关于c ++：在汇编代码中寻找不必要的缓冲区副本

Looking for unnecessary buffer copies in assembly code

我正在将Visual Studio 2008 C ++用于Windows Mobile 6 ARMV4I，并且正在尝试学习阅读VS生成的ARM汇编代码，以最大程度地减少应用程序内不必要的缓冲区副本。因此，我创建了一个如下所示的测试应用程序：

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#include <vector>

typedef std::vector< BYTE > Buf;

class Foo
{
public:
Foo( Buf b ) { b_.swap( b ); };
private:
Buf b_;
};

Buf Create()
{
Buf b( 1024 );
b[ 0 ] = 0x0001;
return b;
}

int _tmain( int argc, _TCHAR* argv[] )
{
Foo f( Create() );
return 0;
}

我想了解在将Create返回的缓冲区提供给Foo构造函数时是否已复制，或者编译器是否能够优化该副本。在启用了优化的Release版本中，将生成如下所示的程序集：

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class Foo
{
public:
Foo( Buf b ) { b_.swap( b ); };
0001112C stmdb sp!, {r4 - r7, lr}
00011130 mov r7, r0
00011134 mov r3, #0
00011138 str r3, this
0001113C str r3, [r7, #4]
00011140 str r3, [r7, #8]
00011144 ldr r3, this
00011148 ldr r2, this
0001114C mov r5, r7
00011150 mov r4, r1
00011154 str r3, this, #4
00011158 str r2, this, #4
0001115C mov r6, r1
00011160 ldr r2, this
00011164 ldr r3, this
00011168 mov lr, r7
0001116C str r3, this
00011170 str r2, this
00011174 ldr r2, [lr, #8]!
00011178 ldr r3, [r6, #8]!
0001117C str r3, this
00011180 str r2, this
00011184 ldr r3, this
00011188 movs r0, r3
0001118C beq |Foo::Foo + 0x84 ( 111b0h )|
00011190 ldr r3, [r1, #8]
00011194 sub r1, r3, r0
00011198 cmp r1, #0x80
0001119C bls |Foo::Foo + 0x80 ( 111ach )|
000111A0 bl 000112D4
000111A4 mov r0, r7
000111A8 ldmia sp!, {r4 - r7, pc}
000111AC bl |stlp_std::__node_alloc::_M_deallocate ( 11d2ch )|
000111B0 mov r0, r7
000111B4 ldmia sp!, {r4 - r7, pc}
--- ...\stlport\stl\_vector.h -----------------------------
// snip!
--- ...\asm_test.cpp
private:
Buf b_;
};

Buf Create()
{
00011240 stmdb sp!, {r4, lr}
00011244 mov r4, r0
Buf b( 1024 );
00011248 mov r1, #1, 22
0001124C bl |
b[ 0 ] = 0x0001;
00011250 ldr r3, [r4]
00011254 mov r2, #1
return b;
}

int _tmain( int argc, _TCHAR* argv[] )
{
00011264 str lr, [sp, #-4]!
00011268 sub sp, sp, #0x18
Foo f( Create() );
0001126C add r0, sp, #0xC
00011270 bl |Create ( 11240h )|
00011274 mov r1, r0
00011278 add r0, sp, #0
0001127C bl |Foo::Foo ( 1112ch )|
return 0;
00011280 ldr r0, argc
00011284 cmp r0, #0
00011288 beq |wmain + 0x44 ( 112a8h )|
0001128C ldr r3, [sp, #8]
00011290 sub r1, r3, r0
00011294 cmp r1, #0x80
00011298 bls |wmain + 0x40 ( 112a4h )|
0001129C bl 000112D4
000112A0 b |wmain + 0x44 ( 112a8h )|
000112A4 bl |stlp_std::__node_alloc::_M_deallocate ( 11d2ch )|
000112A8 mov r0, #0
}

我可以在汇编代码中寻找什么模式来了解Buf结构的复制位置？