[llvm] [X86][CostModel] Estimate the codesize cost of switch (PR #163569)

[Nikita Popov via llvm-commits]

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@@ -6155,6 +6155,23 @@ X86TTIImpl::getIntImmCostIntrin(Intrinsic::ID IID, unsigned Idx,
 InstructionCost X86TTIImpl::getCFInstrCost(unsigned Opcode,
                                            TTI::TargetCostKind CostKind,
                                            const Instruction *I) const {
+  if (Opcode == Instruction::Switch && CostKind == TTI::TCK_CodeSize) {
+    unsigned JumpTableSize, NumSuccs = I->getNumSuccessors();
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nikic wrote:

Do we need to take into account whether the default is unreachable? onFinalizeSwitch() in InlineCost has some more complex logic for this.

https://github.com/llvm/llvm-project/pull/163569