TargetSelect.cpp revision 8a8d479214745c82ef00f08d4e4f1c173b5f9ce2 
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 JIT to use, and allows
11// the user to specify a specific one on the commandline with -march=x. Clients
12// should initialize targets prior to calling createJIT.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/ExecutionEngine/ExecutionEngine.h"
17#include "llvm/Module.h"
18#include "llvm/ADT/Triple.h"
19#include "llvm/MC/SubtargetFeature.h"
20#include "llvm/Target/TargetMachine.h"
21#include "llvm/Support/CommandLine.h"
22#include "llvm/Support/Host.h"
23#include "llvm/Support/TargetRegistry.h"
24#include "llvm/Support/raw_ostream.h"
25using namespace llvm;
26
27/// selectTarget - Pick a target either via -march or by guessing the native
28/// arch.  Add any CPU features specified via -mcpu or -mattr.
29TargetMachine *EngineBuilder::selectTarget(Module *Mod,
30                              StringRef MArch,
31                              StringRef MCPU,
32                              const SmallVectorImpl<std::string>& MAttrs,
33                              Reloc::Model RM,
34                              CodeModel::Model CM,
35                              CodeGenOpt::Level OL,
36                              std::string *ErrorStr) {
37  Triple TheTriple(Mod->getTargetTriple());
38  if (TheTriple.getTriple().empty())
39    TheTriple.setTriple(sys::getDefaultTargetTriple());
40
41  // Adjust the triple to match what the user requested.
42  const Target *TheTarget = 0;
43  if (!MArch.empty()) {
44    for (TargetRegistry::iterator it = TargetRegistry::begin(),
45           ie = TargetRegistry::end(); it != ie; ++it) {
46      if (MArch == it->getName()) {
47        TheTarget = &*it;
48        break;
49      }
50    }
51
52    if (!TheTarget) {
53      *ErrorStr = "No available targets are compatible with this -march, "
54        "see -version for the available targets.\n";
55      return 0;
56    }
57
58    // Adjust the triple to match (if known), otherwise stick with the
59    // module/host triple.
60    Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
61    if (Type != Triple::UnknownArch)
62      TheTriple.setArch(Type);
63  } else {
64    std::string Error;
65    TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
66    if (TheTarget == 0) {
67      if (ErrorStr)
68        *ErrorStr = Error;
69      return 0;
70    }
71  }
72
73  if (!TheTarget->hasJIT()) {
74    errs() << "WARNING: This target JIT is not designed for the host you are"
75           << " running.  If bad things happen, please choose a different "
76           << "-march switch.\n";
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  // Allocate a target...
89  TargetOptions Options;
90  TargetMachine *Target = TheTarget->createTargetMachine(TheTriple.getTriple(),
91                                                         MCPU, FeaturesStr,
92                                                         Options,
93                                                         RM, CM, OL);
94  assert(Target && "Could not allocate target machine!");
95  return Target;
96}
97