On Tue, Mar 31, 2020 at 4:05 PM John Naylor <john.nay...@2ndquadrant.com> wrote: > > On Tue, Mar 31, 2020 at 2:31 AM Andres Freund <and...@anarazel.de> wrote: > > I think the form of lea generated here is among the ones that can only > > be executed on port 1. Whereas e.g. an register+register/immediate add > > can be executed on four different ports. > > I looked into slow vs. fast leas, and I think the above are actually > fast because they have 2 operands.
No, scratch that, it seems the two forms of lea are: leal (,%rdx,8), %ecx leal (%rdx,%rdx,8), %ecx The first operand in both is the implicit zero, so with 3 and 5 we do get the slow lea on some architectures. So I've only kept the shift-and-add multipliers in v2. I also changed the order of iteration of the parameters, for speed. Before, it took over 30 seconds to build the unicode quick check tables, now it takes under 2 seconds. -- John Naylor https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
v2-tweak-perfect-hash-gen.patch
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