1//===-- TargetSelect.cpp - Target Chooser Code ----------------------------===//
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 just asks the TargetRegistry for the appropriate target to use, and
10// allows the user to specify a specific one on the commandline with -march=x,
11// -mcpu=y, and -mattr=a,-b,+c. Clients should initialize targets prior to
12// calling selectTarget().
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/ADT/Triple.h"
17#include "llvm/ExecutionEngine/ExecutionEngine.h"
18#include "llvm/IR/Module.h"
19#include "llvm/MC/SubtargetFeature.h"
20#include "llvm/Support/Host.h"
21#include "llvm/Support/TargetRegistry.h"
22#include "llvm/Target/TargetMachine.h"
23
24using namespace llvm;
25
26TargetMachine *EngineBuilder::selectTarget() {
27  Triple TT;
28
29  // MCJIT can generate code for remote targets, but the old JIT and Interpreter
30  // must use the host architecture.
31  if (WhichEngine != EngineKind::Interpreter && M)
32    TT.setTriple(M->getTargetTriple());
33
34  return selectTarget(TT, MArch, MCPU, MAttrs);
35}
36
37/// selectTarget - Pick a target either via -march or by guessing the native
38/// arch.  Add any CPU features specified via -mcpu or -mattr.
39TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
40                              StringRef MArch,
41                              StringRef MCPU,
42                              const SmallVectorImpl<std::string>& MAttrs) {
43  Triple TheTriple(TargetTriple);
44  if (TheTriple.getTriple().empty())
45    TheTriple.setTriple(sys::getProcessTriple());
46
47  // Adjust the triple to match what the user requested.
48  const Target *TheTarget = nullptr;
49  if (!MArch.empty()) {
50    auto I = find_if(TargetRegistry::targets(),
51                     [&](const Target &T) { return MArch == T.getName(); });
52
53    if (I == TargetRegistry::targets().end()) {
54      if (ErrorStr)
55        *ErrorStr = "No available targets are compatible with this -march, "
56                    "see -version for the available targets.\n";
57      return nullptr;
58    }
59
60    TheTarget = &*I;
61
62    // Adjust the triple to match (if known), otherwise stick with the
63    // requested/host triple.
64    Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
65    if (Type != Triple::UnknownArch)
66      TheTriple.setArch(Type);
67  } else {
68    std::string Error;
69    TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
70    if (!TheTarget) {
71      if (ErrorStr)
72        *ErrorStr = Error;
73      return nullptr;
74    }
75  }
76
77  // Package up features to be passed to target/subtarget
78  std::string FeaturesStr;
79  if (!MAttrs.empty()) {
80    SubtargetFeatures Features;
81    for (unsigned i = 0; i != MAttrs.size(); ++i)
82      Features.AddFeature(MAttrs[i]);
83    FeaturesStr = Features.getString();
84  }
85
86  // Allocate a target...
87  TargetMachine *Target =
88      TheTarget->createTargetMachine(TheTriple.getTriple(), MCPU, FeaturesStr,
89                                     Options, RelocModel, CMModel, OptLevel,
90				     /*JIT*/ true);
91  Target->Options.EmulatedTLS = EmulatedTLS;
92  Target->Options.ExplicitEmulatedTLS = true;
93
94  assert(Target && "Could not allocate target machine!");
95  return Target;
96}
97