On Tue, Jun 2, 2009 at 4:46 PM, Sven Neumann <sven@xxxxxxxx> wrote: > Hi, > > first of all thanks a lot for providing these patches. I definitely want > to get them merged as soon as possible. But there are a few minor issues > that should be discussed first. So let me start by commenting on your > first patch: > > On Tue, 2009-06-02 at 04:11 -0400, Christopher Montgomery wrote: >> #define TILE_DATA_POINTER(tile,x,y) \ >> ((tile)->data + \ >> - (((y) % TILE_HEIGHT) * (tile)->ewidth + ((x) % TILE_WIDTH)) * >> (tile)->bpp) >> - >> + (((y) & (TILE_HEIGHT-1)) * (tile)->ewidth + ((x) & >> (TILE_WIDTH-1))) * (tile)->bpp) > > As far as I know pretty much any compiler out there should be able to > replace a modulo by a power-of-2 constant by the bit-wise AND operation > without us explicitly doing so (see also > http://en.wikipedia.org/wiki/Modulo_operation#Performance_issues). So > for the benefit of readable code I suggest that we keep the code as it > is. Interesting. I got a noticable and repeatable performance benefit. Which is not to say I haven't somehow mismeasured it. I agree the modulo is more readable. ...perhaps the difference is the difference of (x) or (y) possibly being negative and additional conformance-related assembly getting generated? I suppose there's no reason to speculate, I'll go read the assembly gcc generates and that will answer everything, at least for me. Monty _______________________________________________ Gimp-developer mailing list Gimp-developer@xxxxxxxxxxxxxxxxxxxxxx https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
