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e1cd93134f
There's no need for local symbols to go through the GOT, in fact it seems GNU ld is not even emitting GOT entries for local symbols and will error out when trying to resolve a GOT relocation for a local symbol. This bug triggers when bootstrapping clang on AArch64 Linux with -fPIC and the ARM64 backend. The AArch64 backend is not affected. With this commit it's now possible to bootstrap clang on AArch64 Linux with the ARM64 backend (-fPIC, -O3). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207226 91177308-0d34-0410-b5e6-96231b3b80d8
105 lines
4.1 KiB
C++
105 lines
4.1 KiB
C++
//===-- ARM64Subtarget.cpp - ARM64 Subtarget Information --------*- C++ -*-===//
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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 implements the ARM64 specific subclass of TargetSubtarget.
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//
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//===----------------------------------------------------------------------===//
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#include "ARM64InstrInfo.h"
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#include "ARM64Subtarget.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/CodeGen/MachineScheduler.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/Support/TargetRegistry.h"
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using namespace llvm;
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#define DEBUG_TYPE "arm64-subtarget"
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#define GET_SUBTARGETINFO_CTOR
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#define GET_SUBTARGETINFO_TARGET_DESC
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#include "ARM64GenSubtargetInfo.inc"
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ARM64Subtarget::ARM64Subtarget(const std::string &TT, const std::string &CPU,
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const std::string &FS, bool LittleEndian)
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: ARM64GenSubtargetInfo(TT, CPU, FS), ARMProcFamily(Others),
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HasFPARMv8(false), HasNEON(false), HasCrypto(false), HasCRC(false),
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HasZeroCycleRegMove(false), HasZeroCycleZeroing(false),
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CPUString(CPU), TargetTriple(TT), IsLittleEndian(LittleEndian) {
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// Determine default and user-specified characteristics
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if (CPUString.empty())
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CPUString = "generic";
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ParseSubtargetFeatures(CPUString, FS);
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}
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/// ClassifyGlobalReference - Find the target operand flags that describe
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/// how a global value should be referenced for the current subtarget.
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unsigned char
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ARM64Subtarget::ClassifyGlobalReference(const GlobalValue *GV,
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const TargetMachine &TM) const {
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// Determine whether this is a reference to a definition or a declaration.
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// Materializable GVs (in JIT lazy compilation mode) do not require an extra
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// load from stub.
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bool isDecl = GV->hasAvailableExternallyLinkage();
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if (GV->isDeclaration() && !GV->isMaterializable())
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isDecl = true;
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// MachO large model always goes via a GOT, simply to get a single 8-byte
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// absolute relocation on all global addresses.
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if (TM.getCodeModel() == CodeModel::Large && isTargetMachO())
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return ARM64II::MO_GOT;
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// The small code mode's direct accesses use ADRP, which cannot necessarily
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// produce the value 0 (if the code is above 4GB). Therefore they must use the
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// GOT.
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if (TM.getCodeModel() == CodeModel::Small && GV->isWeakForLinker() && isDecl)
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return ARM64II::MO_GOT;
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// If symbol visibility is hidden, the extra load is not needed if
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// the symbol is definitely defined in the current translation unit.
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// The handling of non-hidden symbols in PIC mode is rather target-dependent:
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// + On MachO, if the symbol is defined in this module the GOT can be
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// skipped.
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// + On ELF, the R_AARCH64_COPY relocation means that even symbols actually
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// defined could end up in unexpected places. Use a GOT.
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if (TM.getRelocationModel() != Reloc::Static && GV->hasDefaultVisibility()) {
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if (isTargetMachO())
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return (isDecl || GV->isWeakForLinker()) ? ARM64II::MO_GOT
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: ARM64II::MO_NO_FLAG;
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else
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// No need to go through the GOT for local symbols on ELF.
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return GV->hasLocalLinkage() ? ARM64II::MO_NO_FLAG : ARM64II::MO_GOT;
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}
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return ARM64II::MO_NO_FLAG;
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}
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/// This function returns the name of a function which has an interface
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/// like the non-standard bzero function, if such a function exists on
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/// the current subtarget and it is considered prefereable over
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/// memset with zero passed as the second argument. Otherwise it
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/// returns null.
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const char *ARM64Subtarget::getBZeroEntry() const {
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// At the moment, always prefer bzero.
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return "bzero";
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}
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void ARM64Subtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
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MachineInstr *begin, MachineInstr *end,
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unsigned NumRegionInstrs) const {
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// LNT run (at least on Cyclone) showed reasonably significant gains for
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// bi-directional scheduling. 253.perlbmk.
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Policy.OnlyTopDown = false;
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Policy.OnlyBottomUp = false;
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}
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