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Subject: Re: Branchless code

Author: Robert Hyatt

Date: 11:40:50 11/19/02

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On November 19, 2002 at 04:41:59, Gunnar Andersson wrote:

>On November 18, 2002 at 20:09:27, Eugene Nalimov wrote:
>
>>Indirect call costs *at least* the same as conditional branch, sometimes much
>>more.
>
>I've discovered that arrays of function pointers can outperform switch
>statements, at least with GCC and many cases.  To me the generated assembly code
>for the switch statement contains a jump table anyway, and there's some extra
>assembly code essentially performing range checking.
>
>/ Gunnar


It would be interesting to look at the .s file from gcc to see what it is doing.
 The
indirect calls should be bad.  Of course the range checking in a switch is also
bad,
but I have seen compilers that would let me turn this off...

• Re: Branchless code Eugene Nalimov 13:29:41 11/19/02
  • Re: Branchless code Robert Hyatt 13:41:11 11/19/02
    • Re: Branchless code Eugene Nalimov 14:11:33 11/19/02
      • ASM masters: here another related question Dezhi Zhao 20:10:15 11/19/02
      • Re: Branchless code Robert Hyatt 15:08:59 11/19/02

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