1//===- CostModel.cpp ------ Cost Model Analysis ---------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the cost model analysis. It provides a very basic cost
10// estimation for LLVM-IR. This analysis uses the services of the codegen
11// to approximate the cost of any IR instruction when lowered to machine
12// instructions. The cost results are unit-less and the cost number represents
13// the throughput of the machine assuming that all loads hit the cache, all
14// branches are predicted, etc. The cost numbers can be added in order to
15// compare two or more transformation alternatives.
16//
17//===----------------------------------------------------------------------===//
18
19#include "llvm/Analysis/CostModel.h"
20#include "llvm/Analysis/Passes.h"
21#include "llvm/Analysis/TargetTransformInfo.h"
22#include "llvm/IR/Function.h"
23#include "llvm/IR/PassManager.h"
24#include "llvm/InitializePasses.h"
25#include "llvm/Pass.h"
26#include "llvm/Support/CommandLine.h"
27#include "llvm/Support/raw_ostream.h"
28#include "llvm/IR/IntrinsicInst.h"
29using namespace llvm;
30
31static cl::opt<TargetTransformInfo::TargetCostKind> CostKind(
32 "cost-kind", cl::desc("Target cost kind"),
33 cl::init(Val: TargetTransformInfo::TCK_RecipThroughput),
34 cl::values(clEnumValN(TargetTransformInfo::TCK_RecipThroughput,
35 "throughput", "Reciprocal throughput"),
36 clEnumValN(TargetTransformInfo::TCK_Latency,
37 "latency", "Instruction latency"),
38 clEnumValN(TargetTransformInfo::TCK_CodeSize,
39 "code-size", "Code size"),
40 clEnumValN(TargetTransformInfo::TCK_SizeAndLatency,
41 "size-latency", "Code size and latency")));
42
43static cl::opt<bool> TypeBasedIntrinsicCost("type-based-intrinsic-cost",
44 cl::desc("Calculate intrinsics cost based only on argument types"),
45 cl::init(Val: false));
46
47#define CM_NAME "cost-model"
48#define DEBUG_TYPE CM_NAME
49
50PreservedAnalyses CostModelPrinterPass::run(Function &F,
51 FunctionAnalysisManager &AM) {
52 auto &TTI = AM.getResult<TargetIRAnalysis>(IR&: F);
53 OS << "Printing analysis 'Cost Model Analysis' for function '" << F.getName() << "':\n";
54 for (BasicBlock &B : F) {
55 for (Instruction &Inst : B) {
56 // TODO: Use a pass parameter instead of cl::opt CostKind to determine
57 // which cost kind to print.
58 InstructionCost Cost;
59 auto *II = dyn_cast<IntrinsicInst>(Val: &Inst);
60 if (II && TypeBasedIntrinsicCost) {
61 IntrinsicCostAttributes ICA(II->getIntrinsicID(), *II,
62 InstructionCost::getInvalid(), true);
63 Cost = TTI.getIntrinsicInstrCost(ICA, CostKind);
64 }
65 else {
66 Cost = TTI.getInstructionCost(U: &Inst, CostKind);
67 }
68
69 if (auto CostVal = Cost.getValue())
70 OS << "Cost Model: Found an estimated cost of " << *CostVal;
71 else
72 OS << "Cost Model: Invalid cost";
73
74 OS << " for instruction: " << Inst << "\n";
75 }
76 }
77 return PreservedAnalyses::all();
78}
79