What is the defference between movd and movss?

Dear all,

movd is to move 32-bit interger to xmm register.
movss is to to 32-bit floating float instead.

however, would:

movd  xmm0, DWORD PTR[eax]
movss  xmm0, DWORD PTR[eax]

be the same? Or this there a difference in speed?

Thank you.
hengck23Asked:
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dimitryCommented:
These are same commands according to Intel spec:
MOVD instruction when destination operand is XMM register:
DEST[31-0] ←SRC;
DEST[127-32] ←000000000000000000000000H;

MOVSS instruction when source operand is memory location and destination operand is XMM register:
DEST[31-0] ←SRC;
DEST[127-32] ←000000000000000000000000H;

However they have different C/C++ Intel Compiler Intrinsics...
Despite I think there is no speed difference, I would suggest to use movss as special SSE command.


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dimitryCommented:
&#8592; supposes to mean <-
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srini_vcCommented:
no-         movd moves 64 bit data not 32 bit
movss is not there in 80x86 instruction set.     movs is there but it's used for moving string. i thought, i'm correct?


byte                               (MOVB 8 bits),
word                              (MOVW 16 bits),
longword                        (MOVL 32 bits),
quadword                       (MOVQ 64 bits),
octaword                        (MOVQ 128 bits),
single precision floating    (MOVF 32 bits),
double precision floating   (MOVD 64 bits),
G floating                        (MOVG 64 bits), or
H floating                        (MOVH 128 bits)


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mbizupCommented:
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I will leave the following recommendation for this question in the Cleanup topic area:
    Accept: dimitry {http:#12547124}

Any objections should be posted here in the next 4 days. After that time, the question will be closed.

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