out method and method with return value

=?Utf-8?B?bGlhbnF0bGl0?=

In performance wise which is more costly to use when there one value to return?
Is it the out method parameter or the method that has a return value?

Dec 19 '07 #1

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Michael C

"lianqtlit" <li*******@disc ussions.microso ft.comwrote in message
news:83******** *************** ***********@mic rosoft.com...

In performance wise which is more costly to use when there one value to
return?
Is it the out method parameter or the method that has a return value?

Return value I presume. In most languages the return value is returned in a
register whereas a parameter is placed on the stack.

>

Dec 19 '07 #2

=?UTF-8?B?QXJuZSBWYWpow7hq?=

lianqtlit wrote:

In performance wise which is more costly to use when there one value to return?
Is it the out method parameter or the method that has a return value?

It is extremely unlikely that the difference will have any impact on
your overall performance.

Focus on readable code instead of "nanosecond s performance tuning".

Arne

Dec 19 '07 #3

=?ISO-8859-1?Q?Arne_Vajh=F8j?=

Michael C wrote:

"lianqtlit" <li*******@disc ussions.microso ft.comwrote in message
news:83******** *************** ***********@mic rosoft.com...
>In performance wise which is more costly to use when there one value to
return?
Is it the out method parameter or the method that has a return value?

Return value I presume. In most languages the return value is returned in a
register whereas a parameter is placed on the stack.

Did you read it as "more efficient" or do you think register is slower
than stack ?

Arne

Dec 19 '07 #4

Michael C

"Arne Vajhøj" <ar**@vajhoej.d kwrote in message
news:47******** *************** @news.sunsite.d k...

Did you read it as "more efficient" or do you think register is slower
than stack ?

Sorry, I misread what the OP said. I think the register will be faster and
more efficient.

Michael

Dec 19 '07 #5

Willy Denoyette [MVP]

"lianqtlit" <li*******@disc ussions.microso ft.comwrote in message
news:83******** *************** ***********@mic rosoft.com...

In performance wise which is more costly to use when there one value to
return?
Is it the out method parameter or the method that has a return value?

You should definitely not care about this, chances are that the method is
inlined, and if not, the (single) argument is passed in a register too.
Managed code uses the "CLR calling" convention when running on X86, that is,
it passes the first two arguments in a register. The 'this' pointer is
passed in 'ecx' while the "first" argument is passed in 'esi'. More, when
running on X64 in 64-bit mode, the first four arguments are passed in a
register, so here you have even less reasons to care about argument passing
efficiency.

Willy.

Dec 19 '07 #6

Ben Voigt [C++ MVP]

"Willy Denoyette [MVP]" <wi************ *@telenet.bewro te in message
news:e3******** ******@TK2MSFTN GP05.phx.gbl...

"lianqtlit" <li*******@disc ussions.microso ft.comwrote in message
news:83******** *************** ***********@mic rosoft.com...
>In performance wise which is more costly to use when there one value to
return?
Is it the out method parameter or the method that has a return value?

You should definitely not care about this, chances are that the method is
inlined, and if not, the (single) argument is passed in a register too.

out arguments have to be passed by address... unless inlined

Just make sure the function is inlined.

As a side note, the out parameter can use type inference, the return type
can't (except for op_Implicit and op_Explicit).

Dec 19 '07 #7

Willy Denoyette [MVP]

"Ben Voigt [C++ MVP]" <rb*@nospam.nos pamwrote in message
news:uW******** ******@TK2MSFTN GP04.phx.gbl...

>
"Willy Denoyette [MVP]" <wi************ *@telenet.bewro te in message
news:e3******** ******@TK2MSFTN GP05.phx.gbl...
>"lianqtlit" <li*******@disc ussions.microso ft.comwrote in message
news:83******* *************** ************@mi crosoft.com...
>>In performance wise which is more costly to use when there one value to
return?
Is it the out method parameter or the method that has a return value?

You should definitely not care about this, chances are that the method is
inlined, and if not, the (single) argument is passed in a register too.

out arguments have to be passed by address... unless inlined

Yep, sorry for the confusion, what I meant was that a single argument is
passed in a register, not on the stack.
What is returned is also placed in a register (by convention eax on X86), be
it an address or a value

Just make sure the function is inlined.

You don't have control over this, it's the JIT who decides what will be
inlined.

As a side note, the out parameter can use type inference, the return type
can't (except for op_Implicit and op_Explicit).

Agreed.

Willy.

Dec 20 '07 #8

Michael C

"Willy Denoyette [MVP]" <wi************ *@telenet.bewro te in message
news:e3******** ******@TK2MSFTN GP05.phx.gbl...

You should definitely not care about this, chances are

Chances are much improved (to certainty) that the return value will be in a
register if it is not a parameter. :-)

Michael

Dec 20 '07 #9

Willy Denoyette [MVP]

"Michael C" <mi**@nospam.co mwrote in message
news:u$******** ******@TK2MSFTN GP04.phx.gbl...

"Willy Denoyette [MVP]" <wi************ *@telenet.bewro te in message
news:e3******** ******@TK2MSFTN GP05.phx.gbl...
>You should definitely not care about this, chances are

Chances are much improved (to certainty) that the return value will be in
a register if it is not a parameter. :-)

Michael

Sure, on X86 return values can even occupy two registers, a long or a double
return value for instance are returned in 'eax' and 'edx'. Note that I'm
absolutely not promoting passing ByRef values, this is a matter of the
semantic requirements, all I'm trying to say is that the JIT32 uses a
calling sequence which allows you to pass single argument (plus the this
pointer) in a register.

Willy.

Dec 20 '07 #10

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