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"
25 using 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.
29 TargetMachine *EngineBuilder::selectTarget(Module *Mod,
30                               StringRef MArch,
31                               StringRef MCPU,
32                               const SmallVectorImpl<std::string>& MAttrs,
33                               const TargetOptions &Options,
34                               Reloc::Model RM,
35                               CodeModel::Model CM,
36                               CodeGenOpt::Level OL,
37                               std::string *ErrorStr) {
38   Triple TheTriple(Mod->getTargetTriple());
39   if (TheTriple.getTriple().empty())
40     TheTriple.setTriple(sys::getDefaultTargetTriple());
41 
42   // Adjust the triple to match what the user requested.
43   const Target *TheTarget = 0;
44   if (!MArch.empty()) {
45     for (TargetRegistry::iterator it = TargetRegistry::begin(),
46            ie = TargetRegistry::end(); it != ie; ++it) {
47       if (MArch == it->getName()) {
48         TheTarget = &*it;
49         break;
50       }
51     }
52 
53     if (!TheTarget) {
54       *ErrorStr = "No available targets are compatible with this -march, "
55         "see -version for the available targets.\n";
56       return 0;
57     }
58 
59     // Adjust the triple to match (if known), otherwise stick with the
60     // module/host triple.
61     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
62     if (Type != Triple::UnknownArch)
63       TheTriple.setArch(Type);
64   } else {
65     std::string Error;
66     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
67     if (TheTarget == 0) {
68       if (ErrorStr)
69         *ErrorStr = Error;
70       return 0;
71     }
72   }
73 
74   if (!TheTarget->hasJIT()) {
75     errs() << "WARNING: This target JIT is not designed for the host you are"
76            << " running.  If bad things happen, please choose a different "
77            << "-march switch.\n";
78   }
79 
80   // Package up features to be passed to target/subtarget
81   std::string FeaturesStr;
82   if (!MAttrs.empty()) {
83     SubtargetFeatures Features;
84     for (unsigned i = 0; i != MAttrs.size(); ++i)
85       Features.AddFeature(MAttrs[i]);
86     FeaturesStr = Features.getString();
87   }
88 
89   // Allocate a target...
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