[PATCH] D130651: RegAllocGreedy: Fix nondeterminism in tryLastChanceRecoloring

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
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tryLastChanceRecoloring iterates over the set of LiveInterval pointers
and used that to seed the recoloring stack, which was
nondeterministic. Fixes a future test failing about 20% of the time.

      

This just takes the order the interfering vreg was encountered. Not
sure if we should try to order this more intelligently.


https://reviews.llvm.org/D130651

Files:
  llvm/lib/CodeGen/RegAllocGreedy.h


Index: llvm/lib/CodeGen/RegAllocGreedy.h
===================================================================
--- llvm/lib/CodeGen/RegAllocGreedy.h
+++ llvm/lib/CodeGen/RegAllocGreedy.h
@@ -150,7 +150,7 @@
 private:
   // Convenient shortcuts.
   using PQueue = std::priority_queue<std::pair<unsigned, unsigned>>;
-  using SmallLISet = SmallPtrSet<const LiveInterval *, 4>;
+  using SmallLISet = SmallSetVector<const LiveInterval *, 4>;
 
   // We need to track all tentative recolorings so we can roll back any
   // successful and unsuccessful recoloring attempts.


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