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      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       *ErrorStr = "No available targets are compatible with this -march, "
     60         "see -version for the available targets.\n";
     61       return 0;
     62     }
     63 
     64     // Adjust the triple to match (if known), otherwise stick with the
     65     // requested/host triple.
     66     Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
     67     if (Type != Triple::UnknownArch)
     68       TheTriple.setArch(Type);
     69   } else {
     70     std::string Error;
     71     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), Error);
     72     if (TheTarget == 0) {
     73       if (ErrorStr)
     74         *ErrorStr = Error;
     75       return 0;
     76     }
     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   TargetMachine *Target = TheTarget->createTargetMachine(TheTriple.getTriple(),
     90                                                          MCPU, FeaturesStr,
     91                                                          Options,
     92                                                          RelocModel, CMModel,
     93                                                          OptLevel);
     94   assert(Target && "Could not allocate target machine!");
     95   return Target;
     96 }
     97