[llvm] [llvm][LICM] Add flag to control re-association (PR #149829)

[Theodoros Theodoridis via llvm-commits]

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@@ -2850,7 +2855,7 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
   bool LVInRHS = L.isLoopInvariant(BO->getOperand(0));
   auto *BO0 = dyn_cast<BinaryOperator>(BO->getOperand(LVInRHS));
   if (!BO0 || BO0->getOpcode() != Opcode || !BO0->isAssociative() ||
-      BO0->hasNUsesOrMore(3))
+      BO0->hasNUsesOrMore(BOAssociationUserLimit + 1))
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thetheodor wrote:

Regarding the motivation: we (at NVIDIA) have found that in some cases too much re-association can lead to higher register pressure, especially when there are multiple uses inside a loop. We'd like a way to control this behavior.

https://github.com/llvm/llvm-project/pull/149829