search for: fusable

...which instructions can be fused. The Sandy Bridge processors fuse more pairs than previous generations, but the second instruction is always a conditional branch. There is no need to define pseudo-instructions to support this. If you want to experiment, you could add a late pass that tries to form fusable pairs by pushing instructions down to the conditional branch. This should happen after register allocation where code is often inserted before a branch. I would be interested to see the performance impact of such a pass. /jakob

...enumerating the possible pairings can > be done in a sub-quadratic way, but I will do some profiling and see if > I can make things better. To be fair, this test creates a kind of a > worse-case scenario: an increasingly large block of instructions, almost > all of which are potentially fusable. > > It may also be possible to design additional heuristics to help the > situation. For example, we might introduce a target chain length such > that if the vectorizer finds a chain of a given length, it selects it, > foregoing the remainder of the search for the selected starting...

On Sat, 2011-10-29 at 14:02 -0500, Hal Finkel wrote: > On Sat, 2011-10-29 at 12:30 -0500, Hal Finkel wrote: > > Ralf, et al., > > > > Attached is the latest version of my autovectorization patch. llvmdev > > has been CC'd (as had been suggested to me); this e-mail contains > > additional benchmark results. > > > > First, these are preliminary