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/ADT/Triple.h"
18#include "llvm/ExecutionEngine/ExecutionEngine.h"
19#include "llvm/IR/Module.h"
20#include "llvm/MC/SubtargetFeature.h"
21#include "llvm/Support/Host.h"
22#include "llvm/Support/TargetRegistry.h"
23#include "llvm/Target/TargetMachine.h"
24
25using namespace llvm;
26
27TargetMachine *EngineBuilder::selectTarget() {
28  Triple TT;
29
30  // MCJIT can generate code for remote targets, but the old JIT and Interpreter
31  // must use the host architecture.
32  if (WhichEngine != EngineKind::Interpreter && M)
33    TT.setTriple(M->getTargetTriple());
34
35  return selectTarget(TT, MArch, MCPU, MAttrs);
36}
37
38/// selectTarget - Pick a target either via -march or by guessing the native
39/// arch.  Add any CPU features specified via -mcpu or -mattr.
40TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
41                              StringRef MArch,
42                              StringRef MCPU,
43                              const SmallVectorImpl<std::string>& MAttrs) {
44  Triple TheTriple(TargetTriple);
45  if (TheTriple.getTriple().empty())
46    TheTriple.setTriple(sys::getProcessTriple());
47
48  // Adjust the triple to match what the user requested.
49  const Target *TheTarget = nullptr;
50  if (!MArch.empty()) {
51    auto I = std::find_if(
52        TargetRegistry::targets().begin(), TargetRegistry::targets().end(),
53        [&](const Target &T) { return MArch == T.getName(); });
54
55    if (I == TargetRegistry::targets().end()) {
56      if (ErrorStr)
57        *ErrorStr = "No available targets are compatible with this -march, "
58                    "see -version for the available targets.\n";
59      return nullptr;
60    }
61
62    TheTarget = &*I;
63
64    // Adjust the triple to match (if known), otherwise stick with the
65    // requested/host triple.
66    Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
67    if (Type != Triple::UnknownArch)
68      TheTriple.setArch(Type);
69  } else {
70    std::string Error;
71    TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
72    if (!TheTarget) {
73      if (ErrorStr)
74        *ErrorStr = Error;
75      return nullptr;
76    }
77  }
78
79  // Package up features to be passed to target/subtarget
80  std::string FeaturesStr;
81  if (!MAttrs.empty()) {
82    SubtargetFeatures Features;
83    for (unsigned i = 0; i != MAttrs.size(); ++i)
84      Features.AddFeature(MAttrs[i]);
85    FeaturesStr = Features.getString();
86  }
87
88  // FIXME: non-iOS ARM FastISel is broken with MCJIT.
89  if (TheTriple.getArch() == Triple::arm &&
90      !TheTriple.isiOS() &&
91      OptLevel == CodeGenOpt::None) {
92    OptLevel = CodeGenOpt::Less;
93  }
94
95  // Allocate a target...
96  TargetMachine *Target = TheTarget->createTargetMachine(TheTriple.getTriple(),
97                                                         MCPU, FeaturesStr,
98                                                         Options,
99                                                         RelocModel, CMModel,
100                                                         OptLevel);
101  assert(Target && "Could not allocate target machine!");
102  return Target;
103}
104