TargetSelect.cpp revision 223013 
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/Support/CommandLine.h"
20#include "llvm/Support/raw_ostream.h"
21#include "llvm/Support/Host.h"
22#include "llvm/Target/SubtargetFeature.h"
23#include "llvm/Target/TargetMachine.h"
24#include "llvm/Target/TargetRegistry.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                              std::string *ErrorStr) {
34  Triple TheTriple(Mod->getTargetTriple());
35  if (TheTriple.getTriple().empty())
36    TheTriple.setTriple(sys::getHostTriple());
37
38  // Adjust the triple to match what the user requested.
39  const Target *TheTarget = 0;
40  if (!MArch.empty()) {
41    for (TargetRegistry::iterator it = TargetRegistry::begin(),
42           ie = TargetRegistry::end(); it != ie; ++it) {
43      if (MArch == it->getName()) {
44        TheTarget = &*it;
45        break;
46      }
47    }
48
49    if (!TheTarget) {
50      *ErrorStr = "No available targets are compatible with this -march, "
51        "see -version for the available targets.\n";
52      return 0;
53    }
54
55    // Adjust the triple to match (if known), otherwise stick with the
56    // module/host triple.
57    Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
58    if (Type != Triple::UnknownArch)
59      TheTriple.setArch(Type);
60  } else {
61    std::string Error;
62    TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
63    if (TheTarget == 0) {
64      if (ErrorStr)
65        *ErrorStr = Error;
66      return 0;
67    }
68  }
69
70  if (!TheTarget->hasJIT()) {
71    errs() << "WARNING: This target JIT is not designed for the host you are"
72           << " running.  If bad things happen, please choose a different "
73           << "-march switch.\n";
74  }
75
76  // Package up features to be passed to target/subtarget
77  std::string FeaturesStr;
78  if (!MCPU.empty() || !MAttrs.empty()) {
79    SubtargetFeatures Features;
80    Features.setCPU(MCPU);
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(), FeaturesStr);
89  assert(Target && "Could not allocate target machine!");
90  return Target;
91}
92