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@@ -0,0 +1,140 @@
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+{
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+ $Id$
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+ This file is part of the Free Pascal run time library.
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+ Copyright (c) 1999-2000 by the Free Pascal development team
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+
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+ Processor specific implementation of strlen
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+
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+ See the file COPYING.FPC, included in this distribution,
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+ for details about the copyright.
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+
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+ This program is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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+
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+ **********************************************************************}
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+{
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+ Implemented using the code from glibc: libc/sysdeps/x86_64/strlen.S Version 1.2
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+}
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+asm
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+ movq %rdi, %rcx { Duplicate source pointer. }
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+ andl $7, %ecx { mask alignment bits }
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+ movq %rdi, %rax { duplicate destination. }
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+ jz LFPC_STRLEN_1 { aligned => start loop }
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+
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+ neg %ecx { We need to align to 8 bytes. }
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+ addl $8,%ecx
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+ { Search the first bytes directly. }
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+LFPC_STRLEN_0:
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+ cmpb $0x0,(%rax) { is byte NUL? }
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+ je LFPC_STRLEN_2 { yes => return }
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+ incq %rax { increment pointer }
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+ decl %ecx
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+ jnz LFPC_STRLEN_0
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+
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+LFPC_STRLEN_1:
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+ movq $0xfefefefefefefeff,%r8 { Save magic. }
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+
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+ .p2align 4 { Align loop. }
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+LFPC_STRLEN_4: { Main Loop is unrolled 4 times. }
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+ { First unroll. }
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+ movq (%rax), %rcx { get double word (= 8 bytes) in question }
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+ addq $8,%rax { adjust pointer for next word }
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+ movq %r8, %rdx { magic value }
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+ addq %rcx, %rdx { add the magic value to the word. We get
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+ carry bits reported for each byte which
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+ is *not* 0 }
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+ jnc LFPC_STRLEN_3 { highest byte is NUL => return pointer }
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+ xorq %rcx, %rdx { (word+magic)^word }
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+ orq %r8, %rdx { set all non-carry bits }
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+ incq %rdx { add 1: if one carry bit was *not* set
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+ the addition will not result in 0. }
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+ jnz LFPC_STRLEN_3 { found NUL => return pointer }
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+
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+ { Second unroll. }
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+ movq (%rax), %rcx { get double word (= 8 bytes) in question }
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+ addq $8,%rax { adjust pointer for next word }
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+ movq %r8, %rdx { magic value }
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+ addq %rcx, %rdx { add the magic value to the word. We get
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+ carry bits reported for each byte which
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+ is *not* 0 }
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+ jnc LFPC_STRLEN_3 { highest byte is NUL => return pointer }
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+ xorq %rcx, %rdx { (word+magic)^word }
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+ orq %r8, %rdx { set all non-carry bits }
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+ incq %rdx { add 1: if one carry bit was *not* set
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+ the addition will not result in 0. }
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+ jnz LFPC_STRLEN_3 { found NUL => return pointer }
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+
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+ { Third unroll. }
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+ movq (%rax), %rcx { get double word (= 8 bytes) in question }
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+ addq $8,%rax { adjust pointer for next word }
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+ movq %r8, %rdx { magic value }
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+ addq %rcx, %rdx { add the magic value to the word. We get
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+ carry bits reported for each byte which
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+ is *not* 0 }
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+ jnc LFPC_STRLEN_3 { highest byte is NUL => return pointer }
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+ xorq %rcx, %rdx { (word+magic)^word }
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+ orq %r8, %rdx { set all non-carry bits }
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+ incq %rdx { add 1: if one carry bit was *not* set
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+ the addition will not result in 0. }
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+ jnz LFPC_STRLEN_3 { found NUL => return pointer }
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+
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+ { Fourth unroll. }
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+ movq (%rax), %rcx { get double word (= 8 bytes) in question }
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+ addq $8,%rax { adjust pointer for next word }
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+ movq %r8, %rdx { magic value }
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+ addq %rcx, %rdx { add the magic value to the word. We get
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+ carry bits reported for each byte which
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+ is *not* 0 }
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+ jnc LFPC_STRLEN_3 { highest byte is NUL => return pointer }
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+ xorq %rcx, %rdx { (word+magic)^word }
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+ orq %r8, %rdx { set all non-carry bits }
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+ incq %rdx { add 1: if one carry bit was *not* set
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+ the addition will not result in 0. }
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+ jz LFPC_STRLEN_4 { no NUL found => continue loop }
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+
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+ .p2align 4 { Align, it's a jump target. }
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+LFPC_STRLEN_3:
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+ subq $8,%rax { correct pointer increment. }
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+
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+ testb %cl, %cl { is first byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return }
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+ incq %rax { increment pointer }
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+
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+ testb %ch, %ch { is second byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return }
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+ incq %rax { increment pointer }
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+
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+ testl $0x00ff0000, %ecx { is third byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return pointer }
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+ incq %rax { increment pointer }
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+
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+ testl $0xff000000, %ecx { is fourth byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return pointer }
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+ incq %rax { increment pointer }
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+
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+ shrq $32, %rcx { look at other half. }
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+
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+ testb %cl, %cl { is first byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return }
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+ incq %rax { increment pointer }
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+
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+ testb %ch, %ch { is second byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return }
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+ incq %rax { increment pointer }
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+
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+ testl $0xff0000, %ecx { is third byte NUL? }
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+ jz LFPC_STRLEN_2 { yes => return pointer }
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+ incq %rax { increment pointer }
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+LFPC_STRLEN_2:
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+ subq %rdi, %rax { compute difference to string start }
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+ ret
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+end;
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+
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+
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+{
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+ $Log$
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+ Revision 1.1 2003-04-30 16:36:39 florian
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+ + support for generic pchar routines added
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+ + some basic rtl stuff for x86-64 added
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+}
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florian