In the DMD code generator I believe the modrm reg and rm bits are being
interpreted the wrong way round for this instruction.
Consider this assembly code:
asm
{
movd ECX, XMM0;
movd ECX, XMM1;
movd ECX, XMM2;
movd ECX, XMM3;
movd ECX, XMM4;
movd ECX, XMM5;
movd ECX, XMM6;
movd ECX, XMM7;
}
In visual C++ 2005 express (and my own calculations) produces the following
machine code:
66 0f 7e c1 ;movd ecx, xmm0
66 0f 7e c9 ;movd ecx, xmm1
66 0f 7e d1 ;movd ecx, xmm2
66 0f 7e d9 ;movd ecx, xmm3
66 0f 7e e1 ;movd ecx, xmm4
66 0f 7e e9 ;movd ecx, xmm5
66 0f 7e f1 ;movd ecx, xmm6
66 0f 7e f9 ;movd ecx, xmm7
In DMD 0.149 it produces this:
66 0F 7E C8 ;movd EAX, XMM1
66 0F 7E C9 ;movd ECX, XMM1
66 0F 7E CA ;movd EDX, XMM1
66 0F 7E CB ;movd EBX, XMM1
66 0F 7E CC ;movd ESP, XMM1
66 0F 7E CD ;movd EBP, XMM1
66 0F 7E CE ;movd ESI, XMM1
66 0F 7E CF ;movd EDI, XMM1
----------------------------------------
And this assembly code:
asm
{
movd EAX, XMM0;
movd ECX, XMM0;
movd EDX, XMM0;
movd EBX, XMM0;
movd ESI, XMM0;
movd EDI, XMM0;
movd EBP, XMM0;
movd ESI, XMM0;
}
In Visual C++ 2005 Express (and my own calculations) produces this machine code:
66 0f 7e c0 ;movd eax, xmm0
66 0f 7e c1 ;movd ecx, xmm0
66 0f 7e c2 ;movd edx, xmm0
66 0f 7e c3 ;movd ebx, xmm0
66 0f 7e c6 ;movd esi, xmm0
66 0f 7e c7 ;movd edi, xmm0
66 0f 7e c5 ;movd ebp, xmm0
66 0f 7e c6 ;movd esi, xmm0
In DMD 0.149 it produces this:
66 0F 7E C0 ;movd EAX, XMM0
66 0F 7E C8 ;movd EAX, XMM1
66 0F 7E D0 ;movd EAX, XMM2
66 0F 7E D8 ;movd EAX, XMM3
66 0F 7E F0 ;movd EAX, XMM6
66 0F 7E F8 ;movd EAX, XMM7
66 0F 7E E8 ;movd EAX, XMM5
66 0F 7E F0 ;movd EAX, XMM6
Interestingly, if you just use the EAX register then it works ok eg.
This assembly:
asm
{
movd EAX, XMM1;
movd EAX, XMM2;
movd EAX, XMM3;
movd EAX, XMM4;
movd EAX, XMM5;
movd EAX, XMM6;
movd EAX, XMM7;
}
Produces this which is correct:
66 0F 7E C0 ;movd EAX, XMM0
66 0F 7E C8 ;movd EAX, XMM1
66 0F 7E D0 ;movd EAX, XMM2
66 0F 7E D8 ;movd EAX, XMM3
66 0F 7E E0 ;movd EAX, XMM4
66 0F 7E E8 ;movd EAX, XMM5
66 0F 7E F0 ;movd EAX, XMM6
66 0F 7E F8 ;movd EAX, XMM7
-------------------------------------------
Proof:
import std.stdio;
int main(char[][] args)
{
asm
{
// make sure XMM1 is not 0
mov EAX,1;
movd XMM1, EAX; // moving from reg32 to XMM works ok
mov EAX,0; // ok EAX is now 0
// here is the test
// we move XMM0 to the ECX register
// (EAX should be in no way affected by this)
movd ECX, XMM0; // actual instruction executed will be movd EAX,XMM1;
// right let's look at EAX now
cmp EAX,0;
je good;
// oh dear
}
writefln("EAX is not 0. We have a problem.");
return 1;
good:
writefln("EAX = 0. Everything is alright with the world");
return 0;
}
I assume that as DMD and DMC use the same backend then this bug also affects
DMC.
Regards,
pmoore