xref: /freebsd/contrib/llvm-project/llvm/lib/Analysis/CostModel.cpp (revision 5f757f3ff9144b609b3c433dfd370cc6bdc191ad)
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"
29 using namespace llvm;
30 
31 static cl::opt<TargetTransformInfo::TargetCostKind> CostKind(
32     "cost-kind", cl::desc("Target cost kind"),
33     cl::init(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 
43 static cl::opt<bool> TypeBasedIntrinsicCost("type-based-intrinsic-cost",
44     cl::desc("Calculate intrinsics cost based only on argument types"),
45     cl::init(false));
46 
47 #define CM_NAME "cost-model"
48 #define DEBUG_TYPE CM_NAME
49 
50 PreservedAnalyses CostModelPrinterPass::run(Function &F,
51                                             FunctionAnalysisManager &AM) {
52   auto &TTI = AM.getResult<TargetIRAnalysis>(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>(&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(&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