Drop prelink support.

The way prelink used to work was

* The compiler decides if a given section only has relocations that
are know to point to the same DSO. If so, it names it
.data.rel.ro.local<something>.
* The static linker puts all of these together.
* The prelinker program assigns addresses to each library and resolves
the local relocations.

There are many problems with this:
* It is incompatible with address space randomization.
* The information passed by the compiler is redundant. The linker
knows if a given relocation is in the same DSO or not. If could sort
by that if so desired.
* There are newer ways of speeding up DSO (gnu hash for example).
* Even if we want to implement this again in the compiler, the previous
  implementation is pretty broken. It talks about relocations that are
  "resolved by the static linker". If they are resolved, there are none
  left for the prelinker. What one needs to track is if an expression
  will require only dynamic relocations that point to the same DSO.

At this point it looks like the prelinker is an historical curiosity.
For example, fedora has retired it because it failed to build for two
releases
(http://pkgs.fedoraproject.org/cgit/prelink.git/commit/?id=eb43100a8331d91c801ee3dcdb0a0bb9babfdc1f)

This patch removes support for it. That is, it stops printing the
".local" sections.

llvm-svn: 253280

1 files changed, 13 insertions, 29 deletions

diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index 5e614c6cb2e..fa6849fcfdc 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -816,42 +816,26 @@ Type *MachineConstantPoolEntry::getType() const {
   return Val.ConstVal->getType();
 }
 
-
-unsigned MachineConstantPoolEntry::getRelocationInfo() const {
+bool MachineConstantPoolEntry::needsRelocation() const {
   if (isMachineConstantPoolEntry())
-    return Val.MachineCPVal->getRelocationInfo();
-  return Val.ConstVal->getRelocationInfo();
+    return true;
+  return Val.ConstVal->needsRelocation();
 }
 
 SectionKind
 MachineConstantPoolEntry::getSectionKind(const DataLayout *DL) const {
-  SectionKind Kind;
-  switch (getRelocationInfo()) {
+  if (needsRelocation())
+    return SectionKind::getReadOnlyWithRel();
+  switch (DL->getTypeAllocSize(getType())) {
+  case 4:
+    return SectionKind::getMergeableConst4();
+  case 8:
+    return SectionKind::getMergeableConst8();
+  case 16:
+    return SectionKind::getMergeableConst16();
   default:
-    llvm_unreachable("Unknown section kind");
-  case Constant::GlobalRelocations:
-    Kind = SectionKind::getReadOnlyWithRel();
-    break;
-  case Constant::LocalRelocation:
-    Kind = SectionKind::getReadOnlyWithRelLocal();
-    break;
-  case Constant::NoRelocation:
-    switch (DL->getTypeAllocSize(getType())) {
-    case 4:
-      Kind = SectionKind::getMergeableConst4();
-      break;
-    case 8:
-      Kind = SectionKind::getMergeableConst8();
-      break;
-    case 16:
-      Kind = SectionKind::getMergeableConst16();
-      break;
-    default:
-      Kind = SectionKind::getReadOnly();
-      break;
-    }
+    return SectionKind::getReadOnly();
   }
-  return Kind;
 }
 
 MachineConstantPool::~MachineConstantPool() {