Break infinite loop when the Hopfield network oscillates.
This is impossible in theory, I can prove it. In practice, our near-zero
threshold can cause the network to oscillate between equally good
solutions.
<rdar://problem/9720596>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134428 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index 195e483..3434a92 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -649,8 +649,6 @@
for (;;) {
ArrayRef<unsigned> NewBundles = SpillPlacer->getRecentPositive();
- if (NewBundles.empty())
- break;
// Find new through blocks in the periphery of PrefRegBundles.
for (int i = 0, e = NewBundles.size(); i != e; ++i) {
unsigned Bundle = NewBundles[i];
@@ -670,12 +668,12 @@
}
}
// Any new blocks to add?
- if (ActiveBlocks.size() > AddedTo) {
- ArrayRef<unsigned> Add(&ActiveBlocks[AddedTo],
- ActiveBlocks.size() - AddedTo);
- addThroughConstraints(Intf, Add);
- AddedTo = ActiveBlocks.size();
- }
+ if (ActiveBlocks.size() == AddedTo)
+ break;
+ addThroughConstraints(Intf,
+ ArrayRef<unsigned>(ActiveBlocks).slice(AddedTo));
+ AddedTo = ActiveBlocks.size();
+
// Perhaps iterating can enable more bundles?
SpillPlacer->iterate();
}