[PATCH] D120752: [RegAlloc] Add a complexity limit in growRegion() to cap compilation time.

[Mircea Trofin via Phabricator via llvm-commits]

mtrofin accepted this revision.
mtrofin added a comment.
This revision is now accepted and ready to land.

Nit: can you please rephrase the commit message, last statement: the patch (correctly) doesn't place a limit on time (which would be non-deterministic), rather, it places a limit on the number of Blocks visited (deterministic).

The patch LGTM, but I'm curious, why do we end up with a bazillion edges, like what property do the blocks pointed at the edges have, like are they all going to an exit block, or in any case, is this a meaningful pattern - maybe we could avoid placement via the Hopfield Network, and instead do something simpler (and maybe it benefits the rest of the allocation)?



================
Comment at: llvm/lib/CodeGen/RegAllocGreedy.cpp:793
 
+  long Budget = GrowRegionComplexityBudget;
   while (true) {
----------------
You could just take `Visited` out of its conditional compilation block and compare it to `GrowRegionComplexityBudget`. I realize `Visited` is incremented less often than Budget is currently decremented, but it does achieve the same goal?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D120752/new/

https://reviews.llvm.org/D120752