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   Triple TT;
30 
31   // MCJIT can generate code for remote targets, but the old JIT and Interpreter
32   // must use the host architecture.
33   if (UseMCJIT && WhichEngine != EngineKind::Interpreter && M)
34     TT.setTriple(M->getTargetTriple());
35   else
36     TT.setTriple(LLVM_HOSTTRIPLE);
37   return selectTarget(TT, MArch, MCPU, MAttrs);
38 }
39 
40 /// selectTarget - Pick a target either via -march or by guessing the native
41 /// arch.  Add any CPU features specified via -mcpu or -mattr.
42 TargetMachine *EngineBuilder::selectTarget(const Triple &TargetTriple,
43                               StringRef MArch,
44                               StringRef MCPU,
45                               const SmallVectorImpl<std::string>& MAttrs) {
46   Triple TheTriple(TargetTriple);
47   if (TheTriple.getTriple().empty())
48     TheTriple.setTriple(sys::getDefaultTargetTriple());
49 
50   // Adjust the triple to match what the user requested.
51   const Target *TheTarget = 0;
52   if (!MArch.empty()) {
53     for (TargetRegistry::iterator it = TargetRegistry::begin(),
54            ie = TargetRegistry::end(); it != ie; ++it) {
55       if (MArch == it->getName()) {
56         TheTarget = &*it;
57         break;
58       }
59     }
60 
61     if (!TheTarget) {
62       if (ErrorStr)
63         *ErrorStr = "No available targets are compatible with this -march, "
64                     "see -version for the available targets.\n";
65       return 0;
66     }
67 
68     // Adjust the triple to match (if known), otherwise stick with the
69     // requested/host triple.
70     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
71     if (Type != Triple::UnknownArch)
72       TheTriple.setArch(Type);
73   } else {
74     std::string Error;
75     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
76     if (TheTarget == 0) {
77       if (ErrorStr)
78         *ErrorStr = Error;
79       return 0;
80     }
81   }
82 
83   // Package up features to be passed to target/subtarget
84   std::string FeaturesStr;
85   if (!MAttrs.empty()) {
86     SubtargetFeatures Features;
87     for (unsigned i = 0; i != MAttrs.size(); ++i)
88       Features.AddFeature(MAttrs[i]);
89     FeaturesStr = Features.getString();
90   }
91 
92   // Allocate a target...
93   TargetMachine *Target = TheTarget->createTargetMachine(TheTriple.getTriple(),
94                                                          MCPU, FeaturesStr,
95                                                          Options,
96                                                          RelocModel, CMModel,
97                                                          OptLevel);
98   assert(Target && "Could not allocate target machine!");
99   return Target;
100 }
101