windows - Delphi 10.2 for Win64 Release Target 下的 FillChar 和 StringOfChar

Question

我对 Delphi 10.2 Pascal 编程语言中的特定编程问题有疑问。

StringOfChar 和 FillChar 在 2012 年之前发布的 CPU 上的 Win64 版本构建下无法正常工作。

• FillChar 的预期结果只是在给定内存缓冲区中重复 8 位字符的普通序列。

• StringOfChar 的预期结果相同，但结果存储在字符串类型中。

但实际上，当我使用 10.2 版本的 Delphi 编译在 10.2 之前的 Delphi 中运行的应用程序时，我们为 Win64 编译的应用程序在 2012 年之前发布的 CPU 上无法正常运行。

StringOfChar 和 FillChar 不能正常工作——它们返回一个由不同字符组成的字符串，尽管是重复的模式——而不是它们应该返回的相同字符的序列。

这是足以说明问题的最少代码。请注意，序列的长度应至少为 16 个字符，且字符不应为 nul (#0)。代码如下:

procedure TestStringOfChar;
var
  a: AnsiString;
  ac: AnsiChar;
begin
  ac := #1;
  a := StringOfChar(ac, 43);
  if a <> #1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1#1 then
  begin
    raise Exception.Create('ANSI StringOfChar Failed!!');
  end;
end;

我知道 StackOverflow 上有很多 Delphi 程序员。您遇到同样的问题吗？如果是，你是如何解决的？解决办法是什么？顺便说一下，I have contacted the developers of Delphi but they didn’t confirm nor deny the issue so far .我使用的是 Embarcadero Delphi 10.2 版本 25.0.26309.314。

更新:

如果您的 CPU 是 2012 年或之后生产的，请在调用 StringOfChar 重现问题之前添加以下行:

const
  ERMSBBit    = 1 shl 9; //$0200
begin
  CPUIDTable[7].EBX := CPUIDTable[7].EBX and not ERMSBBit;

关于April 2017 RAD Studio 10.2 Hotfix for Toolchain Issues - 尝试过使用它和不使用它 - 它没有帮助。无论修补程序如何，该问题都存在。

更新#2

Embarcadero 已于 08/Aug/17 下午 6:03 确认并解决了此问题。因此，在 Delphi 10.2 Tokyo Release 1(2017 年 8 月 8 日发布)中修复了此错误。

Answer 1

StringOfChar(A: AnsiChar, count) 在底层使用 FillChar。

您可以使用以下代码来解决问题:

(*******************************************************
 System.FastSystem
 A fast drop-in addition to speed up function in system.pas
 It should compile and run in XE2 and beyond.
 Alpha version 0.5, fully tested in Win64
 (c) Copyright 2016 J. Bontes
   This Source Code Form is subject to the terms of the
   Mozilla Public License, v. 2.0.
   If a copy of the MPL was not distributed with this file,
   You can obtain one at http://mozilla.org/MPL/2.0/.
********************************************************
FillChar code is an altered version FillCharsse2 SynCommons.pas
which is part of Synopse framework by Arnaud Bouchez
********************************************************
Changelog
0.5 Initial version:
********************************************************)

unit FastSystem;

interface

procedure FillChar(var Dest; Count: NativeInt; Value: ansichar); inline; overload;
procedure FillChar(var Dest; Count: NativeInt; Value: Byte); overload;
procedure FillMemory(Destination: Pointer; Length: NativeUInt; Fill: Byte); inline;
{$EXTERNALSYM FillMemory}
procedure ZeroMemory(Destination: Pointer; Length: NativeUInt); inline;
{$EXTERNALSYM ZeroMemory}

implementation

procedure FillChar(var Dest; Count: NativeInt; Value: ansichar); inline; overload;
begin
  FillChar(Dest, Count, byte(Value));
end;

procedure FillMemory(Destination: Pointer; Length: NativeUInt; Fill: Byte);
begin
  FillChar(Destination^, Length, Fill);
end;

procedure ZeroMemory(Destination: Pointer; Length: NativeUInt); inline;
begin
  FillChar(Destination^, Length, 0);
end;

//This code is 3x faster than System.FillChar on x64.

{$ifdef CPUX64}
procedure FillChar(var Dest; Count: NativeInt; Value: Byte);
//rcx = dest
//rdx=count
//r8b=value
asm
              .noframe
              .align 16
              movzx r8,r8b           //There's no need to optimize for count <= 3
              mov rax,$0101010101010101
              mov r9d,edx
              imul rax,r8            //fill rax with value.
              cmp rdx,59             //Use simple code for small blocks.
              jl  @Below32
@Above32:     mov r11,rcx
              mov r8b,7              //code shrink to help alignment.
              lea r9,[rcx+rdx]       //r9=end of array
              sub rdx,8
              rep mov [rcx],rax
              add rcx,8
              and r11,r8             //and 7 See if dest is aligned
              jz @tail
@NotAligned:  xor rcx,r11            //align dest
              lea rdx,[rdx+r11]
@tail:        test r9,r8             //and 7 is tail aligned?
              jz @alignOK
@tailwrite:   mov [r9-8],rax         //no, we need to do a tail write
              and r9,r8              //and 7
              sub rdx,r9             //dec(count, tailcount)
@alignOK:     mov r10,rdx
              and edx,(32+16+8)      //count the partial iterations of the loop
              mov r8b,64             //code shrink to help alignment.
              mov r9,rdx
              jz @Initloop64
@partialloop: shr r9,1              //every instruction is 4 bytes
              lea r11,[rip + @partial +(4*7)] //start at the end of the loop
              sub r11,r9            //step back as needed
              add rcx,rdx            //add the partial loop count to dest
              cmp r10,r8             //do we need to do more loops?
              jmp r11                //do a partial loop
@Initloop64:  shr r10,6              //any work left?
              jz @done               //no, return
              mov rdx,r10
              shr r10,(19-6)         //use non-temporal move for > 512kb
              jnz @InitFillHuge
@Doloop64:    add rcx,r8
              dec edx
              mov [rcx-64+00H],rax
              mov [rcx-64+08H],rax
              mov [rcx-64+10H],rax
              mov [rcx-64+18H],rax
              mov [rcx-64+20H],rax
              mov [rcx-64+28H],rax
              mov [rcx-64+30H],rax
              mov [rcx-64+38H],rax
              jnz @DoLoop64
@done:        rep ret
              //db $66,$66,$0f,$1f,$44,$00,$00 //nop7
@partial:     mov [rcx-64+08H],rax
              mov [rcx-64+10H],rax
              mov [rcx-64+18H],rax
              mov [rcx-64+20H],rax
              mov [rcx-64+28H],rax
              mov [rcx-64+30H],rax
              mov [rcx-64+38H],rax
              jge @Initloop64        //are we done with all loops?
              rep ret
              db $0F,$1F,$40,$00
@InitFillHuge:
@FillHuge:    add rcx,r8
              dec rdx
              db $48,$0F,$C3,$41,$C0 // movnti  [rcx-64+00H],rax
              db $48,$0F,$C3,$41,$C8 // movnti  [rcx-64+08H],rax
              db $48,$0F,$C3,$41,$D0 // movnti  [rcx-64+10H],rax
              db $48,$0F,$C3,$41,$D8 // movnti  [rcx-64+18H],rax
              db $48,$0F,$C3,$41,$E0 // movnti  [rcx-64+20H],rax
              db $48,$0F,$C3,$41,$E8 // movnti  [rcx-64+28H],rax
              db $48,$0F,$C3,$41,$F0 // movnti  [rcx-64+30H],rax
              db $48,$0F,$C3,$41,$F8 // movnti  [rcx-64+38H],rax
              jnz @FillHuge
@donefillhuge:mfence
              rep ret
              db $0F,$1F,$44,$00,$00  //db $0F,$1F,$40,$00
@Below32:     and  r9d,not(3)
              jz @SizeIs3
@FillTail:    sub   edx,4
              lea   r10,[rip + @SmallFill + (15*4)]
              sub   r10,r9
              jmp   r10
@SmallFill:   rep mov [rcx+56], eax
              rep mov [rcx+52], eax
              rep mov [rcx+48], eax
              rep mov [rcx+44], eax
              rep mov [rcx+40], eax
              rep mov [rcx+36], eax
              rep mov [rcx+32], eax
              rep mov [rcx+28], eax
              rep mov [rcx+24], eax
              rep mov [rcx+20], eax
              rep mov [rcx+16], eax
              rep mov [rcx+12], eax
              rep mov [rcx+08], eax
              rep mov [rcx+04], eax
              mov [rcx],eax
@Fallthough:  mov [rcx+rdx],eax  //unaligned write to fix up tail
              rep ret

@SizeIs3:     shl edx,2           //r9 <= 3  r9*4
              lea r10,[rip + @do3 + (4*3)]
              sub r10,rdx
              jmp r10
@do3:         rep mov [rcx+2],al
@do2:         mov [rcx],ax
              ret
@do1:         mov [rcx],al
              rep ret
@do0:         rep ret
end;
{$endif}

解决问题的最简单方法是 Download Mormot并包括 SynCommon.pas进入你的项目。这会将 System.FillChar 修补到上述代码，并包括一些其他性能改进。

请注意，您不需要所有的 Mormot，只需要 SynCommons 本身。