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+ added an i8086 asm optimized version of CompareByte()

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git-svn-id: trunk@32026 -
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nickysn 2015-10-12 16:47:50 +00:00
parent 385f0d4ee8
commit f107956169
1 changed files with 57 additions and 0 deletions
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57
rtl/i8086/i8086.inc
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@ -273,6 +273,63 @@ end;
{$endif FPC_SYSTEM_HAS_INDEXDWORD}
{$ifndef FPC_SYSTEM_HAS_COMPAREBYTE}
{$define FPC_SYSTEM_HAS_COMPAREBYTE}
function CompareByte(Const buf1,buf2;len:SizeInt):SizeInt; assembler; nostackframe;
asm
xor ax, ax // initialize ax=0 (it's the result register, we never use it for anything else in this function)
mov bx, sp
mov cx, ss:[bx + 2 + extra_param_offset] // len
mov dx, ds // for far data models, backup ds; for near data models, use to initialize es
or cx, cx
jz @@Equal
{$ifdef FPC_X86_DATA_NEAR}
mov es, dx
mov si, ss:[bx + 6 + extra_param_offset] // @buf1
mov di, ss:[bx + 4 + extra_param_offset] // @buf2
{$else FPC_X86_DATA_NEAR}
lds si, ss:[bx + 8 + extra_param_offset] // @buf1
les di, ss:[bx + 4 + extra_param_offset] // @buf2
{$endif FPC_X86_DATA_NEAR}
{$ifdef FPC_ENABLED_CLD}
cld
{$endif FPC_ENABLED_CLD}
xor bx, bx
shr cx, 1
adc bx, bx // remainder goes to bx
jcxz @@BytewiseComparison
repe cmpsw
je @@BytewiseComparison
// we found an unequal word
// let's go back and compare it bytewise
mov bl, 2
dec si
dec si
dec di
dec di
@@BytewiseComparison:
mov cx, bx
jcxz @@Equal
repe cmpsb
je @@Equal
// ax is 0
sbb ax, ax
shl ax, 1
inc ax
@@Equal:
// ax is 0
@@Done:
{$if defined(FPC_X86_DATA_FAR) or defined(FPC_X86_DATA_HUGE)}
mov ds, dx
{$endif}
end;
{$endif FPC_SYSTEM_HAS_COMPAREBYTE}
{$define FPC_SYSTEM_HAS_SPTR}
Function Sptr : Pointer;assembler;nostackframe;
asm