Imported Upstream version 5.18.0.246

Former-commit-id: 0c7ce5b1a7851e13f22acfd379b7f9fb304e4833

external/llvm/lib/Target/Mips/MipsTargetObjectFile.cpp

@@ -0,0 +1,194 @@
+//===-- MipsTargetObjectFile.cpp - Mips Object Files ----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MipsTargetObjectFile.h"
+#include "MipsSubtarget.h"
+#include "MipsTargetMachine.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Target/TargetMachine.h"
+using namespace llvm;
+
+static cl::opt<unsigned>
+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));
+
+static cl::opt<bool>
+EmbeddedData("membedded-data", cl::Hidden,
+             cl::desc("MIPS: Try to allocate variables in the following"
+                      " sections if possible: .rodata, .sdata, .data ."),
+             cl::init(false));
+
+void MipsTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM){
+  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
+  InitializeELF(TM.Options.UseInitArray);
+
+  SmallDataSection = getContext().getELFSection(
+      ".sdata", ELF::SHT_PROGBITS,
+      ELF::SHF_WRITE | ELF::SHF_ALLOC | ELF::SHF_MIPS_GPREL);
+
+  SmallBSSSection = getContext().getELFSection(".sbss", ELF::SHT_NOBITS,
+                                               ELF::SHF_WRITE | ELF::SHF_ALLOC |
+                                                   ELF::SHF_MIPS_GPREL);
+  this->TM = &static_cast<const MipsTargetMachine &>(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;
+}
+
+/// Return true if this global address should be placed into small data/bss
+/// section.
+bool MipsTargetObjectFile::IsGlobalInSmallSection(
+    const GlobalObject *GO, 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 (GO->isDeclaration() || GO->hasAvailableExternallyLinkage())
+    return IsGlobalInSmallSectionImpl(GO, TM);
+
+  return IsGlobalInSmallSection(GO, TM, getKindForGlobal(GO, TM));
+}
+
+/// Return true if this global address should be placed into small data/bss
+/// section.
+bool MipsTargetObjectFile::
+IsGlobalInSmallSection(const GlobalObject *GO, const TargetMachine &TM,
+                       SectionKind Kind) const {
+  return IsGlobalInSmallSectionImpl(GO, TM) &&
+         (Kind.isData() || Kind.isBSS() || Kind.isCommon() ||
+          Kind.isReadOnly());
+}
+
+/// 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 GlobalObject *GO,
+                           const TargetMachine &TM) const {
+  const MipsSubtarget &Subtarget =
+      *static_cast<const MipsTargetMachine &>(TM).getSubtargetImpl();
+
+  // Return if small section is not available.
+  if (!Subtarget.useSmallSection())
+    return false;
+
+  // Only global variables, not functions.
+  const GlobalVariable *GVA = dyn_cast<GlobalVariable>(GO);
+  if (!GVA)
+    return false;
+
+  // If the variable has an explicit section, it is placed in that section but
+  // it's addressing mode may change.
+  if (GVA->hasSection()) {
+    StringRef Section = GVA->getSection();
+
+    // Explicitly placing any variable in the small data section overrides
+    // the global -G value.
+    if (Section == ".sdata" || Section == ".sbss")
+      return true;
+
+    // Otherwise reject accessing it through the gp pointer. There are some
+    // historic cases which GCC doesn't appear to respect any more. These
+    // are .lit4, .lit8 and .srdata. For the moment reject these as well.
+    return false;
+  }
+
+  // Enforce -mlocal-sdata.
+  if (!LocalSData && GVA->hasLocalLinkage())
+    return false;
+
+  // Enforce -mextern-sdata.
+  if (!ExternSData && ((GVA->hasExternalLinkage() && GVA->isDeclaration()) ||
+                       GVA->hasCommonLinkage()))
+    return false;
+
+  // Enforce -membedded-data.
+  if (EmbeddedData && GVA->isConstant())
+    return false;
+
+  Type *Ty = GVA->getValueType();
+
+  // It is possible that the type of the global is unsized, i.e. a declaration
+  // of a extern struct. In this case don't presume it is in the small data
+  // section. This happens e.g. when building the FreeBSD kernel.
+  if (!Ty->isSized())
+    return false;
+
+  return IsInSmallSection(
+      GVA->getParent()->getDataLayout().getTypeAllocSize(Ty));
+}
+
+MCSection *MipsTargetObjectFile::SelectSectionForGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // TODO: Could also support "weak" symbols as well with ".gnu.linkonce.s.*"
+  // sections?
+
+  // Handle Small Section classification here.
+  if (Kind.isBSS() && IsGlobalInSmallSection(GO, TM, Kind))
+    return SmallBSSSection;
+  if (Kind.isData() && IsGlobalInSmallSection(GO, TM, Kind))
+    return SmallDataSection;
+  if (Kind.isReadOnly() && IsGlobalInSmallSection(GO, TM, Kind))
+    return SmallDataSection;
+
+  // Otherwise, we work the same as ELF.
+  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
+}
+
+/// Return true if this constant should be placed into small data section.
+bool MipsTargetObjectFile::IsConstantInSmallSection(
+    const DataLayout &DL, const Constant *CN, const TargetMachine &TM) const {
+  return (static_cast<const MipsTargetMachine &>(TM)
+              .getSubtargetImpl()
+              ->useSmallSection() &&
+          LocalSData && IsInSmallSection(DL.getTypeAllocSize(CN->getType())));
+}
+
+/// Return true if this constant should be placed into small data section.
+MCSection *MipsTargetObjectFile::getSectionForConstant(const DataLayout &DL,
+                                                       SectionKind Kind,
+                                                       const Constant *C,
+                                                       unsigned &Align) const {
+  if (IsConstantInSmallSection(DL, C, *TM))
+    return SmallDataSection;
+
+  // Otherwise, we work the same as ELF.
+  return TargetLoweringObjectFileELF::getSectionForConstant(DL, Kind, C, Align);
+}
+
+const MCExpr *
+MipsTargetObjectFile::getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
+  const MCExpr *Expr =
+      MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_None, getContext());
+  return MCBinaryExpr::createAdd(
+      Expr, MCConstantExpr::create(0x8000, getContext()), getContext());
+}