[llvm] [VPlan] Model cost of safe-divisor in VPlan (PR #154468)

[David Sherwood via llvm-commits]

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@@ -7949,6 +7949,7 @@ VPWidenRecipe *VPRecipeBuilder::tryToWiden(Instruction *I,
       VPValue *One =
           Plan.getOrAddLiveIn(ConstantInt::get(I->getType(), 1u, false));
       auto *SafeRHS = Builder.createSelect(Mask, Ops[1], One, I->getDebugLoc());
+      SafeRHS->setUnderlyingValue(I);
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david-arm wrote:

Will this confuse `VPSlotTracker::assignName`, since there will be two VPValues with the same underlying value? I guess it also means that the select would be ignored along with the div in both `calculateRegisterUsageForPlan` and `VPRecipeBase::cost`, which perhaps isn't a bad thing?

https://github.com/llvm/llvm-project/pull/154468