[llvm] [LICM][WIP] Make an integer version of hoistFPAssociation. (PR #67736)

[Philip Reames via llvm-commits]

================
@@ -2719,6 +2728,65 @@ static bool hoistFPAssociation(Instruction &I, Loop &L,
   return true;
 }
 
+static bool hoistIntAssociation(Instruction &I, Loop &L,
+                                ICFLoopSafetyInfo &SafetyInfo,
+                                MemorySSAUpdater &MSSAU, AssumptionCache *AC,
+                                DominatorTree *DT) {
+  using namespace PatternMatch;
+  Value *VariantOp = nullptr, *InvariantOp = nullptr;
+
+  if (!match(&I, m_Mul(m_Value(VariantOp), m_Value(InvariantOp))))
+    return false;
+  if (L.isLoopInvariant(VariantOp))
+    std::swap(VariantOp, InvariantOp);
+  if (L.isLoopInvariant(VariantOp) || !L.isLoopInvariant(InvariantOp))
+    return false;
+  Value *Factor = InvariantOp;
+
+  // First, we need to make sure we should do the transformation.
+  SmallVector<Use *> Changes;
+  SmallVector<BinaryOperator *> Worklist;
+  if (BinaryOperator *VariantBinOp = dyn_cast<BinaryOperator>(VariantOp))
+    Worklist.push_back(VariantBinOp);
+  while (!Worklist.empty()) {
+    BinaryOperator *BO = Worklist.pop_back_val();
+    if (!BO->hasOneUse())
+      return false;
+    BinaryOperator *Op0, *Op1;
+    if (match(BO, m_Add(m_BinOp(Op0), m_BinOp(Op1)))) {
+      Worklist.push_back(Op0);
+      Worklist.push_back(Op1);
+      continue;
+    }
+    if (BO->getOpcode() != Instruction::Mul || L.isLoopInvariant(BO))
+      return false;
+    Use &U0 = BO->getOperandUse(0);
----------------
preames wrote:

In principle, we should match the entire mul reduce tree, and perform the transform if *any* of the operands are loop invariant.  Again, this is really a generalization on the prior code as well.  

https://github.com/llvm/llvm-project/pull/67736