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This is not just a matter of passing in the target triple from the module; currently backends are making decisions based on the build and host architecture. The goal is to migrate to making these decisions based off of the triple (in conjunction with the feature string). Thus most clients pass in the target triple, or the host triple if that is empty. This has one important change in the way behavior of the JIT and llc. For the JIT, it was previously selecting the Target based on the host (naturally), but it was setting the target machine features based on the triple from the module. Now it is setting the target machine features based on the triple of the host. For LLC, -march was previously only used to select the target, the target machine features were initialized from the module's triple (which may have been empty). Now the target triple is taken from the module, or the host's triple is used if that is empty. Then the triple is adjusted to match -march. The take away is that -march for llc is now used in conjunction with the host triple to initialize the subtarget. If users want more deterministic behavior from llc, they should use -mtriple, or set the triple in the input module. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77946 91177308-0d34-0410-b5e6-96231b3b80d8
87 lines
2.9 KiB
C++
87 lines
2.9 KiB
C++
//===-- TargetSelect.cpp - Target Chooser Code ----------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This just asks the TargetRegistry for the appropriate JIT to use, and allows
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// the user to specify a specific one on the commandline with -march=x. Clients
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// should initialize targets prior to calling createJIT.
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//
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//===----------------------------------------------------------------------===//
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#include "JIT.h"
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#include "llvm/Module.h"
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#include "llvm/ModuleProvider.h"
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#include "llvm/ADT/Triple.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/System/Host.h"
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#include "llvm/Target/SubtargetFeature.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegistry.h"
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using namespace llvm;
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static cl::opt<std::string>
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MArch("march", cl::desc("Architecture to generate assembly for (see --version)"));
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static cl::opt<std::string>
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MCPU("mcpu",
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cl::desc("Target a specific cpu type (-mcpu=help for details)"),
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cl::value_desc("cpu-name"),
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cl::init(""));
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static cl::list<std::string>
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MAttrs("mattr",
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cl::CommaSeparated,
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cl::desc("Target specific attributes (-mattr=help for details)"),
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cl::value_desc("a1,+a2,-a3,..."));
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/// selectTarget - Pick a target either via -march or by guessing the native
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/// arch. Add any CPU features specified via -mcpu or -mattr.
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TargetMachine *JIT::selectTarget(ModuleProvider *MP, std::string *ErrorStr) {
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Triple TheTriple(sys::getHostTriple());
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// Adjust the triple to match what the user requested.
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if (!MArch.empty())
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TheTriple.setArch(Triple::getArchTypeForLLVMName(MArch));
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std::string Error;
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const Target *TheTarget =
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TargetRegistry::lookupTarget(TheTriple.getTriple(),
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/*FallbackToHost=*/false,
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/*RequireJIT=*/false,
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Error);
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if (TheTarget == 0) {
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if (ErrorStr)
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*ErrorStr = Error;
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return 0;
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}
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if (!TheTarget->hasJIT()) {
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errs() << "WARNING: This target JIT is not designed for the host you are"
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<< " running. If bad things happen, please choose a different "
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<< "-march switch.\n";
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}
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// Package up features to be passed to target/subtarget
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std::string FeaturesStr;
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if (!MCPU.empty() || !MAttrs.empty()) {
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SubtargetFeatures Features;
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Features.setCPU(MCPU);
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for (unsigned i = 0; i != MAttrs.size(); ++i)
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Features.AddFeature(MAttrs[i]);
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FeaturesStr = Features.getString();
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}
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// Allocate a target...
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TargetMachine *Target =
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TheTarget->createTargetMachine(*MP->getModule(), TheTriple.getTriple(),
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FeaturesStr);
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assert(Target && "Could not allocate target machine!");
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return Target;
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}
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