f73d8d73eef1b7670e5f7d3a3
dir: /os/pc/ptclbsum386.s/
TEXT ptclbsum(SB), $0 MOVL addr+0(FP), SI MOVL len+4(FP), CX XORL AX, AX /* sum */ TESTL $1, SI /* byte aligned? */ MOVL SI, DI JEQ _2align DECL CX JLT _return MOVB 0x00(SI), AH INCL SI _2align: TESTL $2, SI /* word aligned? */ JEQ _32loop CMPL CX, $2 /* less than 2 bytes? */ JLT _1dreg SUBL $2, CX XORL BX, BX MOVW 0x00(SI), BX ADDL BX, AX ADCL $0, AX LEAL 2(SI), SI _32loop: CMPL CX, $0x20 JLT _8loop MOVL CX, BP SHRL $5, BP ANDL $0x1F, CX _32loopx: MOVL 0x00(SI), BX MOVL 0x1C(SI), DX ADCL BX, AX MOVL 0x04(SI), BX ADCL DX, AX MOVL 0x10(SI), DX ADCL BX, AX MOVL 0x08(SI), BX ADCL DX, AX MOVL 0x14(SI), DX ADCL BX, AX MOVL 0x0C(SI), BX ADCL DX, AX MOVL 0x18(SI), DX ADCL BX, AX LEAL 0x20(SI), SI ADCL DX, AX DECL BP JNE _32loopx ADCL $0, AX _8loop: CMPL CX, $0x08 JLT _2loop MOVL CX, BP SHRL $3, BP ANDL $0x07, CX _8loopx: MOVL 0x00(SI), BX ADCL BX, AX MOVL 0x04(SI), DX ADCL DX, AX LEAL 0x08(SI), SI DECL BP JNE _8loopx ADCL $0, AX _2loop: CMPL CX, $0x02 JLT _1dreg MOVL CX, BP SHRL $1, BP ANDL $0x01, CX _2loopx: MOVWLZX 0x00(SI), BX ADCL BX, AX LEAL 0x02(SI), SI DECL BP JNE _2loopx ADCL $0, AX _1dreg: TESTL $1, CX /* 1 byte left? */ JEQ _fold XORL BX, BX MOVB 0x00(SI), BX ADDL BX, AX ADCL $0, AX _fold: MOVL AX, BX SHRL $16, BX JEQ _swab ANDL $0xFFFF, AX ADDL BX, AX JMP _fold _swab: TESTL $1, addr+0(FP) /*TESTL $1, DI*/ JNE _return XCHGB AH, AL _return: RET