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/ExecutionEngine/ExecutionEngine.h"
18 #include "llvm/Module.h"
19 #include "llvm/ADT/Triple.h"
20 #include "llvm/MC/SubtargetFeature.h"
21 #include "llvm/Target/TargetMachine.h"
22 #include "llvm/Support/CommandLine.h"
23 #include "llvm/Support/Host.h"
24 #include "llvm/Support/TargetRegistry.h"
25 
26 using namespace llvm;
27 
28 TargetMachine *EngineBuilder::selectTarget() {
29   StringRef MArch = "";
30   StringRef MCPU = "";
31   SmallVector<std::string, 1> MAttrs;
32   Triple TT(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.
39 TargetMachine *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::getDefaultTargetTriple());
46 
47   // Adjust the triple to match what the user requested.
48   const Target *TheTarget = 0;
49   if (!MArch.empty()) {
50     for (TargetRegistry::iterator it = TargetRegistry::begin(),
51            ie = TargetRegistry::end(); it != ie; ++it) {
52       if (MArch == it->getName()) {
53         TheTarget = &*it;
54         break;
55       }
56     }
57 
58     if (!TheTarget) {
59       if (ErrorStr)
60         *ErrorStr = "No available targets are compatible with this -march, "
61                     "see -version for the available targets.\n";
62       return 0;
63     }
64 
65     // Adjust the triple to match (if known), otherwise stick with the
66     // requested/host triple.
67     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
68     if (Type != Triple::UnknownArch)
69       TheTriple.setArch(Type);
70   } else {
71     std::string Error;
72     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
73     if (TheTarget == 0) {
74       if (ErrorStr)
75         *ErrorStr = Error;
76       return 0;
77     }
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                                                          RelocModel, CMModel,
94                                                          OptLevel);
95   assert(Target && "Could not allocate target machine!");
96   return Target;
97 }
98