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Hi, David. Spill intervals must be precolored because they can't be spilled once more. They are the shortest intervals precisely over each def/use of the original interval. That is why they also have their weights set to #INF. Imagine that on a second iteration allocation algorithm figures out that some spilled interval can't be assig...

On Monday 06 August 2007 12:15, Anton Vayvod wrote: > Spill intervals must be precolored because they can't be spilled once more. > They are the shortest intervals precisely over each def/use of the original > interval. That is why they also have their weights set to #INF. Yes, that's true. But I wonder if we shouldn't be smarter about which register we pick to colo...

On 8/7/07, David Greene <dag at cray.com> wrote: > > On Monday 06 August 2007 12:15, Anton Vayvod wrote: > > > Spill intervals must be precolored because they can't be spilled once > more. > > They are the shortest intervals precisely over each def/use of the > original > > interval. That is why they also have their weights set to #INF. > > Yes, that's true. But I wonder if we shouldn't be smarter about w...

...mentation has a flavor of it. > > In case live range splitting implemented spill intervals wouldn't have to > be the shortest when some interval is spilled the first time. But during > iterations uncolored spill intervals should become shorter and shorter > until they are must-be-precolored. Right, except for the pre-coloring bit. :) > As far as I understand, you don't need to call spiller every iteration. Right, that was my fundamental misunderstanding. I've got it straight now. Thanks to everyone for the help. -Dave

Can someone explain the theory behind the spillers in VirtRegMap.cpp? It seems as though the spillers do triple duty: - Insert load/store operations and/or fold instructions as necessary to carry out spills - Rewrite the spilled virtual registers to use machine registers (mapping given by the caller in the VRM). - Rewrite machine code to change virtual registers to physical registers

> > FYI, in my implementation I just marked the intervals introduced by > spills as being special so that they would not be chosen to be spilled > again. Then they just get colored like every other interval. But they can be uncolored like every other interval then, right? When your algorithm finds out during one iteration that it should spill some interval it checks whether this

On Mon, 6 Aug 2007, David Greene wrote: >> split into smth like [10, 40) and [40, 50). The former part should not be >> precolored as it has less conflicts (it doesn't intersects with [40, 45) ) >> and can be colored entirely by one register on the next iteration. > > Right. Live range splitting would indeed be nice to have. Bill's > implementation has a flavor of it. > >> Unfortunately, it s...

For spilling, I plan to use the Hack-Braun generalization of the furthest-first heuristic for SSA: http://pp.info.uni-karlsruhe.de/uploads/publikationen/braun09cc.pdf For coloring, there are a few different approaches you can take, e.g. dominator tree scan, puzzle-solving, or a modified graph coloring / coalescing heuristic like IRC. The best quality for the least amount of implementation effort

The allocator you are building, is it the Hack's and Goos's polynomial time algorithm? On Tue, Oct 5, 2010 at 7:14 PM, Cameron Zwarich <zwarich at apple.com> wrote: > There is nothing that currently handles this properly, as far as I know. If you have a phi > > c = phi(a, b) > > where a, b and c are all assigned distinct stack slots, then copies must be inserted in