[llvm] [TLI] ReplaceWithVecLib pass uses CostModel (PR #78688)

[Graham Hunter via llvm-commits]

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@@ -96,15 +102,55 @@ static void replaceWithTLIFunction(Instruction &I, VFInfo &Info,
     Replacement->copyFastMathFlags(&I);
 }
 
+/// Returns whether the vector library call \p TLIFunc costs more than the
+/// original instruction \p I.
+static bool isVeclibCallSlower(const TargetLibraryInfo &TLI,
+                               const TargetTransformInfo &TTI, Instruction &I,
+                               VectorType *VectorTy, CallInst *CI,
+                               Function *TLIFunc) {
+  SmallVector<Type *, 4> OpTypes;
+  for (auto &Op : CI ? CI->args() : I.operands())
+    OpTypes.push_back(Op->getType());
+
+  TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput;
+  InstructionCost DefaultCost;
+  if (CI) {
+    FastMathFlags FMF;
+    if (auto *FPMO = dyn_cast<FPMathOperator>(CI))
+      FMF = FPMO->getFastMathFlags();
+
+    SmallVector<const Value *> Args(CI->args());
+    IntrinsicCostAttributes CostAttrs(CI->getIntrinsicID(), VectorTy, Args,
+                                      OpTypes, FMF,
+                                      dyn_cast<IntrinsicInst>(CI));
+    DefaultCost = TTI.getIntrinsicInstrCost(CostAttrs, CostKind);
+  } else {
+    assert((I.getOpcode() == Instruction::FRem) && "Only FRem is supported");
+    auto Op2Info = TTI.getOperandInfo(I.getOperand(1));
+    SmallVector<const Value *, 4> OpValues(I.operand_values());
+    DefaultCost = TTI.getArithmeticInstrCost(
+        I.getOpcode(), VectorTy, CostKind,
+        {TargetTransformInfo::OK_AnyValue, TargetTransformInfo::OP_None},
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huntergr-arm wrote:

Are the arguments after CostKind actually needed? (They have defaults)

https://github.com/llvm/llvm-project/pull/78688