[MS][ARM64]: Hoist __ImageBase handling into TargetLoweringObjectFileCOFF::lowerRelativeReference, so that all COFF targets get this.

[arm-chrjan01]

Summary

Hoist __ImageBase handling into TargetLoweringObjectFileCOFF::lowerRelativeReference, so that all COFF targets get this. Do the same for getSectionForConstant.

[rnk]

lib/Target/AArch64/AArch64TargetObjectFile.cpp

82 ↗

(On Diff #149983)

Rather than duplicate this, I think we should hoist __ImageBase handling into TargetLoweringObjectFileCOFF::lowerRelativeReference, so that all COFF targets get this.

Also, do you think you'll need to do the same for getSectionForConstant?

[arm-chrjan01]

Refactored as per Reid's comment.

[rnk]

Needs a test. I think you can copy llvm/test/MC/COFF/ir-to-imgrel.ll to llvm/test/MC/AArch64/ and modify it accordingly. The test is kind of in the wrong location, though. It should really be in llvm/test/CodeGen/(X86|AArch64), since it's an llc test.

include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

167–168

This doesn't look like something clang-format would produce, consider running git clang-format to reformat the lines touched in the patch.

[arm-chrjan01]

Added test case. Fixed formatting in TargetLoweringObjectFileImpl.h.

[rnk]

lgtm

[arm-chrjan01]

Thank you for reviewing Reid. Please could you commit the change for me as I don't have commit rights.

include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

public:
   MCSection *getStaticDtorSection(unsigned Priority,
                                   const MCSymbol *KeySym) const override;
 
   void emitLinkerFlagsForGlobal(raw_ostream &OS,
                                 const GlobalValue *GV) const override;
 
   void emitLinkerFlagsForUsed(raw_ostream &OS,
                               const GlobalValue *GV) const override;
+
+  const MCExpr *
+    lowerRelativeReference(const GlobalValue *LHS, const GlobalValue *RHS,
+                           const TargetMachine &TM) const override;
+
+  /// Given a mergeable constant with the specified size and relocation
+  /// information, return a section that it should be placed in.
+  MCSection *getSectionForConstant(const DataLayout &DL, SectionKind Kind,
+                                   const Constant *C,
+                                   unsigned &Align) const override;
 };
 
 class TargetLoweringObjectFileWasm : public TargetLoweringObjectFile {
   mutable unsigned NextUniqueID = 0;
 
 public:
   TargetLoweringObjectFileWasm() = default;
   ~TargetLoweringObjectFileWasm() override = default;

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
   emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
 }
 
 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
     raw_ostream &OS, const GlobalValue *GV) const {
   emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
 }
 
+const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
+    const GlobalValue *LHS, const GlobalValue *RHS,
+    const TargetMachine &TM) const {
+  const Triple &T = TM.getTargetTriple();
+  if (!T.isKnownWindowsMSVCEnvironment() &&
+      !T.isWindowsItaniumEnvironment() &&
+      !T.isWindowsCoreCLREnvironment())
+    return nullptr;
+
+  // Our symbols should exist in address space zero, cowardly no-op if
+  // otherwise.
+  if (LHS->getType()->getPointerAddressSpace() != 0 ||
+      RHS->getType()->getPointerAddressSpace() != 0)
+    return nullptr;
+
+  // Both ptrtoint instructions must wrap global objects:
+  // - Only global variables are eligible for image relative relocations.
+  // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
+  // We expect __ImageBase to be a global variable without a section, externally
+  // defined.
+  //
+  // It should look something like this: @__ImageBase = external constant i8
+  if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
+      LHS->isThreadLocal() || RHS->isThreadLocal() ||
+      RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
+      cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
+    return nullptr;
+
+  return MCSymbolRefExpr::create(TM.getSymbol(LHS),
+                                 MCSymbolRefExpr::VK_COFF_IMGREL32,
+                                 getContext());
+}
+
+static std::string APIntToHexString(const APInt &AI) {
+  unsigned Width = (AI.getBitWidth() / 8) * 2;
+  std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
+  unsigned Size = HexString.size();
+  assert(Width >= Size && "hex string is too large!");
+  HexString.insert(HexString.begin(), Width - Size, '0');
+
+  return HexString;
+}
+
+static std::string scalarConstantToHexString(const Constant *C) {
+  Type *Ty = C->getType();
+  if (isa<UndefValue>(C)) {
+    return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
+  } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
+    return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
+  } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
+    return APIntToHexString(CI->getValue());
+  } else {
+    unsigned NumElements;
+    if (isa<VectorType>(Ty))
+      NumElements = Ty->getVectorNumElements();
+    else
+      NumElements = Ty->getArrayNumElements();
+    std::string HexString;
+    for (int I = NumElements - 1, E = -1; I != E; --I)
+      HexString += scalarConstantToHexString(C->getAggregateElement(I));
+    return HexString;
+  }
+}
+
+MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
+    const DataLayout &DL, SectionKind Kind, const Constant *C,
+    unsigned &Align) const {
+  if (Kind.isMergeableConst() && C) {
+    const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+                                     COFF::IMAGE_SCN_MEM_READ |
+                                     COFF::IMAGE_SCN_LNK_COMDAT;
+    std::string COMDATSymName;
+    if (Kind.isMergeableConst4()) {
+      if (Align <= 4) {
+        COMDATSymName = "__real@" + scalarConstantToHexString(C);
+        Align = 4;
+      }
+    } else if (Kind.isMergeableConst8()) {
+      if (Align <= 8) {
+        COMDATSymName = "__real@" + scalarConstantToHexString(C);
+        Align = 8;
+      }
+    } else if (Kind.isMergeableConst16()) {
+      if (Align <= 16) {
+        COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
+        Align = 16;
+      }
+    } else if (Kind.isMergeableConst32()) {
+      if (Align <= 32) {
+        COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
+        Align = 32;
+      }
+    }
+
+    if (!COMDATSymName.empty())
+      return getContext().getCOFFSection(".rdata", Characteristics, Kind,
+                                         COMDATSymName,
+                                         COFF::IMAGE_COMDAT_SELECT_ANY);
+  }
+
+  return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
+}
+
+
 //===----------------------------------------------------------------------===//
 //                                  Wasm
 //===----------------------------------------------------------------------===//
 
 static const Comdat *getWasmComdat(const GlobalValue *GV) {
   const Comdat *C = GV->getComdat();
   if (!C)
     return nullptr;

lib/Target/X86/X86TargetMachine.cpp

static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
   if (TT.isOSLinux() || TT.isOSNaCl() || TT.isOSIAMCU())
     return llvm::make_unique<X86LinuxNaClTargetObjectFile>();
   if (TT.isOSSolaris())
     return llvm::make_unique<X86SolarisTargetObjectFile>();
   if (TT.isOSFuchsia())
     return llvm::make_unique<X86FuchsiaTargetObjectFile>();
   if (TT.isOSBinFormatELF())
     return llvm::make_unique<X86ELFTargetObjectFile>();
-  if (TT.isKnownWindowsMSVCEnvironment() || TT.isWindowsCoreCLREnvironment())
-    return llvm::make_unique<X86WindowsTargetObjectFile>();
   if (TT.isOSBinFormatCOFF())
     return llvm::make_unique<TargetLoweringObjectFileCOFF>();
   llvm_unreachable("unknown subtarget type");
 }
 
 static std::string computeDataLayout(const Triple &TT) {
   // X86 is little endian
   std::string Ret = "e";

lib/Target/X86/X86TargetObjectFile.h

class X86LinuxNaClTargetObjectFile : public X86ELFTargetObjectFile {
     void Initialize(MCContext &Ctx, const TargetMachine &TM) override;
   };
 
   /// This implementation is used for Solaris on x86/x86-64.
   class X86SolarisTargetObjectFile : public X86ELFTargetObjectFile {
     void Initialize(MCContext &Ctx, const TargetMachine &TM) override;
   };
 
-  /// This implementation is used for Windows targets on x86 and x86-64.
-  class X86WindowsTargetObjectFile : public TargetLoweringObjectFileCOFF {
-    const MCExpr *
-    lowerRelativeReference(const GlobalValue *LHS, const GlobalValue *RHS,
-                           const TargetMachine &TM) const override;
-
-    /// Given a mergeable constant with the specified size and relocation
-    /// information, return a section that it should be placed in.
-    MCSection *getSectionForConstant(const DataLayout &DL, SectionKind Kind,
-                                     const Constant *C,
-                                     unsigned &Align) const override;
-  };
-
 } // end namespace llvm
 
 #endif

lib/Target/X86/X86TargetObjectFile.cpp

X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx,
   InitializeELF(TM.Options.UseInitArray);
 }
 
 void X86SolarisTargetObjectFile::Initialize(MCContext &Ctx,
                                             const TargetMachine &TM) {
   TargetLoweringObjectFileELF::Initialize(Ctx, TM);
   InitializeELF(TM.Options.UseInitArray);
 }
-
-const MCExpr *X86WindowsTargetObjectFile::lowerRelativeReference(
-    const GlobalValue *LHS, const GlobalValue *RHS,
-    const TargetMachine &TM) const {
-  // Our symbols should exist in address space zero, cowardly no-op if
-  // otherwise.
-  if (LHS->getType()->getPointerAddressSpace() != 0 ||
-      RHS->getType()->getPointerAddressSpace() != 0)
-    return nullptr;
-
-  // Both ptrtoint instructions must wrap global objects:
-  // - Only global variables are eligible for image relative relocations.
-  // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
-  // We expect __ImageBase to be a global variable without a section, externally
-  // defined.
-  //
-  // It should look something like this: @__ImageBase = external constant i8
-  if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
-      LHS->isThreadLocal() || RHS->isThreadLocal() ||
-      RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
-      cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
-    return nullptr;
-
-  return MCSymbolRefExpr::create(TM.getSymbol(LHS),
-                                 MCSymbolRefExpr::VK_COFF_IMGREL32,
-                                 getContext());
-}
-
-static std::string APIntToHexString(const APInt &AI) {
-  unsigned Width = (AI.getBitWidth() / 8) * 2;
-  std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
-  unsigned Size = HexString.size();
-  assert(Width >= Size && "hex string is too large!");
-  HexString.insert(HexString.begin(), Width - Size, '0');
-
-  return HexString;
-}
-
-static std::string scalarConstantToHexString(const Constant *C) {
-  Type *Ty = C->getType();
-  if (isa<UndefValue>(C)) {
-    return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
-  } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
-    return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
-  } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
-    return APIntToHexString(CI->getValue());
-  } else {
-    unsigned NumElements;
-    if (isa<VectorType>(Ty))
-      NumElements = Ty->getVectorNumElements();
-    else
-      NumElements = Ty->getArrayNumElements();
-    std::string HexString;
-    for (int I = NumElements - 1, E = -1; I != E; --I)
-      HexString += scalarConstantToHexString(C->getAggregateElement(I));
-    return HexString;
-  }
-}
-
-MCSection *X86WindowsTargetObjectFile::getSectionForConstant(
-    const DataLayout &DL, SectionKind Kind, const Constant *C,
-    unsigned &Align) const {
-  if (Kind.isMergeableConst() && C) {
-    const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
-                                     COFF::IMAGE_SCN_MEM_READ |
-                                     COFF::IMAGE_SCN_LNK_COMDAT;
-    std::string COMDATSymName;
-    if (Kind.isMergeableConst4()) {
-      if (Align <= 4) {
-        COMDATSymName = "__real@" + scalarConstantToHexString(C);
-        Align = 4;
-      }
-    } else if (Kind.isMergeableConst8()) {
-      if (Align <= 8) {
-        COMDATSymName = "__real@" + scalarConstantToHexString(C);
-        Align = 8;
-      }
-    } else if (Kind.isMergeableConst16()) {
-      if (Align <= 16) {
-        COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
-        Align = 16;
-      }
-    } else if (Kind.isMergeableConst32()) {
-      if (Align <= 32) {
-        COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
-        Align = 32;
-      }
-    }
-
-    if (!COMDATSymName.empty())
-      return getContext().getCOFFSection(".rdata", Characteristics, Kind,
-                                         COMDATSymName,
-                                         COFF::IMAGE_COMDAT_SELECT_ANY);
-  }
-
-  return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
-}