[llvm] [VPlan] Simplify live-ins early using SCEV. (PR #155304)

[Florian Hahn via llvm-commits]

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@@ -7969,32 +7969,8 @@ VPWidenRecipe *VPRecipeBuilder::tryToWiden(Instruction *I,
   case Instruction::Shl:
   case Instruction::Sub:
   case Instruction::Xor:
-  case Instruction::Freeze: {
-    SmallVector<VPValue *> NewOps(Operands);
-    if (Instruction::isBinaryOp(I->getOpcode())) {
-      // The legacy cost model uses SCEV to check if some of the operands are
-      // constants. To match the legacy cost model's behavior, use SCEV to try
-      // to replace operands with constants.
-      ScalarEvolution &SE = *PSE.getSE();
-      auto GetConstantViaSCEV = [this, &SE](VPValue *Op) {
-        if (!Op->isLiveIn())
-          return Op;
-        Value *V = Op->getUnderlyingValue();
-        if (isa<Constant>(V) || !SE.isSCEVable(V->getType()))
-          return Op;
-        auto *C = dyn_cast<SCEVConstant>(SE.getSCEV(V));
-        if (!C)
-          return Op;
-        return Plan.getOrAddLiveIn(C->getValue());
-      };
-      // For Mul, the legacy cost model checks both operands.
-      if (I->getOpcode() == Instruction::Mul)
-        NewOps[0] = GetConstantViaSCEV(NewOps[0]);
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fhahn wrote:

I couldn't find any in my testing

https://github.com/llvm/llvm-project/pull/155304