1//===-- TargetSelect.cpp - Target Chooser Code ----------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This just asks the TargetRegistry for the appropriate target to use, and
11// allows the user to specify a specific one on the commandline with -march=x,
12// -mcpu=y, and -mattr=a,-b,+c. Clients should initialize targets prior to
13// calling selectTarget().
14//
15//===----------------------------------------------------------------------===//
16
17#include "llvm/ExecutionEngine/ExecutionEngine.h"
18#include "llvm/ADT/Triple.h"
19#include "llvm/IR/Module.h"
20#include "llvm/MC/SubtargetFeature.h"
21#include "llvm/Support/CommandLine.h"
22#include "llvm/Support/Host.h"
23#include "llvm/Support/TargetRegistry.h"
24#include "llvm/Target/TargetMachine.h"
25
26using namespace llvm;
27
28TargetMachine *EngineBuilder::selectTarget() {
29  Triple TT;
30
31  // MCJIT can generate code for remote targets, but the old JIT and Interpreter
32  // must use the host architecture.
33  if (UseMCJIT && WhichEngine != EngineKind::Interpreter && M)
34    TT.setTriple(M->getTargetTriple());
35
36  return selectTarget(TT, MArch, MCPU, MAttrs);
37}
38
39/// selectTarget - Pick a target either via -march or by guessing the native
40/// arch.  Add any CPU features specified via -mcpu or -mattr.
41TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
42                              StringRef MArch,
43                              StringRef MCPU,
44                              const SmallVectorImpl<std::string>& MAttrs) {
45  Triple TheTriple(TargetTriple);
46  if (TheTriple.getTriple().empty())
47    TheTriple.setTriple(sys::getProcessTriple());
48
49  // Adjust the triple to match what the user requested.
50  const Target *TheTarget = nullptr;
51  if (!MArch.empty()) {
52    for (TargetRegistry::iterator it = TargetRegistry::begin(),
53           ie = TargetRegistry::end(); it != ie; ++it) {
54      if (MArch == it->getName()) {
55        TheTarget = &*it;
56        break;
57      }
58    }
59
60    if (!TheTarget) {
61      if (ErrorStr)
62        *ErrorStr = "No available targets are compatible with this -march, "
63                    "see -version for the available targets.\n";
64      return nullptr;
65    }
66
67    // Adjust the triple to match (if known), otherwise stick with the
68    // requested/host triple.
69    Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
70    if (Type != Triple::UnknownArch)
71      TheTriple.setArch(Type);
72  } else {
73    std::string Error;
74    TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
75    if (!TheTarget) {
76      if (ErrorStr)
77        *ErrorStr = Error;
78      return nullptr;
79    }
80  }
81
82  // Package up features to be passed to target/subtarget
83  std::string FeaturesStr;
84  if (!MAttrs.empty()) {
85    SubtargetFeatures Features;
86    for (unsigned i = 0; i != MAttrs.size(); ++i)
87      Features.AddFeature(MAttrs[i]);
88    FeaturesStr = Features.getString();
89  }
90
91  // FIXME: non-iOS ARM FastISel is broken with MCJIT.
92  if (UseMCJIT &&
93      TheTriple.getArch() == Triple::arm &&
94      !TheTriple.isiOS() &&
95      OptLevel == CodeGenOpt::None) {
96    OptLevel = CodeGenOpt::Less;
97  }
98
99  // Allocate a target...
100  TargetMachine *Target = TheTarget->createTargetMachine(TheTriple.getTriple(),
101                                                         MCPU, FeaturesStr,
102                                                         Options,
103                                                         RelocModel, CMModel,
104                                                         OptLevel);
105  assert(Target && "Could not allocate target machine!");
106  return Target;
107}
108