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cfc74b78b1
If a section is rw, it is irrelevant if the dynamic linker will write to it or not. It looks like llvm implemented this because gcc was doing it. It looks like gcc implemented this in the hope that it would put all the relocated items close together and speed up the dynamic linker. There are two problem with this: * It doesn't work. Both bfd and gold will map .data.rel to .data and concatenate the input sections in the order they are seen. * If we want a feature like that, it can be implemented directly in the linker since it knowns where the dynamic relocations are. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253436 91177308-0d34-0410-b5e6-96231b3b80d8
99 lines
3.7 KiB
C++
99 lines
3.7 KiB
C++
//===-- HexagonTargetObjectFile.cpp - Hexagon asm properties --------------===//
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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 contains the declarations of the HexagonTargetAsmInfo properties.
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//
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//===----------------------------------------------------------------------===//
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#include "HexagonTargetObjectFile.h"
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#include "HexagonSubtarget.h"
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#include "HexagonTargetMachine.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/ELF.h"
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using namespace llvm;
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static cl::opt<int> SmallDataThreshold("hexagon-small-data-threshold",
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cl::init(8), cl::Hidden,
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cl::desc("The maximum size of an object in the sdata section"));
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void HexagonTargetObjectFile::Initialize(MCContext &Ctx,
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const TargetMachine &TM) {
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TargetLoweringObjectFileELF::Initialize(Ctx, TM);
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InitializeELF(TM.Options.UseInitArray);
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SmallDataSection = getContext().getELFSection(
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".sdata", ELF::SHT_PROGBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
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SmallBSSSection = getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
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ELF::SHF_WRITE | ELF::SHF_ALLOC);
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}
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// sdata/sbss support taken largely from the MIPS Backend.
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static bool IsInSmallSection(uint64_t Size) {
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return Size > 0 && Size <= (uint64_t)SmallDataThreshold;
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}
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bool HexagonTargetObjectFile::IsSmallDataEnabled () const {
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return SmallDataThreshold > 0;
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}
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/// IsGlobalInSmallSection - Return true if this global value should be
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/// placed into small data/bss section.
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bool HexagonTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV,
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const TargetMachine &TM) const {
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// If the primary definition of this global value is outside the current
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// translation unit or the global value is available for inspection but not
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// emission, then do nothing.
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if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
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return false;
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// Otherwise, Check if GV should be in sdata/sbss, when normally it would end
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// up in getKindForGlobal(GV, TM).
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return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
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}
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/// IsGlobalInSmallSection - Return true if this global value should be
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/// placed into small data/bss section.
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bool HexagonTargetObjectFile::
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IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
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SectionKind Kind) const {
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// Only global variables, not functions.
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const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GV);
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if (!GVA)
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return false;
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if (Kind.isBSS() || Kind.isData() || Kind.isCommon()) {
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Type *Ty = GV->getType()->getElementType();
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return IsInSmallSection(
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GV->getParent()->getDataLayout().getTypeAllocSize(Ty));
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}
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return false;
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}
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MCSection *
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HexagonTargetObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
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SectionKind Kind, Mangler &Mang,
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const TargetMachine &TM) const {
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// Handle Small Section classification here.
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if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
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return SmallBSSSection;
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if (Kind.isData() && IsGlobalInSmallSection(GV, TM, Kind))
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return SmallDataSection;
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// Otherwise, we work the same as ELF.
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return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
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}
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