(pascal   03-Sep-16) 

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: //===-- TargetMachine.cpp - General Target Information ---------------------==//

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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 file describes the general parts of a Target machine.

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: //

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: //===----------------------------------------------------------------------===//

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: 

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: #include "llvm/Target/TargetMachine.h"

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: #include "llvm/Analysis/TargetTransformInfo.h"

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: #include "llvm/IR/Function.h"

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: #include "llvm/IR/GlobalAlias.h"

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: #include "llvm/IR/GlobalValue.h"

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: #include "llvm/IR/GlobalVariable.h"

 (patrick  14-Jan-17) 

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: #include "llvm/IR/LegacyPassManager.h"

 (pascal   03-Sep-16) 

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: #include "llvm/IR/Mangler.h"

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: #include "llvm/MC/MCAsmInfo.h"

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: #include "llvm/MC/MCContext.h"

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: #include "llvm/MC/MCInstrInfo.h"

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: #include "llvm/MC/MCSectionMachO.h"

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: #include "llvm/MC/MCTargetOptions.h"

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: #include "llvm/MC/SectionKind.h"

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: #include "llvm/Target/TargetLoweringObjectFile.h"

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: using namespace llvm;

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: 

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: //---------------------------------------------------------------------------

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: // TargetMachine Class

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: //

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: 

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: TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,

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:                              const Triple &TT, StringRef CPU, StringRef FS,

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:                              const TargetOptions &Options)

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:     : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),

 (patrick  14-Jan-17) 

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:       TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),

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:       RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {

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: }

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: 

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: TargetMachine::~TargetMachine() = default;

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: 

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: bool TargetMachine::isPositionIndependent() const {

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:   return getRelocationModel() == Reloc::PIC_;

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: }

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: 

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: /// Reset the target options based on the function's attributes.

 (pascal   03-Sep-16) 

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: // FIXME: This function needs to go away for a number of reasons:

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: // a) global state on the TargetMachine is terrible in general,

 (patrick  24-Jan-17) 

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: // b) these target options should be passed only on the function

 (pascal   03-Sep-16) 

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: //    and not on the TargetMachine (via TargetOptions) at all.

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: void TargetMachine::resetTargetOptions(const Function &F) const {

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: #define RESET_OPTION(X, Y)                                                     \

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:   do {                                                                         \

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:     if (F.hasFnAttribute(Y))                                                   \

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:       Options.X = (F.getFnAttribute(Y).getValueAsString() == "true");          \

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:     else                                                                       \

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:       Options.X = DefaultOptions.X;                                            \

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:   } while (0)

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: 

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:   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");

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:   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");

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:   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");

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:   RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");

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:   RESET_OPTION(NoTrappingFPMath, "no-trapping-math");

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: 

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:   StringRef Denormal =

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:     F.getFnAttribute("denormal-fp-math").getValueAsString();

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:   if (Denormal == "ieee")

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:     Options.FPDenormalMode = FPDenormal::IEEE;

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:   else if (Denormal == "preserve-sign")

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:     Options.FPDenormalMode = FPDenormal::PreserveSign;

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:   else if (Denormal == "positive-zero")

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:     Options.FPDenormalMode = FPDenormal::PositiveZero;

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:   else

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:     Options.FPDenormalMode = DefaultOptions.FPDenormalMode;

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: }

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: 

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: /// Returns the code generation relocation model. The choices are static, PIC,

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: /// and dynamic-no-pic.

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: Reloc::Model TargetMachine::getRelocationModel() const { return RM; }

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: 

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: /// Returns the code model. The choices are small, kernel, medium, large, and

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: /// target default.

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: CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }

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: 

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: /// Get the IR-specified TLS model for Var.

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: static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {

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:   switch (GV->getThreadLocalMode()) {

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:   case GlobalVariable::NotThreadLocal:

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:     llvm_unreachable("getSelectedTLSModel for non-TLS variable");

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:     break;

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:   case GlobalVariable::GeneralDynamicTLSModel:

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:     return TLSModel::GeneralDynamic;

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:   case GlobalVariable::LocalDynamicTLSModel:

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:     return TLSModel::LocalDynamic;

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:   case GlobalVariable::InitialExecTLSModel:

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:     return TLSModel::InitialExec;

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:   case GlobalVariable::LocalExecTLSModel:

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:     return TLSModel::LocalExec;

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:   }

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:   llvm_unreachable("invalid TLS model");

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: }

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: 

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: bool TargetMachine::shouldAssumeDSOLocal(const Module &M,

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:                                          const GlobalValue *GV) const {

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:   // If the IR producer requested that this GV be treated as dso local, obey.

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:   if (GV && GV->isDSOLocal())

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:     return true;

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: 

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:   // If we are not supossed to use a PLT, we cannot assume that intrinsics are

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:   // local since the linker can convert some direct access to access via plt.

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:   if (M.getRtLibUseGOT() && !GV)

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:     return false;

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: 

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:   // According to the llvm language reference, we should be able to

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:   // just return false in here if we have a GV, as we know it is

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:   // dso_preemptable.  At this point in time, the various IR producers

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:   // have not been transitioned to always produce a dso_local when it

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:   // is possible to do so.

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:   // In the case of intrinsics, GV is null and there is nowhere to put

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:   // dso_local. Returning false for those will produce worse code in some

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:   // architectures. For example, on x86 the caller has to set ebx before calling

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:   // a plt.

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:   // As a result we still have some logic in here to improve the quality of the

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:   // generated code.

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:   // FIXME: Add a module level metadata for whether intrinsics should be assumed

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:   // local.

 (patrick  06-Apr-18) 

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: 

 (patrick  14-Jan-17) 

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:   Reloc::Model RM = getRelocationModel();

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:   const Triple &TT = getTargetTriple();

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: 

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:   // DLLImport explicitly marks the GV as external.

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:   if (GV && GV->hasDLLImportStorageClass())

 (patrick  23-Jun-19) 

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:     return false;

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: 

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:   // On MinGW, variables that haven't been declared with DLLImport may still

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:   // end up automatically imported by the linker. To make this feasible,

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:   // don't assume the variables to be DSO local unless we actually know

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:   // that for sure. This only has to be done for variables; for functions

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:   // the linker can insert thunks for calling functions from another DLL.

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:   if (TT.isWindowsGNUEnvironment() && GV && GV->isDeclarationForLinker() &&

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:       isa<GlobalVariable>(GV))

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:     return false;

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: 

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:   // Every other GV is local on COFF.

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:   // Make an exception for windows OS in the triple: Some firmware builds use

 (patrick  24-Jan-17) 

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:   // *-win32-macho triples. This (accidentally?) produced windows relocations

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:   // without GOT tables in older clang versions; Keep this behaviour.

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:   if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))

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:     return true;

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: 

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:   // Most PIC code sequences that assume that a symbol is local cannot

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:   // produce a 0 if it turns out the symbol is undefined. While this

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:   // is ABI and relocation depended, it seems worth it to handle it

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:   // here.

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:   if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())

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:     return false;

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: 

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:   if (GV && !GV->hasDefaultVisibility())

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:     return true;

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: 

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:   if (TT.isOSBinFormatMachO()) {

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:     if (RM == Reloc::Static)

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:       return true;

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:     return GV && GV->isStrongDefinitionForLinker();

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:   }

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: 

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:   assert(TT.isOSBinFormatELF());

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:   assert(RM != Reloc::DynamicNoPIC);

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: 

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:   bool IsExecutable =

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:       RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;

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:   if (IsExecutable) {

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:     // If the symbol is defined, it cannot be preempted.

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:     if (GV && !GV->isDeclarationForLinker())

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:       return true;

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: 

 (patrick  06-Apr-18) 

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:     // A symbol marked nonlazybind should not be accessed with a plt. If the

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:     // symbol turns out to be external, the linker will convert a direct

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:     // access to an access via the plt, so don't assume it is local.

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:     const Function *F = dyn_cast_or_null<Function>(GV);

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:     if (F && F->hasFnAttribute(Attribute::NonLazyBind))

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:       return false;

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: 

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:     bool IsTLS = GV && GV->isThreadLocal();

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:     bool IsAccessViaCopyRelocs =

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:         GV && Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);

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:     Triple::ArchType Arch = TT.getArch();

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:     bool IsPPC =

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:         Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;

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:     // Check if we can use copy relocations. PowerPC has no copy relocations.

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:     if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))

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:       return true;

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:   }

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: 

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:   // ELF supports preemption of other symbols.

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:   return false;

 (patrick  27-Jan-19) 

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: }

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: 

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: bool TargetMachine::useEmulatedTLS() const {

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:   // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls

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:   // was specified explicitly; otherwise uses target triple to decide default.

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:   if (Options.ExplicitEmulatedTLS)

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:     return Options.EmulatedTLS;

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:   return getTargetTriple().hasDefaultEmulatedTLS();

 (patrick  14-Jan-17) 

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: }

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: 

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: TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {

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:   bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;

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:   Reloc::Model RM = getRelocationModel();

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:   bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;

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:   bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);

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: 

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:   TLSModel::Model Model;

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:   if (IsSharedLibrary) {

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:     if (IsLocal)

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:       Model = TLSModel::LocalDynamic;

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:     else

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:       Model = TLSModel::GeneralDynamic;

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:   } else {

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:     if (IsLocal)

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:       Model = TLSModel::LocalExec;

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:     else

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:       Model = TLSModel::InitialExec;

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:   }

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: 

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:   // If the user specified a more specific model, use that.

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:   TLSModel::Model SelectedModel = getSelectedTLSModel(GV);

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:   if (SelectedModel > Model)

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:     return SelectedModel;

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: 

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:   return Model;

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: }

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: 

 (patrick  14-Jan-17) 

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: /// Returns the optimization level: None, Less, Default, or Aggressive.

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: CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }

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: 

 (patrick  14-Jan-17) 

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: void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }

 (pascal   03-Sep-16) 

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: 

 (patrick  06-Apr-18) 

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: TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) {

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:   return TargetTransformInfo(F.getParent()->getDataLayout());

 (pascal   03-Sep-16) 

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: }

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: 

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: void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,

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:                                       const GlobalValue *GV, Mangler &Mang,

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:                                       bool MayAlwaysUsePrivate) const {

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:   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {

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:     // Simple case: If GV is not private, it is not important to find out if

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:     // private labels are legal in this case or not.

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:     Mang.getNameWithPrefix(Name, GV, false);

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:     return;

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:   }

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:   const TargetLoweringObjectFile *TLOF = getObjFileLowering();

 (patrick  24-Jan-17) 

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:   TLOF->getNameWithPrefix(Name, GV, *this);

 (pascal   03-Sep-16) 

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: }

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: 

 (patrick  24-Jan-17) 

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: MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {

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:   const TargetLoweringObjectFile *TLOF = getObjFileLowering();

 (patrick  24-Jan-17) 

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:   SmallString<128> NameStr;

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:   getNameWithPrefix(NameStr, GV, TLOF->getMangler());

 (pascal   03-Sep-16) 

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:   return TLOF->getContext().getOrCreateSymbol(NameStr);

 (patrick  06-Apr-18) 

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: }

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: 

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: TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {

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:   // Since Analysis can't depend on Target, use a std::function to invert the

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:   // dependency.

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:   return TargetIRAnalysis(

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:       [this](const Function &F) { return this->getTargetTransformInfo(F); });

 (pascal   03-Sep-16) 

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: }