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[mips] Add the following MIPS options that control gp-relative addressing of

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small data items: -mgpopt, -mlocal-sdata, -mextern-sdata. Implement gp-relative
addressing for constants.

Differential Revision: http://reviews.llvm.org/D4903


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221450 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sasa Stankovic
2014-11-06 13:20:12 +00:00
parent ea60f51d87
commit 2b8f96996b
6 changed files with 112 additions and 43 deletions
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70
lib/Target/Mips/MipsTargetObjectFile.cpp
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@ -24,6 +24,17 @@ SSThreshold("mips-ssection-threshold", cl::Hidden,
cl::desc("Small data and bss section threshold size (default=8)"),
cl::init(8));
static cl::opt<bool>
LocalSData("mlocal-sdata", cl::Hidden,
cl::desc("MIPS: Use gp_rel for object-local data."),
cl::init(true));
static cl::opt<bool>
ExternSData("mextern-sdata", cl::Hidden,
cl::desc("MIPS: Use gp_rel for data that is not defined by the "
"current object."),
cl::init(true));
void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);
@ -37,29 +48,46 @@ void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
ELF::SHF_WRITE |ELF::SHF_ALLOC,
SectionKind::getBSS());
this->TM = &TM;
}
// A address must be loaded from a small section if its size is less than the
// small section size threshold. Data in this section must be addressed using
// gp_rel operator.
static bool IsInSmallSection(uint64_t Size) {
// gcc has traditionally not treated zero-sized objects as small data, so this
// is effectively part of the ABI.
return Size > 0 && Size <= SSThreshold;
}
bool MipsTargetObjectFile::IsGlobalInSmallSection(const GlobalValue *GV,
const TargetMachine &TM) const {
/// Return true if this global address should be placed into small data/bss
/// section.
bool MipsTargetObjectFile::
IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM) const {
// We first check the case where global is a declaration, because finding
// section kind using getKindForGlobal() is only allowed for global
// definitions.
if (GV->isDeclaration() || GV->hasAvailableExternallyLinkage())
return false;
return IsGlobalInSmallSectionImpl(GV, TM);
return IsGlobalInSmallSection(GV, TM, getKindForGlobal(GV, TM));
}
/// IsGlobalInSmallSection - Return true if this global address should be
/// placed into small data/bss section.
/// Return true if this global address should be placed into small data/bss
/// section.
bool MipsTargetObjectFile::
IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
SectionKind Kind) const {
return (IsGlobalInSmallSectionImpl(GV, TM) &&
(Kind.isDataRel() || Kind.isBSS() || Kind.isCommon()));
}
/// Return true if this global address should be placed into small data/bss
/// section. This method does all the work, except for checking the section
/// kind.
bool MipsTargetObjectFile::
IsGlobalInSmallSectionImpl(const GlobalValue *GV,
const TargetMachine &TM) const {
const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>();
// Return if small section is not available.
@ -71,13 +99,13 @@ IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
if (!GVA)
return false;
// We can only do this for datarel or BSS objects for now.
if (!Kind.isBSS() && !Kind.isDataRel())
// Enforce -mlocal-sdata.
if (!LocalSData && GV->hasLocalLinkage())
return false;
// If this is a internal constant string, there is a special
// section for it, but not in small data/bss.
if (Kind.isMergeable1ByteCString())
// Enforce -mextern-sdata.
if (!ExternSData && ((GV->hasExternalLinkage() && GV->isDeclaration()) ||
GV->hasCommonLinkage()))
return false;
Type *Ty = GV->getType()->getElementType();
@ -85,8 +113,6 @@ IsGlobalInSmallSection(const GlobalValue *GV, const TargetMachine &TM,
TM.getSubtargetImpl()->getDataLayout()->getTypeAllocSize(Ty));
}
const MCSection *MipsTargetObjectFile::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
@ -96,9 +122,27 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
// Handle Small Section classification here.
if (Kind.isBSS() && IsGlobalInSmallSection(GV, TM, Kind))
return SmallBSSSection;
if (Kind.isDataNoRel() && IsGlobalInSmallSection(GV, TM, Kind))
if (Kind.isDataRel() && IsGlobalInSmallSection(GV, TM, Kind))
return SmallDataSection;
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::SelectSectionForGlobal(GV, Kind, Mang,TM);
}
/// Return true if this constant should be placed into small data section.
bool MipsTargetObjectFile::
IsConstantInSmallSection(const Constant *CN, const TargetMachine &TM) const {
return (TM.getSubtarget<MipsSubtarget>().useSmallSection() &&
LocalSData &&
IsInSmallSection(TM.getSubtargetImpl()->getDataLayout()
->getTypeAllocSize(CN->getType())));
}
const MCSection *MipsTargetObjectFile::
getSectionForConstant(SectionKind Kind, const Constant *C) const {
if (IsConstantInSmallSection(C, *TM))
return SmallDataSection;
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::getSectionForConstant(Kind, C);
}