[llvm] [VPlan] Compute cost for binary op VPInstruction with underlying values. (PR #125434)

[David Sherwood via llvm-commits]

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@@ -768,6 +768,27 @@ void VPInstruction::execute(VPTransformState &State) {
             /*IsScalar*/ GeneratesPerFirstLaneOnly);
 }
 
+InstructionCost VPInstruction::computeCost(ElementCount VF,
+                                           VPCostContext &Ctx) const {
+  if (Instruction::isBinaryOp(getOpcode())) {
+    if (!getUnderlyingValue())
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david-arm wrote:

Can you add a TODO here to deal with this case? Even if there isn't an underlying value, the cost of an add is still not zero. Alternatively, if there should always be an underlying value you could assert this?

https://github.com/llvm/llvm-project/pull/125434