[llvm] [VPlan] Don't apply predication discount to non-originally-predicated blocks (PR #160449)

[Florian Hahn via llvm-commits]

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@@ -855,7 +855,9 @@ InstructionCost VPRegionBlock::cost(ElementCount VF, VPCostContext &Ctx) {
   // For the scalar case, we may not always execute the original predicated
   // block, Thus, scale the block's cost by the probability of executing it.
   if (VF.isScalar())
-    return ThenCost / getPredBlockCostDivisor(Ctx.CostKind);
+    if (auto *VPIRBB = dyn_cast<VPIRBasicBlock>(Then))
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fhahn wrote:

The code here is dead, we don't compute the scalar cost in VPlan currently, as currently the VPlan for VF = 1 is not 100% accurate representation of the original scalar loop (e.g. could have multiple replicate regions for multiple original instructions in the same predicated block).

The code should be gone after a rebase

https://github.com/llvm/llvm-project/pull/160449