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and extern_weak_odr. These are the same as the non-odr versions, except that they indicate that the global will only be overridden by an *equivalent* global. In C, a function with weak linkage can be overridden by a function which behaves completely differently. This means that IP passes have to skip weak functions, since any deductions made from the function definition might be wrong, since the definition could be replaced by something completely different at link time. This is not allowed in C++, thanks to the ODR (One-Definition-Rule): if a function is replaced by another at link-time, then the new function must be the same as the original function. If a language knows that a function or other global can only be overridden by an equivalent global, it can give it the weak_odr linkage type, and the optimizers will understand that it is alright to make deductions based on the function body. The code generators on the other hand map weak and weak_odr linkage to the same thing. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66339 91177308-0d34-0410-b5e6-96231b3b80d8
170 lines
5.8 KiB
C++
170 lines
5.8 KiB
C++
//===-- DarwinTargetAsmInfo.cpp - Darwin asm properties ---------*- 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 defines target asm properties related what form asm statements
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// should take in general on Darwin-based targets
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Support/Mangler.h"
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#include "llvm/Target/DarwinTargetAsmInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetData.h"
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using namespace llvm;
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DarwinTargetAsmInfo::DarwinTargetAsmInfo(const TargetMachine &TM)
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: TargetAsmInfo(TM) {
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CStringSection_ = getUnnamedSection("\t.cstring",
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SectionFlags::Mergeable | SectionFlags::Strings);
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FourByteConstantSection = getUnnamedSection("\t.literal4\n",
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SectionFlags::Mergeable);
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EightByteConstantSection = getUnnamedSection("\t.literal8\n",
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SectionFlags::Mergeable);
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// Note: 16-byte constant section is subtarget specific and should be provided
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// there, if needed.
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SixteenByteConstantSection = 0;
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ReadOnlySection = getUnnamedSection("\t.const\n", SectionFlags::None);
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TextCoalSection =
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getNamedSection("\t__TEXT,__textcoal_nt,coalesced,pure_instructions",
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SectionFlags::Code);
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ConstTextCoalSection = getNamedSection("\t__TEXT,__const_coal,coalesced",
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SectionFlags::None);
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ConstDataCoalSection = getNamedSection("\t__DATA,__const_coal,coalesced",
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SectionFlags::None);
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ConstDataSection = getUnnamedSection(".const_data", SectionFlags::None);
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DataCoalSection = getNamedSection("\t__DATA,__datacoal_nt,coalesced",
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SectionFlags::Writeable);
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}
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/// emitUsedDirectiveFor - On Darwin, internally linked data beginning with
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/// the PrivateGlobalPrefix or the LessPrivateGlobalPrefix does not have the
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/// directive emitted (this occurs in ObjC metadata).
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bool
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DarwinTargetAsmInfo::emitUsedDirectiveFor(const GlobalValue* GV,
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Mangler *Mang) const {
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if (GV==0)
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return false;
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if (GV->hasLocalLinkage() && !isa<Function>(GV) &&
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((strlen(getPrivateGlobalPrefix()) != 0 &&
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Mang->getValueName(GV).substr(0,strlen(getPrivateGlobalPrefix())) ==
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getPrivateGlobalPrefix()) ||
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(strlen(getLessPrivateGlobalPrefix()) != 0 &&
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Mang->getValueName(GV).substr(0,strlen(getLessPrivateGlobalPrefix())) ==
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getLessPrivateGlobalPrefix())))
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return false;
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return true;
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}
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const Section*
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DarwinTargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV) const {
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SectionKind::Kind Kind = SectionKindForGlobal(GV);
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bool isWeak = GV->isWeakForLinker();
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bool isNonStatic = TM.getRelocationModel() != Reloc::Static;
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switch (Kind) {
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case SectionKind::Text:
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if (isWeak)
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return TextCoalSection;
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else
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return TextSection;
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case SectionKind::Data:
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case SectionKind::ThreadData:
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case SectionKind::BSS:
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case SectionKind::ThreadBSS:
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if (cast<GlobalVariable>(GV)->isConstant())
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return (isWeak ? ConstDataCoalSection : ConstDataSection);
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else
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return (isWeak ? DataCoalSection : DataSection);
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case SectionKind::ROData:
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return (isWeak ? ConstDataCoalSection :
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(isNonStatic ? ConstDataSection : getReadOnlySection()));
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case SectionKind::RODataMergeStr:
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return (isWeak ?
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ConstTextCoalSection :
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MergeableStringSection(cast<GlobalVariable>(GV)));
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case SectionKind::RODataMergeConst:
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return (isWeak ?
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ConstDataCoalSection:
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MergeableConstSection(cast<GlobalVariable>(GV)));
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default:
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assert(0 && "Unsuported section kind for global");
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}
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// FIXME: Do we have any extra special weird cases?
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return NULL;
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}
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const Section*
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DarwinTargetAsmInfo::MergeableStringSection(const GlobalVariable *GV) const {
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const TargetData *TD = TM.getTargetData();
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Constant *C = cast<GlobalVariable>(GV)->getInitializer();
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const Type *Ty = cast<ArrayType>(C->getType())->getElementType();
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unsigned Size = TD->getTypePaddedSize(Ty);
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if (Size) {
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unsigned Align = TD->getPreferredAlignment(GV);
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if (Align <= 32)
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return getCStringSection_();
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}
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return getReadOnlySection();
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}
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const Section*
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DarwinTargetAsmInfo::MergeableConstSection(const GlobalVariable *GV) const {
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Constant *C = GV->getInitializer();
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return MergeableConstSection(C->getType());
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}
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inline const Section*
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DarwinTargetAsmInfo::MergeableConstSection(const Type *Ty) const {
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const TargetData *TD = TM.getTargetData();
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unsigned Size = TD->getTypePaddedSize(Ty);
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if (Size == 4)
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return FourByteConstantSection;
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else if (Size == 8)
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return EightByteConstantSection;
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else if (Size == 16 && SixteenByteConstantSection)
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return SixteenByteConstantSection;
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return getReadOnlySection();
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}
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const Section*
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DarwinTargetAsmInfo::SelectSectionForMachineConst(const Type *Ty) const {
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const Section* S = MergeableConstSection(Ty);
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// Handle weird special case, when compiling PIC stuff.
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if (S == getReadOnlySection() &&
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TM.getRelocationModel() != Reloc::Static)
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return ConstDataSection;
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return S;
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}
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std::string
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DarwinTargetAsmInfo::UniqueSectionForGlobal(const GlobalValue* GV,
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SectionKind::Kind kind) const {
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assert(0 && "Darwin does not use unique sections");
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return "";
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}
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