reimplement Constant::ContainsRelocations as

Constant::getRelocationInfo(), which has a much simpler
to use API.  It still should not be part of libvmcore, but
is better than it was.  Also teach it to be smart about 
hidden visibility.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76700 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Constant.h

@@ -20,20 +20,6 @@ namespace llvm {
   template<typename T> class SmallVectorImpl;
   class LLVMContext;
 
-  /// If object contains references to other objects, then relocations are
-  /// usually required for emission of such object (especially in PIC mode). One
-  /// usually distinguishes local and global relocations. Local relocations are
-  /// made wrt objects in the same module and these objects have local (internal
-  /// or private) linkage. Global relocations are made wrt externally visible
-  /// objects. In most cases local relocations can be resolved via so-called
-  /// 'pre-link' technique.
-  namespace Reloc {
-    const unsigned None   = 0;
-    const unsigned Local  = 1 << 0; ///< Local relocations are required
-    const unsigned Global = 1 << 1; ///< Global relocations are required
-    const unsigned LocalOrGlobal = Local | Global;
-  }
-
 /// This is an important base class in LLVM. It provides the common facilities
 /// of all constant values in an LLVM program. A constant is a value that is
 /// immutable at runtime. Functions are constants because their address is
@@ -73,12 +59,21 @@ public:
   /// true for things like constant expressions that could divide by zero.
   bool canTrap() const;
 
-  /// ContainsRelocations - Return true if the constant value contains
-  /// relocations which cannot be resolved at compile time. Note that answer is
-  /// not exclusive: there can be possibility that relocations of other kind are
-  /// required as well.
-  bool ContainsRelocations(unsigned Kind = Reloc::LocalOrGlobal) const;
-
+  /// getRelocationInfo - This method classifies the entry according to
+  /// whether or not it may generate a relocation entry.  This must be
+  /// conservative, so if it might codegen to a relocatable entry, it should say
+  /// so.  The return values are:
+  /// 
+  ///  0: This constant pool entry is guaranteed to never have a relocation
+  ///     applied to it (because it holds a simple constant like '4').
+  ///  1: This entry has relocations, but the entries are guaranteed to be
+  ///     resolvable by the static linker, so the dynamic linker will never see
+  ///     them.
+  ///  2: This entry may have arbitrary relocations.
+  ///
+  /// FIXME: This really should not be in VMCore.
+  unsigned getRelocationInfo() const;
+  
   // Specialize get/setOperand for Constants as their operands are always
   // constants as well.
   Constant *getOperand(unsigned i) {

lib/CodeGen/MachineFunction.cpp

@@ -547,19 +547,7 @@ const Type *MachineConstantPoolEntry::getType() const {
 unsigned MachineConstantPoolEntry::getRelocationInfo() const {
   if (isMachineConstantPoolEntry())
     return Val.MachineCPVal->getRelocationInfo();
-  
-  // FIXME: This API sucks.
-  
-  // If no relocations, return 0.
-  if (!Val.ConstVal->ContainsRelocations())
-    return 0;
-
-  // If it contains no global relocations, return 1.
-  if (!Val.ConstVal->ContainsRelocations(Reloc::Global))
-    return 1;
-
-  // Otherwise, it has general relocations.
-  return 2;
+  return Val.ConstVal->getRelocationInfo();
 }
 
 MachineConstantPool::~MachineConstantPool() {

lib/Target/ELFTargetAsmInfo.cpp

@@ -54,20 +54,20 @@ ELFTargetAsmInfo::SectionKindForGlobal(const GlobalValue *GV) const {
 
   // Decide, whether we need data.rel stuff
   const GlobalVariable* GVar = dyn_cast<GlobalVariable>(GV);
-  if (GVar->hasInitializer()) {
+  if (GVar->hasInitializer() && TM.getRelocationModel() != Reloc::Static) {
     Constant *C = GVar->getInitializer();
     bool isConstant = GVar->isConstant();
     
-    
     // By default - all relocations in PIC mode would force symbol to be
     // placed in r/w section.
-    if (TM.getRelocationModel() != Reloc::Static &&
-        C->ContainsRelocations(Reloc::LocalOrGlobal))
-      return (C->ContainsRelocations(Reloc::Global) ?
-              (isConstant ?
-               SectionKind::DataRelRO : SectionKind::DataRel) :
-              (isConstant ?
-               SectionKind::DataRelROLocal : SectionKind::DataRelLocal));
+    switch (C->getRelocationInfo()) {
+    default: break;
+    case 1:
+      return isConstant ? SectionKind::DataRelROLocal :
+                          SectionKind::DataRelLocal;
+    case 2:
+      return isConstant ? SectionKind::DataRelRO : SectionKind::DataRel;
+    }
   }
 
   return Kind;

lib/Target/TargetAsmInfo.cpp

@@ -202,13 +202,13 @@ TargetAsmInfo::SectionKindForGlobal(const GlobalValue *GV) const {
 
   if (isSuitableForBSS(GVar)) {
     // Variable can be easily put to BSS section.
-    return (isThreadLocal ? SectionKind::ThreadBSS : SectionKind::BSS);
+    return isThreadLocal ? SectionKind::ThreadBSS : SectionKind::BSS;
   } else if (GVar->isConstant() && !isThreadLocal) {
     // Now we know, that variable has initializer and it is constant. We need to
     // check its initializer to decide, which section to output it into. Also
     // note, there is no thread-local r/o section.
     Constant *C = GVar->getInitializer();
-    if (C->ContainsRelocations(Reloc::LocalOrGlobal)) {
+    if (C->getRelocationInfo() != 0) {
       // Decide whether it is still possible to put symbol into r/o section.
       if (TM.getRelocationModel() != Reloc::Static)
         return SectionKind::Data;

lib/VMCore/Constants.cpp

@@ -101,34 +101,35 @@ bool Constant::canTrap() const {
   }
 }
 
-/// ContainsRelocations - Return true if the constant value contains relocations
-/// which cannot be resolved at compile time. Kind argument is used to filter
-/// only 'interesting' sorts of relocations.
-bool Constant::ContainsRelocations(unsigned Kind) const {
+
+/// getRelocationInfo - This method classifies the entry according to
+/// whether or not it may generate a relocation entry.  This must be
+/// conservative, so if it might codegen to a relocatable entry, it should say
+/// so.  The return values are:
+/// 
+///  0: This constant pool entry is guaranteed to never have a relocation
+///     applied to it (because it holds a simple constant like '4').
+///  1: This entry has relocations, but the entries are guaranteed to be
+///     resolvable by the static linker, so the dynamic linker will never see
+///     them.
+///  2: This entry may have arbitrary relocations.
+///
+/// FIXME: This really should not be in VMCore.
+unsigned Constant::getRelocationInfo() const {
   if (const GlobalValue* GV = dyn_cast<GlobalValue>(this)) {
-    bool isLocal = GV->hasLocalLinkage();
-    if ((Kind & Reloc::Local) && isLocal) {
-      // Global has local linkage and 'local' kind of relocations are
-      // requested
-      return true;
-    }
-
-    if ((Kind & Reloc::Global) && !isLocal) {
-      // Global has non-local linkage and 'global' kind of relocations are
-      // requested
-      return true;
-    }
-
-    return false;
+    if (GV->hasLocalLinkage() || GV->hasHiddenVisibility())
+      return 1;  // Local to this file/library.
+    return 2;    // Global reference.
   }
-
+  
+  unsigned Result = 0;
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
-    if (getOperand(i)->ContainsRelocations(Kind))
-      return true;
-
-  return false;
+    Result = std::max(Result, getOperand(i)->getRelocationInfo());
+  
+  return Result;
 }
 
+
 /// getVectorElements - This method, which is only valid on constant of vector
 /// type, returns the elements of the vector in the specified smallvector.
 /// This handles breaking down a vector undef into undef elements, etc.  For