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+//===- CostModel.cpp ------ Cost Model Analysis ---------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the cost model analysis. It provides a very basic cost
+// estimation for LLVM-IR. This analysis uses the services of the codegen
+// to approximate the cost of any IR instruction when lowered to machine
+// instructions. The cost results are unit-less and the cost number represents
+// the throughput of the machine assuming that all loads hit the cache, all
+// branches are predicted, etc. The cost numbers can be added in order to
+// compare two or more transformation alternatives.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+static cl::opt<TargetTransformInfo::TargetCostKind> CostKind(
+ "cost-kind", cl::desc("Target cost kind"),
+ cl::init(TargetTransformInfo::TCK_RecipThroughput),
+ cl::values(clEnumValN(TargetTransformInfo::TCK_RecipThroughput,
+ "throughput", "Reciprocal throughput"),
+ clEnumValN(TargetTransformInfo::TCK_Latency,
+ "latency", "Instruction latency"),
+ clEnumValN(TargetTransformInfo::TCK_CodeSize,
+ "code-size", "Code size")));
+
+#define CM_NAME "cost-model"
+#define DEBUG_TYPE CM_NAME
+
+namespace {
+ class CostModelAnalysis : public FunctionPass {
+
+ public:
+ static char ID; // Class identification, replacement for typeinfo
+ CostModelAnalysis() : FunctionPass(ID), F(nullptr), TTI(nullptr) {
+ initializeCostModelAnalysisPass(
+ *PassRegistry::getPassRegistry());
+ }
+
+ /// Returns the expected cost of the instruction.
+ /// Returns -1 if the cost is unknown.
+ /// Note, this method does not cache the cost calculation and it
+ /// can be expensive in some cases.
+ unsigned getInstructionCost(const Instruction *I) const {
+ return TTI->getInstructionCost(I, TargetTransformInfo::TCK_RecipThroughput);
+ }
+
+ private:
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+ bool runOnFunction(Function &F) override;
+ void print(raw_ostream &OS, const Module*) const override;
+
+ /// The function that we analyze.
+ Function *F;
+ /// Target information.
+ const TargetTransformInfo *TTI;
+ };
+} // End of anonymous namespace
+
+// Register this pass.
+char CostModelAnalysis::ID = 0;
+static const char cm_name[] = "Cost Model Analysis";
+INITIALIZE_PASS_BEGIN(CostModelAnalysis, CM_NAME, cm_name, false, true)
+INITIALIZE_PASS_END (CostModelAnalysis, CM_NAME, cm_name, false, true)
+
+FunctionPass *llvm::createCostModelAnalysisPass() {
+ return new CostModelAnalysis();
+}
+
+void
+CostModelAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+}
+
+bool
+CostModelAnalysis::runOnFunction(Function &F) {
+ this->F = &F;
+ auto *TTIWP = getAnalysisIfAvailable<TargetTransformInfoWrapperPass>();
+ TTI = TTIWP ? &TTIWP->getTTI(F) : nullptr;
+
+ return false;
+}
+
+void CostModelAnalysis::print(raw_ostream &OS, const Module*) const {
+ if (!F)
+ return;
+
+ for (BasicBlock &B : *F) {
+ for (Instruction &Inst : B) {
+ unsigned Cost = TTI->getInstructionCost(&Inst, CostKind);
+ if (Cost != (unsigned)-1)
+ OS << "Cost Model: Found an estimated cost of " << Cost;
+ else
+ OS << "Cost Model: Unknown cost";
+
+ OS << " for instruction: " << Inst << "\n";
+ }
+ }
+}